WorldWideScience

Sample records for strongly hydrophobic surface

  1. Water on a Hydrophobic surface

    Science.gov (United States)

    Scruggs, Ryan; Zhu, Mengjue; Poynor, Adele

    2012-02-01

    Hydrophobicity, meaning literally fear of water, is exhibited on the surfaces of non-stick cooking pans and water resistant clothing, on the leaves of the lotus plan, or even during the protein folding process in our bodies. Hydrophobicity is directly measured by determining a contact angle between water and an objects surface. Associated with a hydrophobic surface is the depletion layer, a low density region approximately 0.2 nm thick. We study this region by comparing data found in lab using surface plasmon resonance techniques to theoretical calculations. Experiments use gold slides coated in ODT and Mercapto solutions to model both hydrophobic and hydrophilic surfaces respectively.

  2. Wear resistance of hydrophobic surfaces

    Science.gov (United States)

    Martinez, MA; Abenojar, J.; Pantoja, M.; López de Armentia, S.

    2017-05-01

    Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance

  3. Liquid Water may Stick on Hydrophobic Surfaces

    Indian Academy of Sciences (India)

    IAS Admin

    Indian Institute of Technology Kharagpur, India. Liquid Water may Stick on Hydrophobic. Surfaces. Suman Chakraborty. Professor. Department of Mechanical Engineering, IIT Kharagpur, India. July, 2016 ...

  4. Characterisation of nanomaterial hydrophobicity using engineered surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal, E-mail: pascal.colpo@ec.europa.eu [Directorate Health, Consumer and Reference Materials, Consumer Products Safety Unit (Italy)

    2017-03-15

    Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors.

  5. Dynamics of Wetting of Ultra Hydrophobic Surfaces

    Science.gov (United States)

    Mohammad Karim, Alireza; Kim, Jeong-Hyun; Rothstein, Jonathan; Kavehpour, Pirouz; Mechanical and Industrial Engineering, University of Massachusetts, Amherst Collaboration

    2013-11-01

    Controlling the surface wettability of hydrophobic and super hydrophobic surfaces has extensive industrial applications ranging from coating, painting and printing technology and waterproof clothing to efficiency increase in power and water plants. This requires enhancing the knowledge about the dynamics of wetting on these hydrophobic surfaces. We have done experimental investigation on the dynamics of wetting on hydrophobic surfaces by looking deeply in to the dependency of the dynamic contact angles both advancing and receding on the velocity of the three-phase boundary (Solid/Liquid/Gas interface) using the Wilhelmy plate method with different ultra-hydrophobic surfaces. Several fluids with different surface tension and viscosity are used to study the effect of physical properties of liquids on the governing laws.

  6. Surface analysis of selected hydrophobic materials

    Science.gov (United States)

    Wisniewska, Sylwia Katarzyna

    This dissertation contains a series of studies on hydrophobic surfaces by various surface sensitive techniques such as contact angle measurements, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Hydrophobic surfaces have been classified as mineral surfaces, organic synthetic surfaces, or natural biological surfaces. As a model hydrophobic mineral surface, elemental sulfur has been selected. The sulfur surface has been characterized for selected allotropic forms of sulfur such as rhombic, monoclinic, plastic, and cyclohexasulfur. Additionally, dextrin adsorption at the sulfur surface was measured. The structure of a dextrin molecule showing hydrophobic sites has been presented to support the proposed hydrophobic bonding nature of dextrin adsorption at the sulfur surface. As a model organic hydrophobic surface, primary fatty amines such as dodecylamine, hexadecylamine, and octadecylamine were chosen. An increase of hydrophobicity, significant changes of infrared bands, and surface topographical changes with time were observed for each amine. Based on the results it was concluded that hydrocarbon chain rearrangement associated with recrystallization took place at the surface during contact with air. A barley straw surface was selected as a model of biological hydrophobic surfaces. The differences in the contact angles for various straw surfaces were explained by the presence of a wax layer. SEM images confirmed the heterogeneity and complexity of the wax crystal structure. AFM measurements provided additional structural details including a measure of surface roughness. Additionally, straw degradation as a result of conditioning in an aqueous environment was studied. Significant contact angle changes were observed as soon as one day after conditioning. FTIR studies showed a gradual wax layer removal due to straw surface decomposition. SEM and AFM images revealed topographical changes and biological

  7. Surface Hydrophobicity Causes SO2 Tolerance in Lichens

    Science.gov (United States)

    Hauck, Markus; Jürgens, Sascha-René; Brinkmann, Martin; Herminghaus, Stephan

    2008-01-01

    Background and Aims The superhydrophobicity of the thallus surface in one of the most SO2-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO2. The study described here tests this hypothesis. Methods Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO2 tolerance and contact angles were measured to quantify hydrophobicity. Key Results The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO2 tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli. Conclusions Surface hydrophobicity is the main factor controlling SO2 tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO2 also explains why many markedly SO2-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals. PMID:18077467

  8. Liquid Water may Stick on Hydrophobic Surfaces

    Indian Academy of Sciences (India)

    IAS Admin

    The behavior of fluid on a solid surface under static and dynamic conditions are usually clubbed together. • On a wetting surface (hydrophilic), liquid water is believed to adhere to the surface causing multilayer sticking. • On a non-wetting surface (hydrophobic), water is believed to glide across the surface leading to slip ...

  9. Water on hydrophobic surfaces: Mechanistic modeling of hydrophobic interaction chromatography.

    Science.gov (United States)

    Wang, Gang; Hahn, Tobias; Hubbuch, Jürgen

    2016-09-23

    Mechanistic models are successfully used for protein purification process development as shown for ion-exchange column chromatography (IEX). Modeling and simulation of hydrophobic interaction chromatography (HIC) in the column mode has been seldom reported. As a combination of these two techniques is often encountered in biopharmaceutical purification steps, accurate modeling of protein adsorption in HIC is a core issue for applying holistic model-based process development, especially in the light of the Quality by Design (QbD) approach. In this work, a new mechanistic isotherm model for HIC is derived by consideration of an equilibrium between well-ordered water molecules and bulk-like ordered water molecules on the hydrophobic surfaces of protein and ligand. The model's capability of describing column chromatography experiments is demonstrated with glucose oxidase, bovine serum albumin (BSA), and lysozyme on Capto™ Phenyl (high sub) as model system. After model calibration from chromatograms of bind-and-elute experiments, results were validated with batch isotherms and prediction of further gradient elution chromatograms. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Switchable Hydrophobic-Hydrophilic Surfaces

    CERN Document Server

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

    2002-01-01

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

  11. Hydrophobic Calcium Carbonate for Cement Surface

    Directory of Open Access Journals (Sweden)

    Shashi B. Atla

    2017-12-01

    Full Text Available This report describes a novel way to generate a highly effective hydrophobic cement surface via a carbonation route using sodium stearate. Carbonation reaction was carried out at different temperatures to investigate the hydrophobicity and morphology of the calcium carbonate formed with this process. With increasing temperatures, the particles changed from irregular shapes to more uniform rod-like structures and then aggregated to form a plate-like formation. The contact angle against water was found to increase with increasing temperature; after 90 °C there was no further increase. The maximum contact angle of 129° was obtained at the temperature of 60 °C. It was also found that carbonation increased the micro hardness of the cement material. The micro hardness was found to be dependent on the morphology of the CaCO3 particles. The rod like structures which caused increased mineral filler produced a material with enhanced strength. The 13C cross polarization magic-angle spinning NMR spectra gave plausible explanation of the interaction of organic-inorganic moieties.

  12. The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

    2004-01-01

    Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...

  13. Surfactant Facilitated Spreading of Aqueous Drops on Hydrophobic Surfaces

    Science.gov (United States)

    Kumar, Nitin; Couzis, Alex; Maldareili, Charles; Singh, Bhim (Technical Monitor)

    2001-01-01

    Microgravity technologies often require aqueous phases to spread over nonwetting hydrophobic solid surfaces. Surfactants facilitate the wetting of water on hydrophobic surfaces by adsorbing on the water/air and hydrophobic solid/water interfaces and lowering the surface tensions of these interfaces. The tension reductions decrease the contact angle, which increases the equilibrium wetted area. Hydrocarbon surfactants; (i.e., amphiphiles with a hydrophobic moiety consisting of an extended chain of (aliphatic) methylene -CH2- groups attached to a large polar group to give aqueous solubility) are capable of reducing the contact angles on surfaces which are not very hydrophobic, but do not reduce significantly the contact angles of the very hydrophobic surfaces such as parafilm, polyethylene or self assembled monolayers. Trisiloxane surfactants (amphiphiles with a hydrophobe consisting of methyl groups linked to a trisiloxane backbone in the form of a disk ((CH3)3-Si-O-Si-O-Si(CH3)3) and an extended ethoxylate (-(OCH2CH2)a-) polar group in the form of a chain with four or eight units) can significantly reduce the contact angle of water on a very hydrophobic surface and cause rapid and complete (or nearly complete) spreading (termed superspreading). The overall goal of the research described in this proposal is to establish and verify a theory for how trisiloxanes cause superspreading, and then use this knowledge as a guide to developing more general hydrocarbon based surfactant systems which superspread. We propose that the trisiloxane surfactants superspread because their structure allows them to strongly lower the high hydrophobic solid/aqueous tension when they adsorb to the solid surface. When the siloxane adsorbs, the hydrophobic disk parts of the molecule adsorb onto the surface removing the surface water. Since the cross-sectional area of the disk is larger than that of the extended ethoxylate chain, the disks can form a space-filling mat on the surface which

  14. Patterned hydrophobic and hydrophilic surfaces of ultra-smooth nanocrystalline diamond layers

    Energy Technology Data Exchange (ETDEWEB)

    Mertens, M., E-mail: michael.mertens@uni-ulm.de [Institute of Micro and Nanomaterials, Ulm University, 89081 Ulm (Germany); Mohr, M.; Brühne, K.; Fecht, H.J. [Institute of Micro and Nanomaterials, Ulm University, 89081 Ulm (Germany); Łojkowski, M.; Święszkowski, W. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Łojkowski, W. [Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw (Poland)

    2016-12-30

    Highlights: • Hydrophobic and hydrophilic properties on fluorine-, hydrogen- and oxygen- terminated ultra-nanocrystalline diamond films. • Micropatterned - multi-terminated layers with both hydrophobic and hydrophilic areas on one sample. • Visualization of multi-terminated surfaces by e.g. SEM and LFM. • Roughness and friction investigations on different terminated surfaces. • Smooth and biocompatible surfaces with same roughness regardless of hydrophobicity for microbiological investigations. - Abstract: In this work, we show that ultra nanocrystalline diamond (UNCD) surfaces have been modified to add them hydrophobic and hydrophilic properties. The nanocrystalline diamond films were deposited using the hot filament chemical vapor deposition (HFCVD) technique. This allows growing diamond on different substrates which can be even 3D or structured. Silicon and, for optical applications, transparent quartz glass are the preferred substrates for UNCD layers growth. Fluorine termination leads to strong hydrophobic properties as indicated by a high contact angle for water of more than 100°. Hydrogen termination shows lesser hydrophobic behavior. Hydrophilic characteristics has been realised with oxygen termination. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) measurements confirm the oxygen and fluorine- termination on the nanocrystalline diamond surface. Further, by micropatterning using photolithography, multi-terminated layers have been created with both hydrophobic and hydrophilic areas. In addition, we have shown that retermination is achieved, and the properties of the surface have been changed from hydrophobic to hydrophilic and vice versa. Micro- roughness and stress in the grown film influences slightly the wetting angle as well. The opportunity to realize local differences in hydrophobicity on nanocrystalline diamond layers, in any size or geometry, offers interesting applications for example in

  15. Molecular explanation for why talc surfaces can be both hydrophilic and hydrophobic.

    Science.gov (United States)

    Rotenberg, Benjamin; Patel, Amish J; Chandler, David

    2011-12-21

    While individual water molecules adsorb strongly on a talc surface (hydrophilic behavior), a droplet of water beads up on the same surface (hydrophobic behavior). To rationalize this dichotomy, we investigated the influence of the microscopic structure of the surface and the strength of adhesive (surface-water) interactions on surface hydrophobicity. We have shown that at low relative humidity, the competition between adhesion and the favorable entropy of being in the vapor phase determines the surface coverage. However, at saturation, it is the competition between adhesion and cohesion (water-water interactions) that determines the surface hydrophobicity. The adhesive interactions in talc are strong enough to overcome the unfavorable entropy, and water adsorbs strongly on talc surfaces. However, they are too weak to overcome the cohesive interactions, and water thus beads up on talc surfaces. Surprisingly, even talc-like surfaces that are highly adhesive do not fully wet at saturation. Instead, a water droplet forms on top of a strongly adsorbed monolayer of water. Our results imply that the interior of hydrophobic zeolites suspended in water may contain adsorbed water molecules at pressures much lower than the intrusion pressure. © 2011 American Chemical Society

  16. Wood Nanotechnology for Strong, Mesoporous, and Hydrophobic Biocomposites for Selective Separation of Oil/Water Mixtures.

    Science.gov (United States)

    Fu, Qiliang; Ansari, Farhan; Zhou, Qi; Berglund, Lars A

    2018-03-27

    Tremendous efforts have been dedicated to developing effective and eco-friendly approaches for separation of oil-water mixtures. Challenges remain in terms of complex processing, high material cost, low efficiency, and scale-up problems. Inspired by the tubular porosity and hierarchical organization of wood, a strong, mesoporous, and hydrophobic three-dimensional wood structure is created for selective oil/water separation. A delignified wood template with hydrophilic characteristics is obtained by removal of lignin. The delignified wood template is further functionalized by a reactive epoxy-amine system. This wood/epoxy biocomposite reveals hydrophobic/oleophilic functionality and shows oil absorption as high as 15 g/g. The wood/epoxy biocomposite has a compression yield strength and modulus up to 18 and 263 MPa, respectively, at a solid volume fraction of only 12%. This is more than 20 times that of cellulose-based foams/aerogels reconstructed from cellulose nanofibrils. The favorable performance is ascribed to the natural hierarchical honeycomb structure of wood. Oil can be selectively absorbed not only from below but also from above the water surface. High oil/water absorption capacity of both types of wood structures (delignified template and polymer-modified biocomposite) allows for applications in oil/water separation.

  17. Design of textured surfaces for super-hydrophobicity

    Indian Academy of Sciences (India)

    Although the Cassie–Baxter and Wenzel equations predict contact angles for relative dimensions of micro-pillars on textured surfaces, the absolute pillar dimensions are determined by trial and error. Alternatively, geometries of natural super-hydrophobic surfaces are often imitated to design textured surfaces. Knowing the ...

  18. Ice friction: The effects of surface roughness, structure, and hydrophobicity

    Science.gov (United States)

    Kietzig, Anne-Marie; Hatzikiriakos, Savvas G.; Englezos, Peter

    2009-07-01

    The effect of surface roughness, structure, and hydrophobicity on ice friction is studied systematically over a wide range of temperature and sliding speeds using several metallic interfaces. Hydrophobicity in combination with controlled roughness at the nanoscale is achieved by femtosecond laser irradiation to mimic the lotus effect on the slider's surface. The controlled roughness significantly increases the coefficient of friction at low sliding speeds and temperatures well below the ice melting point. However, at temperatures close to the melting point and relatively higher speeds, roughness and hydrophobicity significantly decrease ice friction. This decrease in friction is mainly due to the suppression of capillary bridges in spite of the presence of surface asperities that facilitate their formation. Finally, grooves oriented in the sliding direction also significantly decrease friction in the low velocity range compared to scratches and grooves randomly distributed over a surface.

  19. Design of textured surfaces for super-hydrophobicity

    Indian Academy of Sciences (India)

    Prithvi Raj Jelia

    2017-11-11

    Nov 11, 2017 ... viour of a droplet on super-hydrophobic surfaces, an ana- lytical model is proposed in which a single droplet is assumed to rest on a surface bearing an array of square pillars. The objective of the model is to optimize the a b c. Figure 1. Model showing microscopic square pillars arranged in square array.

  20. Design of surface hierarchy for extreme hydrophobicity.

    Science.gov (United States)

    Kwon, Yongjoo; Patankar, Neelesh; Choi, Junkyu; Lee, Junghoon

    2009-06-02

    An extreme water-repellent surface is designed and fabricated with a hierarchical integration of nano- and microscale textures. We combined the two readily accessible etching techniques, a standard deep silicon etching, and a gas phase isotropic etching (XeF2) for the uniform formation of double roughness on a silicon surface. The fabricated synthetic surface shows the hallmarks of the Lotus effect: durable super water repellency (contact angle>173 degrees) and the sole existence of the Cassie state even with a very large spacing between roughness structures (>1:7.5). We directly demonstrate the absence of the Wenzel's or wetted state through a series of experiments. When a water droplet is squeezed or dropped on the fabricated surface, the contact angle hardly changes and the released droplet instantly springs back without remaining wetted on the surface. We also show that a ball of water droplet keeps bouncing on the surface. Furthermore, the droplet shows very small contact angle hysteresis which can be further used in applications such as super-repellent coating and low-drag microfludics. These properties are attributed to the nano/micro surface texture designed to keep the nonwetting state energetically favorable.

  1. Modification of epoxy resin, silicon and glass surfaces with alkyl- or fluoroalkylsilanes for hydrophobic properties

    Energy Technology Data Exchange (ETDEWEB)

    Marczak, Jacek, E-mail: jacek.marczak@eitplus.pl [Wroclaw Research Centre EIT+ Ltd., 147 Stablowicka St., 54-066 Wrocław (Poland); Kargol, Marta [Wroclaw Research Centre EIT+ Ltd., 147 Stablowicka St., 54-066 Wrocław (Poland); Psarski, Maciej; Celichowski, Grzegorz [Department of Materials Technology and Chemistry, University of Lodz, Pomorska 163, 90-236 Lodz (Poland)

    2016-09-01

    Graphical abstract: - Highlights: • Chemical structure of alkylsilanes and fluoroalkylsilanes can affect the hydrophobic and surface performance of the modified samples. • Wet chemical hydrophobization is relatively simple and inexpensive method to obtain hydrophobic/superhydrophobic coatings. • The samples degradation is not observed and hydrophobic coatings seem to be stable in UV light. - Abstract: Preparation of superhydrophobic materials inspired by nature has attracted a great scientific interest in recent decades. Some of these materials have hierarchical lotus-like structures, i.e. micro- and nano-objects coated by hydrophobic compounds. A major challenge of applying the superhydrophobic surfaces for the self-cleaning coatings preparation is their improved efficiency in varying atmospheric conditions, e.g. UV light. The objective of this research work was to investigate the effect of the different chemical structure and the surface free energy on the hydrophobic and tribological properties of the alkylsilanes and fluoroalkylsilanes deposited on silicon wafers, glass slides and epoxy resin. Tribological and hydrophobic properties of the modified surfaces were correlated with their chemical structures. Chemical structures of the deposited materials were examined by using Fourier transform infrared (FT-IR) spectroscopy and hydrophobic properties were investigated by water contact angle (WCA) and surface free energy (SFE) measurements. The modified surfaces exhibited water contact angles of above 100° for the selected modifiers. It was noticed that the replacement of hydrogen atoms by fluorine atoms in alkyl chain caused an increase in the water contact angle values and a decrease in friction coefficients. The obtained results showed that the carbon chain length of a modifier and its chemical structure can strongly affect the hydrophobic and tribological properties of the modified surfaces. The highest values of WCA, lowest values of SFE and coefficient

  2. Modification of epoxy resin, silicon and glass surfaces with alkyl- or fluoroalkylsilanes for hydrophobic properties

    International Nuclear Information System (INIS)

    Marczak, Jacek; Kargol, Marta; Psarski, Maciej; Celichowski, Grzegorz

    2016-01-01

    Graphical abstract: - Highlights: • Chemical structure of alkylsilanes and fluoroalkylsilanes can affect the hydrophobic and surface performance of the modified samples. • Wet chemical hydrophobization is relatively simple and inexpensive method to obtain hydrophobic/superhydrophobic coatings. • The samples degradation is not observed and hydrophobic coatings seem to be stable in UV light. - Abstract: Preparation of superhydrophobic materials inspired by nature has attracted a great scientific interest in recent decades. Some of these materials have hierarchical lotus-like structures, i.e. micro- and nano-objects coated by hydrophobic compounds. A major challenge of applying the superhydrophobic surfaces for the self-cleaning coatings preparation is their improved efficiency in varying atmospheric conditions, e.g. UV light. The objective of this research work was to investigate the effect of the different chemical structure and the surface free energy on the hydrophobic and tribological properties of the alkylsilanes and fluoroalkylsilanes deposited on silicon wafers, glass slides and epoxy resin. Tribological and hydrophobic properties of the modified surfaces were correlated with their chemical structures. Chemical structures of the deposited materials were examined by using Fourier transform infrared (FT-IR) spectroscopy and hydrophobic properties were investigated by water contact angle (WCA) and surface free energy (SFE) measurements. The modified surfaces exhibited water contact angles of above 100° for the selected modifiers. It was noticed that the replacement of hydrogen atoms by fluorine atoms in alkyl chain caused an increase in the water contact angle values and a decrease in friction coefficients. The obtained results showed that the carbon chain length of a modifier and its chemical structure can strongly affect the hydrophobic and tribological properties of the modified surfaces. The highest values of WCA, lowest values of SFE and coefficient

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

    Science.gov (United States)

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

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Influence of hydrophobic surface treatment toward performance of air filter

    Science.gov (United States)

    Shahfiq Zulkifli, Nazrul; Zaini Yunos, Muhamad; Ahmad, Azlinnorazia; Harun, Zawati; Akhair, Siti Hajar Mohd; Adibah Raja Ahmad, Raja; Hafeez Azhar, Faiz; Rashid, Abdul Qaiyyum Abd; Ismail, Al Emran

    2017-08-01

    This study investigated the performance of hydrophobic surface treatment by using silica aerogel powder via spray coating techniques. Hydrophobic properties were determined by measuring the level of the contact angle. Meanwhile, performance was evaluated in term of the hydrogen gas flow and humidity rejection. The results are shown by contact angle that the microstructure filter, especially in the upper layer and sub-layer has been changed. The results also show an increase of hydrophobicity due to the increased quantity of silica aerogel powder. Results also showed that the absorption and rejection filter performance filter has increased after the addition of silica aerogel powder. The results showed that with the addition of 5 grams of powder of silica aerogel have the highest result of wetting angle 134.11°. The highest humidity rejection found with 5 grams of powder of silica aerogel.

  5. Electrophoresis of a polarizable charged colloid with hydrophobic surface: A numerical study

    Science.gov (United States)

    Bhattacharyya, Somnath; Majee, Partha Sarathi

    2017-04-01

    We consider the electrophoresis of a charged colloid for a generalized situation in which the particle is considered to be polarizable and the surface exhibits hydrophobicity. The dielectric polarization of the particle creates a nonlinear dependence of the electrophoretic velocity on the applied electric field, and the core hydrophobicity amplifies the fluid convection in the Debye layer. Thus, a linear analysis is no longer applicable for this situation. The present analysis is based on the numerical solution of the nonlinear electrokinetic equations based on the Navier-Stokes-Nernst-Planck-Poisson equations coupled with the Laplace equation for the electric field within the dielectric particle. The hydrophobicity of the particle may influence its electric polarization by enhancing the convective transport of ions. The nonlinear effects, such as double-layer polarization and relaxation, are also influenced by the hydrophobicity of the particle surface. The present results compare well for a lower range of the applied electric field and surface charge density with the existing results for a perfectly dielectric particle with a hydrophobic surface based on the first-order perturbation analysis due to Khair and Squires [Phys. Fluids 21, 042001 (2009), 10.1063/1.3116664]. Dielectric polarization creates a reduction in particle electrophoretic velocity, and its impact is strong for a moderate range of Debye length. A quantitative measure of the nonlinear effects is demonstrated by comparing the electrophoretic velocity with an existing linear model.

  6. High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects

    Science.gov (United States)

    Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2009-08-01

    A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.

  7. Behavior of a Liquid Bridge between Nonparallel Hydrophobic Surfaces.

    Science.gov (United States)

    Ataei, Mohammadmehdi; Chen, Huanchen; Amirfazli, Alidad

    2017-12-26

    When a liquid bridge is formed between two nonparallel identical surfaces, it can move along the surfaces. Literature indicates that the direction of bridge movement is governed by the wettability of surfaces. When the surfaces are hydrophilic, the motion of the bridge is always toward the cusp (intersection of the plane of the two bounding surfaces). On the other hand, the movement is hitherto thought to be always pointing away from the cusp when the surfaces are hydrophobic. In this study, through experiments, numerical simulations, and analytical reasoning, we demonstrate that for hydrophobic surfaces, wettability is not the only factor determining the direction of the motion. A new geometrical parameter, i.e., confinement (cf), was defined as the ratio of the distance of the farthest contact point of the bridge to the cusp, and that of the closest contact point to the cusp. The direction of the motion depends on the amount of confinement (cf). When the distance between the surfaces is large (resulting in a small cf), the bridge tends to move toward the cusp through a pinning/depinning mechanism of contact lines. When the distance between the surfaces is small (large cf), the bridge tends to move away from the cusp. For a specific system, a maximum cf value (cf max ) exists. A sliding behavior (i.e., simultaneous advancing on the wider side and receding on the narrower side) can also be seen when a liquid bridge is compressed such that the cf exceeds the cf max . Contact angle hysteresis (CAH) is identified as an underpinning phenomenon that together with cf fundamentally explains the movement of a trapped liquid between two hydrophobic surfaces. If there is no CAH, however, i.e., the case of ideal hydrophobic surfaces, the cf will be a constant; we show that the bridge slides toward the cusp when it is stretched, while it slides away from the cusp when it is compressed (note sliding motion is different from motion due to pinning/depinning mechanism of contact

  8. INVESTIGATION OF MICRO AND NANOSTRUCTURE OF HYDROPHOBIC PLANTS SURFACE

    OpenAIRE

    M. V. Zhukov

    2014-01-01

    Micro and nanostructure of petals and flowers of pink rose family having super hydrophobic phenomenon known as "lotus effect" was studied by optical and scanning probe microscopy. Quasi-ordered corrugated structure was found on the surface of the rose petals. It represents the ensemble of smoothed shape peaks like a lotus leaf structure. Structure saving during dehydration of rose petal (for 5 days) by drying in the air under normal conditions was found, the difference is apparent in the dens...

  9. Fluctuations of water near extended hydrophobic and hydrophilic surfaces

    OpenAIRE

    Patel, Amish J.; Chandler, David

    2009-01-01

    We use molecular dynamics simulations of the SPC-E model of liquid water to derive probability distributions for water density fluctuations in probe volumes of different shapes and sizes, both in the bulk as well as near hydrophobic and hydrophilic surfaces. To obtain our results, we introduce a biased sampling of coarse-grained densities, which in turn biases the actual solvent density. The technique is easily combined with molecular dynamics integration algorithms. Our principal result is t...

  10. Theoretical analysis of adsorption thermodynamics for hydrophobic peptide residues on SAM surfaces of varying functionality.

    Science.gov (United States)

    Latour, Robert A; Rini, Christopher J

    2002-06-15

    At a fundamental level, protein adsorption to a synthetic surface must be strongly influenced by the interaction between the peptide residues presented by the protein's surface (primary protein structure) and the functional groups presented by the synthetic surface. In this study, semi-empirical molecular modeling was used along with experimental wetting data to theoretically approach protein adsorption at this primary structural level. Changes in enthalpy, entropy, and Gibbs free energy were calculated as a function of residue-surface separation distance for the adsorption of individual hydrophobic peptide residues (valine, leucine, phenylalanine) on alkanethiol self-assembled monolayers on gold [Au-S(CH(2))(15)-X; X = CH(3), OH, NH(3)(+), COO(-)]. The results predict that the adsorption of each type of hydrophobic residue is energetically favorable and entropy dominated on a methyl-terminated hydrophobic surface, energetically unfavorable and enthalpy dominated on a hydroxyl-terminated neutral hydrophilic surface, and very slightly favorable to unfavorable and enthalpy dominated on charged surfaces. These theoretical results provide a basis for understanding some of the fundamental effects governing protein adsorption to synthetic surfaces. This level of understanding is needed for the proactive design of surfaces to control protein adsorption and subsequent cellular response for both implant and tissue engineering applications. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 564-577, 2002

  11. Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfaces

    DEFF Research Database (Denmark)

    Hansson, Petra M; Claesson, Per M.; Swerin, Agne

    2013-01-01

    Friction forces have long been associated with the famous Amontons' rule that states that the friction force is linearly dependent on the applied normal load, with the proportionality constant being known as the friction coefficient. Amontons' rule is however purely phenomenological and does...... not in itself provide any information on why the friction coefficient is different for different material combinations. In this study, friction forces between a colloidal probe and nanostructured particle coated surfaces in an aqueous environment exhibiting different roughness length scales were measured...... by utilizing the atomic force microscope (AFM). The chemistry of the surfaces and the probe was varied between hydrophilic silica and hydrophobized silica. For hydrophilic silica surfaces, the friction coefficient was significantly higher for the particle coated surfaces than on the flat reference surface. All...

  12. Biofilm retention on surfaces with variable roughness and hydrophobicity.

    Science.gov (United States)

    Tang, Lone; Pillai, Saju; Revsbech, Niels Peter; Schramm, Andreas; Bischoff, Claus; Meyer, Rikke Louise

    2011-01-01

    Biofilms on food processing equipment cause food spoilage and pose a hazard to consumers. The bacterial community on steel surfaces in a butcher's shop was characterized, and bacteria representative of this community enriched from minced pork were used to study biofilm retention. Stainless steel (SS) was compared to two novel nanostructured sol-gel coatings with differing hydrophobicity. Surfaces were characterized with respect to roughness, hydrophobicity, protein adsorption, biofilm retention, and community composition of the retained bacteria. Fewer bacteria were retained on the sol-gel coated surfaces compared to the rougher SS. However, the two sol-gel coatings did not differ in either protein adsorption, biofilm retention, or microbial community composition. When polished to a roughness similar to sol-gel, the SS was colonized by the same amount of bacteria as the sol-gel, but the bacterial community contained fewer Pseudomonas cells. In conclusion, biofilm retention was affected more by surface roughness than chemical composition under the condition described in this study.

  13. Forces and friction between hydrophilic and hydrophobic surfaces: influence of oleate species.

    Science.gov (United States)

    Theander, Katarina; Pugh, Robert J; Rutland, Mark W

    2007-09-15

    The atomic force microscope has been used to investigate normal surface forces and lateral friction forces at different concentrations of sodium oleate, a frequently used fatty acid in the deinking process. The measurements have been performed using the colloidal probe technique with bead materials consisting of cellulose and silica. Cellulose was used together with a printing ink alkyd resin and mica, whereas silica was used with a hydrophobized silica wafer. The cellulose-alkyd resin system showed stronger double layer repulsion and the friction was reduced with increasing surfactant concentration. The adhesive interaction disappeared immediately on addition of sodium oleate. The normal surface forces for cellulose-mica indicated no apparent adsorption of the sodium oleate however, the friction coefficient increased on addition of sodium oleate, which we ascribe to some limited adsorption increasing the effective surface roughness. The silica-hydrophobic silica system showed a completely different surface force behavior at the different concentrations. An attractive hydrophobic interaction was evident since the surfaces jumped into adhesive contact at a longer distance than the van der Waals forces would predict. The strong adhesion was reflected in the friction forces as a nonlinear relationship between load and friction and a large friction response at zero applied load. Indirect evidence of adsorption to the hydrophilic silica surface was also observed in this case, and QCM studies were performed to confirm the adsorption of material to both surfaces.

  14. Ions-induced nanostructuration: effect of specific ionic adsorption on hydrophobic polymer surfaces.

    Science.gov (United States)

    Siretanu, Igor; Chapel, Jean-Paul; Bastos-González, Delfi; Drummond, Carlos

    2013-06-06

    The effect of surface charges on the ionic distribution in close proximity to an interface has been extensively studied. On the contrary, the influence of ions (from dissolved salts) on deformable interfaces has been barely investigated. Ions can adsorb from aqueous solutions on hydrophobic surfaces, generating forces that can induce long-lasting deformation of glassy polymer films, a process called ion-induced polymer nanostructuration, IPN. We have found that this process is ion-specific; larger surface modifications are observed in the presence of water ions and hydrophobic and amphiphilic ions. Surface structuration is also observed in the presence of certain salts of lithium. We have used streaming potential and atomic force microscopy to study the effect of dissolved ions on the surface properties of polystyrene films, finding a good correlation between ionic adsorption and IPN. Our results also suggest that the presence of strongly hydrated lithium promotes the interaction of anions with polystyrene surfaces and more generally with hydrophobic polymer surfaces, triggering then the IPN process.

  15. Viscous boundary lubrication of hydrophobic surfaces by mucin.

    Science.gov (United States)

    Yakubov, Gleb E; McColl, James; Bongaerts, Jeroen H H; Ramsden, Jeremy J

    2009-02-17

    The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin "Orthana" (Mw=0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces. The presence of mucin also results in a shift of the mixed lubrication regime to lower entrainment speeds. The observed boundary lubrication behavior of mucin was found to depend on the bulk concentration, and we linked this to the structure and dynamics of the adsorbed mucin films, which are assessed using optical waveguide light spectroscopy. We observe a composite structure of the adsorbed mucin layer, with its internal structure governed by entanglement. The film thickness of this adsorbed layer increases with concentration, while the boundary friction coefficient for rough surfaces was found to be inversely proportional to the thickness of the adsorbed film. This link between lubrication and structure of the film is consistent with a viscous boundary lubrication mechanism, i.e., a thicker adsorbed film, at a given sliding speed, results in a lower local shear rate and, hence, in a lower local shear stress. The estimated local viscosities of the adsorbed layer, derived from the friction measurements and the polymer layer density, are in agreement with each other.

  16. Effect of hydrophobic microstructured surfaces on conductive ink printing

    International Nuclear Information System (INIS)

    Kim, Seunghwan; Kang, Hyun Wook; Lee, Kyung Heon; Sung, Hyung Jin

    2011-01-01

    Conductive ink was printed on various microstructured substrates to measure the printing quality. Poly-dimethylsiloxane (PDMS) substrates were used to test the printability of the hydrophobic surface material. Microstructured arrays of 10 µm regular PDMS cubes were prepared using the MEMS fabrication technique. The gap distance between the cubes was varied from 10 to 40 µm. The printing wettability of the microstructured surfaces was determined by measuring the contact angle of a droplet of silver conductive ink. Screen-printing methods were used in the conductive line printing experiment. Test line patterns with finely varying widths (30–250 µm) were printed repeatedly, and the conductivity of the printed lines was measured. The printability, which was defined as the ratio of the successfully printed patterns to the total number of printed patterns, was analyzed as a function of the linewidth and the gap distance of the microstructured surfaces

  17. LapF and Its Regulation by Fis Affect the Cell Surface Hydrophobicity of Pseudomonas putida.

    Science.gov (United States)

    Lahesaare, Andrio; Ainelo, Hanna; Teppo, Annika; Kivisaar, Maia; Heipieper, Hermann J; Teras, Riho

    2016-01-01

    The ability of bacteria to regulate cell surface hydrophobicity is important for the adaptation to different environmental conditions. The hydrophobicity of cell surface can be determined by several factors, including outer membrane and surface proteins. In this study, we report that an adhesin LapF influences cell surface hydrophobicity of Pseudomonas putida. Cells lacking LapF are less hydrophobic than wild-type cells in stationary growth phase. Moreover, the overexpression of the global regulator Fis decreases surface hydrophobicity by repressing the expression of lapF. Flow cytometry analysis revealed that bacteria producing LapF are more viable when confronted with methanol (a hydrophilic compound) but are more susceptible to 1-octanol (a hydrophobic compound). Thus, these results revealed that LapF is the hydrophobicity factor for the cell surface of P. putida.

  18. Studies on polyurethane adhesives and surface modification of hydrophobic substrates

    Science.gov (United States)

    Krishnamoorthy, Jayaraman

    studies involved making functionalized, thickness-controlled, wettability-controlled multilayers on hydrophobic substrates and the adsorption of carboxylic acid-terminated poly(styrene-b-isoprene) on alumina/silica substrates. Poly(vinyl alcohol) has been shown to adsorb onto hydrophobic surfaces irreversibly due to hydrophobic interactions. This thin semicrystalline coating is chemically modified using acid chlorides, butyl isocyanate and butanal to form thicker and hydrophobic coatings. The products of the modification reactions allow adsorption of a subsequent layer of poly(vinyl alcohol) that could subsequently be hydrophobized. This 2-step (adsorption/chemical modification) allows layer-by-layer deposition to prepare coatings with thickness, chemical structure and wettability control on any hydrophobic surface. Research on adsorption characteristics of carboxylic acid-terminated poly(styrene-b-isoprene) involved syntheses of block copolymers with the functional group present at specific ends. Comparative adsorption studies for carboxylic acid-terminated and hydrogen-terminated block copolymers was carried out on alumina and silica substrates.

  19. Reduction of surface hydrophobicity using a stimulus-responsive polysaccharide.

    Science.gov (United States)

    Sedeva, Iliana G; Fornasiero, Daniel; Ralston, John; Beattie, David A

    2010-10-19

    The adsorption of carboxymethyl cellulose (CMC) onto a hydrophobic self-assembled monolayer has been characterized using the quartz crystal microbalance (with dissipation monitoring, QCM-D). Adsorption was studied as a function of initial solution conditions. CMC adsorbs to a greater extent at high ionic strength (10(-1) M KCl as opposed to 10(-2) M KCl) or low pH (3 as opposed to 9). The solution conditions that yielded the lowest initial adsorbed amount (10(-2) M KCl, pH 9) were used as a reference to investigate the response of the adsorbed layer to a switch in solution conditions after adsorption (i.e., to higher ionic strength (10(-1) M KCl) or lower pH (pH 3)). The adsorbed layer released significant amounts of hydration water after each solution switch, as determined by the QCM-D measurements. This expulsion of hydration water was fully reversible. For the two solution switches, reducing the solution pH resulted in a more pronounced change in the amount of hydration water within the adsorbed CMC, accompanied by a distinct conformational change, as determined from a QCM D-f plot. In addition to studying adsorption using QCM-D, the effect of adsorbed CMC on surface hydrophobicity has been investigated using captive bubble contact angle measurements. The effect of the polymer on the contact angle of the surface was seen to be greatest when adsorbed at low pH or at higher ionic strength. CMC was also seen to have a significantly enhanced ability to reduce the surface hydrophobicity after both the ionic strength and pH switches, lowering the advancing water contact angle by 6 and 23° and the receding water contact angle by 10 and 40° for the ionic strength and pH switches, respectively. As with the change in hydration water content, the change in the contact angle of the polymer-coated surface following the solution switches was reversible.

  20. Control and characterization of textured, hydrophobic ionomer surfaces

    Science.gov (United States)

    Wang, Xueyuan

    Polymer thin films are of increasing interest in many industrial and technological applications. Superhydrophobic, self-cleaning surfaces have attracted a lot of attention for their application in self-cleaning, anti-sticking coatings, stain resistance, or anti-contamination surfaces in diverse technologies, including medical, transportation, textiles, electronics and paints. This thesis focuses on the preparation of nanometer to micrometer-size particle textured surfaces which are desirable for super water repellency. Textured surfaces consisting of nanometer to micrometer-sized lightly sulfonated polystyrene ionomer (SPS) particles were prepared by rapid evaporation of the solvent from a dilute polymer solution cast onto silica. The effect of the solvent used to spin coat the film, the molecular weight of the ionomer, and the rate of solvent evaporation were investigated. The nano-particle or micron-particle textured ionomer surfaces were prepared by either spin coating or solution casting ionomer solutions at controlled evaporation rates. The surface morphologies were consistent with a spinodal decomposition mechanism where the surface first existed as a percolated-like structure and then ripened into droplets if molecular mobility was retained for sufficient time. The SPS particles or particle aggregates were robust and resisted deformation even after annealing at 120°C for one week. The water contact angles on as-prepared surfaces were relatively low, ~ 90° since the polar groups in ionomer reduce the surface hydrophobicity. After chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltrichlorosilane, the surface contact angles increased to ~ 109° on smooth surfaces and ~140° on the textured surfaces. Water droplets stuck to these surfaces even when tilted 90 degrees. Superhydrophobic surfaces were prepared by spraying coating ionomer solutions and Chemical Vapor Deposition (CVD) of 1H,1H,2H,2H-perfluorooctyltrichlorosilane onto textured surfaces. The

  1. EWOD driven cleaning of bioparticles on hydrophobic and superhydrophobic surfaces.

    Science.gov (United States)

    Jönsson-Niedziółka, M; Lapierre, F; Coffinier, Y; Parry, S J; Zoueshtiagh, F; Foat, T; Thomy, V; Boukherroub, R

    2011-02-07

    Environmental air monitoring is of great interest due to the large number of people concerned and exposed to different possible risks. From the most common particles in our environment (e.g. by-products of combustion or pollens) to more specific and dangerous agents (e.g. pathogenic micro-organisms), there are a large range of particles that need to be controlled. In this article we propose an original study on the collection of electrostatically deposited particles using electrowetting droplet displacement. A variety of particles were studied, from synthetic particles (e.g. Polystyrene Latex (PSL) microsphere) to different classes of biological particle (proteins, bacterial spores and a viral simulant). Furthermore, we have compared ElectroWetting-On-Dielectric (EWOD) collecting efficiency using either a hydrophobic or a superhydrophobic counter electrode. We observe different cleaning efficiencies, depending on the hydrophobicity of the substrate (varying from 45% to 99%). Superhydrophobic surfaces show the best cleaning efficiency with water droplets for all investigated particles (MS2 bacteriophage, BG (Bacillus atrophaeus) spores, OA (ovalbumin) proteins, and PSL).

  2. Velocity profiles of fluid flow close to a hydrophobic surface

    Science.gov (United States)

    Fialová, Simona; Pochylý, František; Kotek, Michal; Jašíková, Darina

    The results of research on viscous liquid flow upon a superhydrophobic surface are presented in the paper. In the introduction, the degrees of surface hydrophobicity in correlation with an adhesion coefficient are defined. The usage of the adhesion coefficient for the definition of a new boundary condition is employed for expressing the slip of the liquid over the superhydrophobic surface. The slip of the liquid was identified on a special experimental device. The essence of the device consists of a tunnel of rectangular cross section whose one wall is treated with a superhydrophobic layer. The other walls are made of transparent organic glass whose surface is hydrophilic. Velocity profiles are measured by PIV. The methodology is drawn so that it allows the speed determination at the closest point to the wall. The measurements were performed for different Reynolds numbers for both laminar and turbulent flow. Based on the measured velocity profiles, marginal terms of use have been verified, expressing slippage of the liquid on the wall. New forms of velocity profiles considering superhydrophobic surfaces are shown within the work.

  3. Transforming plastic surfaces with electrophilic backbones from hydrophobic to hydrophilic.

    Science.gov (United States)

    Kim, Samuel; Bowen, Raffick A R; Zare, Richard N

    2015-01-28

    We demonstrate a simple nonaqueous reaction scheme for transforming the surface of plastics from hydrophobic to hydrophilic. The chemical modification is achieved by base-catalyzed trans-esterification with polyols. It is permanent, does not release contaminants, and causes no optical or mechanical distortion of the plastic. We present contact angle measurements to show successful modification of several types of plastics including poly(ethylene terephthalate) (PET) and polycarbonate (PC). Its applicability to blood analysis is explored using chemically modified PET blood collection tubes and found to be quite satisfactory. We expect this approach will reduce the cost of manufacturing plastic devices with optimized wettability and can be generalized to other types of plastic materials having an electrophilic linkage as its backbone.

  4. Structure of aqueous electrolyte solutions near a hydrophobic surface

    Directory of Open Access Journals (Sweden)

    M.Kinoshita

    2007-09-01

    Full Text Available The structure of aqueous solutions of 1:1 salts (KCl, NaCl, KF,and CsI near a hydrophobic surface is analysed using the angle-dependent integral equation theory. Water molecules are taken to be hard spheres imbedded with multipolar moments including terms up to octupole order, and hard spherical ions are immersed in this model water. The many-body interactions associated with molecular polarizability are treated at the self-consistent mean field level. The effects of cationic and anionic sizes and salt concentration in the bulk are discussed in detail. As the salt concentration increases, the layer of water molecules next to the surface becomes denser but its orientational order remains almost unchanged. The concentration of each ion at the surface can be drastically different from that in the bulk. Asa striking example, at sufficiently low salt concentrations, the concentration of I- is about 500 times higher than that of F- at the surface.

  5. Engineering Extreme Hydrophobic and Super Slippery Water Shedding Surfaces

    Science.gov (United States)

    McHale, Glen

    2017-04-01

    The intrinsic water repellency of a material is fundamentally determined by its surface chemistry, but alone this does not determine the ability of a surface to shed water. Physical factors such as the surface texture/topography, rigidity/flexibility, granularity/porosity combined with the intrinsic wetting properties of the liquid with the surface and whether it is infused by a lubricating liquid are equally important. In this talk I will outline fundamental, but simple, ideas on the topographic enhancement of surface chemistry to create superhydrophobicity, the adhesion of particles to liquid-air interfaces to create liquid marbles, elastocapillarity to create droplet wrapping, and lubricant impregnated surfaces to create completely mobile droplets [1-3]. I will discuss how these ideas have their origins in natural systems and surfaces, such as Lotus leaves, galling aphids and the Nepenthes pitcher plant. I will show how we have applied these concepts to study the wetting of granular systems, such as sand, to understand extreme soil water repellency. I will argue that relaxing the assumption that a solid substrate is fixed in shape and arrangement, can lead to the formation of liquid marbles, whereby a droplet self-coats in a hydrophobic powder/grains. I will show that the concepts of wetting and porosity blur as liquids penetrate into a porous or granular substrate. I will also discuss how lubricant impregnated super slippery surfaces can be used to study a pure constant contact angle mode of droplet evaporation [4]. Finally, I will show dewetting of a surface is not simply a video reversal of wetting [5], and I will give an example of the use of perfect hydrophobicity using the Leidenfrost effect to create a new type of low friction mechanical and hear engine [6]. References: [1] Shirtcliffe, N. J., et al., An introduction to superhydrophobicity. Advances in Colloid and Interface Science, vol. 161, pp.124-138 (2010). [2] McHale, G. & Newton, M. I. Liquid

  6. Fabricating Super-hydrophobic Polydimethylsiloxane Surfaces by a Simple Filler-Dissolved Process

    Science.gov (United States)

    Lin, Yung-Tsan; Chou, Jung-Hua

    2010-12-01

    The self-cleaning effect of super-hydrophobic surfaces has attracted the attention of researchers. Typical ways of manufacturing super-hydrophobic surfaces include the use of either dedicated equipment or a complex chemical process. In this study, a simple innovative filler-dissolved method is developed using mainly powder salt and rinsing to form hydrophobic surfaces. This method can produce large super-hydrophobic surfaces with porous and micro rib surface structures. It can also be applied to curved surfaces, including flexible membranes. The contact angle of the manufactured artificial hydrophobic surface is about 160°. Furthermore, water droplets roll off the surface readily at a sliding angle of less than 5°, resembling the nonwetting lotus like effect.

  7. Prediction of protein retention times in hydrophobic interaction chromatography by robust statistical characterization of their atomic-level surface properties.

    NARCIS (Netherlands)

    Hanke, A.T.; Klijn, M.E.; Verhaert, P.D.; Wielen, van der L.; Ottens, M.; Eppink, M.H.M.; Sandt, van de E.J.A.X.

    2016-01-01

    The correlation between the dimensionless retention times (DRT) of proteins in hydrophobic interaction chromatography (HIC) and their surface properties were investigated. A ternary atomic-level hydrophobicity scale was used to calculate the distribution of local average hydrophobicity across the

  8. Effects of surface hydrophobicity on the conformational changes of polypeptides of different length.

    Science.gov (United States)

    Mu, Yan

    2011-09-01

    We studied the effects of surface hydrophobicity on the conformational changes of different length polypeptides by calculating the free energy difference between peptide structures using the bias-potential Monte Carlo technique and the probability ratio method. It was found that the hydrophobic surface plays an important role in the stability of secondary structures of the polypeptides with hydrophobic side chains. For short GAAAAG peptides, the hydrophobic surface destabilizes the α helix but stabilizes the β hairpin in the entire temperature region considered in our study. Interestingly, when the surface hydrophobic strength ε(hpsf)≥ε(hp), the most stable structure in the low temperature region changes from α helix to β hairpin, and the corresponding phase transition temperature increases slightly. For longer GAAAAAAAAAAG peptides, the effects of the relatively weak hydrophobic surface (ε(hpsf) ε(hp)) may further disturb the formation of both α-helical and β structures. Moreover, the phase transition temperature between α-helical structures and random coils significantly decreases due to the helicity loss when ε(hpsf)>ε(hp). Our findings provide a basic and quantitative picture for understanding the effects of a hydrophobic surface on the conformational changes of the polypeptides with hydrophobic side chains. From an application viewpoint, the present study is helpful in developing alternative strategies of producing high-quality biological fibrillar materials and functional nanoscale devices by the self-assembly of the polypeptides on hydrophobic surfaces.

  9. INVESTIGATION OF MICRO AND NANOSTRUCTURE OF HYDROPHOBIC PLANTS SURFACE

    Directory of Open Access Journals (Sweden)

    M. V. Zhukov

    2014-03-01

    Full Text Available Micro and nanostructure of petals and flowers of pink rose family having super hydrophobic phenomenon known as "lotus effect" was studied by optical and scanning probe microscopy. Quasi-ordered corrugated structure was found on the surface of the rose petals. It represents the ensemble of smoothed shape peaks like a lotus leaf structure. Structure saving during dehydration of rose petal (for 5 days by drying in the air under normal conditions was found, the difference is apparent in the density of the arrangement and shape of the peaks, which in case of dehydrated rose petal have a smoother shape. Thus, the typical distance between the structure peaks of the native rose petal was 25-30 mkm, average peak height was 8 mkm, the peak width at half- height was about 15 mkm, peak top approximated by a sphere had a radius of about 2-3 mkm, the slope angle of the surface tangent to the peak axis was about 38-42º. Characteristic distance between the peaks for a dried rose petal is reduced to 20-25 mkm, the average peak height was 8 mkm, the width of the peak at half - height was about 18 mkm, peak top approximated by a sphere had a radius of about 5-6 mkm, the slope angle of the surface tangent to the peak axis was about 40-50º. A thin nanostructure of separate peak was examined on a dried petal, which consists of longitudinal bands of about 150-300 nm in height and about 2-3 mkm in width. While visualizing of rose stem leaves, a cellular structure with micro-pores and nanometer canals on the surface was discovered. The analysis of surface roughness on different parts of investigated objects was held. A single peak roughness was about 650 nm for a living rose petal, 300 nm for dried rose petal, roughness of the rose stem leaf was about 65-70 nm with sizes of scanned areas equal to 10x10 mkm. Studies were conducted on the integrated optical module Optem of Ntegra Aura microscope (NT-MDT, Russia and on the scanning probe microscope NanoEducator LE (NT

  10. Evaluation of Relative Yeast Cell Surface Hydrophobicity Measured by Flow Cytometry

    Directory of Open Access Journals (Sweden)

    Lisa Colling

    2005-01-01

    Full Text Available Objective: To develop an efficient method for evaluating cell surface hydrophobicity and to apply the method to demonstrate the effects of fungal growth conditions on cell surface properties.

  11. An experimental investigation of evaporating sessile droplet on super-hydrophobic surface

    International Nuclear Information System (INIS)

    Shin, Dong Hwan; Lee, Seong Hyuk; Yoo, Jung Yul

    2008-01-01

    The objective of this study is to investigate the evaporation process of a water droplet on hydrophobic and hydrophilic surfaces. Time-dependent contact angle, height, radius, surface area, and volume were measured for three different surfaces, such as glass, OctadecylTrichloroSilane(OTS), and AlkylKetene Dimmer(AKD) using a digital image analysis technique. For hydrophilic surfaces, the measured contact angle, liquid volume, and height are also compared with numerical estimation. It is found that for super-hydrophobic surfaces, the contact line becomes no longer pinned during evaporation, and three distinct stages for hydrophobic surface cannot be found. For the super-hydrophobic surface, it takes the longest time for evaporation because the droplet maintains spherical shape even near the end of evaporation process

  12. Hydrophobic and superhydrophobic surfaces fabricated using atmospheric pressure cold plasma technology: A review.

    Science.gov (United States)

    Dimitrakellis, Panagiotis; Gogolides, Evangelos

    2018-03-29

    Hydrophobic surfaces are often used to reduce wetting of surfaces by water. In particular, superhydrophobic surfaces are highly desired for several applications due to their exceptional properties such as self-cleaning, anti-icing, anti-friction and others. Such surfaces can be prepared via numerous methods including plasma technology, a dry technique with low environmental impact. Atmospheric pressure plasma (APP) has recently attracted significant attention as lower-cost alternative to low-pressure plasmas, and as a candidate for continuous rather than batch processing. Although there are many reviews on water-repellent surfaces, and a few reviews on APP technology, there are hardly any review works on APP processing for hydrophobic and superhydrohobic surface fabrication, a topic of high importance in nanotechnology and interface science. Herein, we critically review the advances on hydrophobic and superhydrophobic surface fabrication using APP technology, trying also to give some perspectives in the field. After a short introduction to superhydrophobicity of nanostructured surfaces and to APPs we focus this review on three different aspects: (1) The atmospheric plasma reactor technology used for fabrication of (super)hydrophobic surfaces. (2) The APP process for hydrophobic surface preparation. The hydrophobic surface preparation processes are categorized methodologically as: a) activation, b) grafting, c) polymerization, d) roughening and hydrophobization. Each category includes subcategories related to different precursors used. (3) One of the most important sections of this review concerns superhydrophobic surfaces fabricated using APP. These are methodologically characterized as follows: a) single step processes where micro-nano textured topography and low surface energy coating are created at the same time, or b) multiple step processes, where these steps occur sequentially in or out of the plasma. We end the review with some perspectives in the field. We

  13. Influence of cosolvents on the hydrophobic surface immobilization topography of Candida antarctica lipase B

    Science.gov (United States)

    The presence of cosolvents and co-solutes during the immobilization of lipases on hydrophobic supports may influence the extent of lipase immobilization and the long-term catalytic stability of the biocatalyst. Candida antarctica B lipase immobilization was examined on a hydrophobic surface, i.e., ...

  14. Fabrication of TiO2/EP super-hydrophobic thin film on filter paper surface.

    Science.gov (United States)

    Gao, Zhengxin; Zhai, Xianglin; Liu, Feng; Zhang, Ming; Zang, Deli; Wang, Chengyu

    2015-09-05

    A composite filter paper with super-hydrophobicity was obtained by adhering micro/nano structure of amorphous titanium dioxide on the filter paper surface with modifying low surface energy material. By virtue of the coupling agent, which plays an important part in bonding amorphous titanium dioxide and epoxy resin, the structure of super-hydrophobic thin film on the filter paper surface is extremely stable. The microstructure of super-hydrophobic filter paper was characterized by scanning electron microscopy (SEM), the images showed that the as-prepared filter paper was covered with uniform amorphous titanium dioxide particles, generating a roughness structure on the filter paper surface. The super-hydrophobic performance of the filter paper was characterized by water contact angle measurements. The observations showed that the wettability of filter paper samples transformed from super-hydrophilicity to super-hydrophobicity with the water contact angle of 153 ± 1°. Some experiments were also designed to test the effect of water-oil separation and UV-resistant by the super-hydrophobic filter paper. The prepared super-hydrophobic filter paper worked efficiently and simply in water-oil separation as well as enduringly in anti-UV property after the experiments. This method offers an opportunity to the practical applications of the super-hydrophobic filter paper. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, N.P.; Norde, W.; Meil, H.C.; Busscher, H.J.

    2008-01-01

    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F-prev) and to detach adhering bacteria (F-det) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  16. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, Niels P.; Norde, Willem; van der Mei, Henny C.; Busscher, Henk J.

    2008-01-01

    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F(prev)) and to detach adhering bacteria (F(det)) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  17. Super-hydrophobic surfaces from a simple coating method: a bionic nanoengineering approach

    International Nuclear Information System (INIS)

    Liu Yuyang; Chen Xianqiong; Xin, J H

    2006-01-01

    Inspired by the self-cleaning behaviour of lotus leaves in nature, we developed a simple coating method that can facilitate the bionic creation of super-hydrophobic surfaces on various substrates, thus providing a feasible way of fabricating super-hydrophobic surfaces for civil and industrial applications. Micro-nanoscale binary structured composite particles of silica/fluoropolymer were prepared using an emulsion-mediated sol-gel process, and then these composite particles were applied to various substrates to mimic the surface microstructures of lotus leaves. Super-hydrophobic surfaces with a water contact angle larger than 150 deg. are obtained, and these super-hydrophobic surfaces are expected to have potential applications for rusting-resistant, anti-fog and self-cleaning treatments

  18. Droplets on porous hydrophobic surfaces perfused with gas: An air-table for droplets

    Science.gov (United States)

    Vourdas, Nikolaos; Stathopoulos, Vassilis; Laboratory of Chemistry; Materials Technology Team

    2016-11-01

    Wetting phenomena on porous hydrophobic surfaces are strongly related to the volume and the pressure of gas pockets resided at the solid-liquid interface. When the porous medium is perfused with gas by means of backpressure an inherently sessile pinned droplet undergoes various changes in its shape, contact angles and mobility. This provides an alternative method for active and controlled droplet actuation, without use of electricity, magnetism, foreign particles etc. Superhydrophobicity is not a prerequisite, electrode fabrication is not needed, the liquid is not affected thermally or chemically etc. In this work we explore this method, study the pertinent underlying mechanisms, and propose some applications. The adequate backpressure for droplet actuation has been measured for various hydrophobic porous surfaces. Backpressure for actuation may be as low as some tens of mbar for some cases, thus providing a rather low-energy demanding alternative. The droplet actuation mechanism has been followed numerically; it entails depinning of the receding contact line and movement, by means of a forward wave propagation reaching on the front of the droplet. Applications in valving water plugs inside open- or closed- channel fluidics will be provided.

  19. Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Ping; Zhang, Kan; Du, Suxuan [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Meng, Qingnan [College of Construction Engineering, Jilin University, Changchun, 130026 (China); He, Xin [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Wang, Shuo [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Wen, Mao, E-mail: wenmao225@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Zheng, Weitao, E-mail: WTZheng@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China)

    2017-06-15

    Highlights: • Intrinsically hydrophilic NbN films can transfer to hydrophobic Nb-Ag-N films by doping Ag atoms into NbN sublattice. • Solute Ag can promote that the hydrophobic Ag{sub 2}O groups formed on the Nb-Ag-N film surface through self-oxidation. • The present work may provide a straightforward approach for the production of robust hydrophobic ceramic surfaces. - Abstract: Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag{sub 2}O groups on the films surfaces through self-oxidation, because Ag cations (Ag{sup +}) in Ag{sub 2}O are the filled-shell (4d{sup 10}5S{sup 0}) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag{sub 2}O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

  20. Ultimate Cavity Dynamics of Hydrophobic Spheres Impacting on Free Water Surfaces

    KAUST Repository

    Mansoor, Mohammad M.

    2012-12-01

    Cavity formation resulting from the water-entry of solid objects has been the subject of extensive research owing to its practical relevance in naval, military, industrial, sports and biological applications. The cavity formed by an impacting hydrophobic sphere normally seals at two places, one below (deep seal) and the other above the water surface (surface seal). For Froude numbers , the air flow into the resulting cavity is strong enough to suck the splash crown above the surface and disrupt the cavity dynamics before it deep seals. In this research work we eliminate surface seals by means of a novel practice of using cone splash-guards and examine the undisturbed transient cavity dynamics by impact of hydrophobic spheres for Froude numbers ranging . This enabled the measurement of extremely accurate pinch-off heights, pinch-off times, radial cavity collapse rates, and jet speeds in an extended range of Froude numbers compared to the previous work of Duclaux et al. (2007). Results in the extended regime were in remarkable agreement with the theoretical prediction of scaled pinch-off depth, and experimentally derived pinch-off time for . Furthermore, we investigated the influence of confinement on cavity formation by varying the cross-sectional area of the tank of liquid. In conjunction with surface seal elimination we observed the formation of multiple pinch-off points where a maximum of four deep seals were obtained in a sequential order for the Froude number range investigated. The presence of an elongated cavity beneath the first pinch-off point 5 resulted in evident "kinks" primarily related to the greatly diminished air pressure at the necking region caused by supersonic air flows (Gekle et al. 2010). Such flows passing through second pinch-offs were also found to choke the cavities beneath the first pinch- off depths causing radial expansion and hence disappearance of downward jets.

  1. Water in contact with extended hydrophobic surfaces: Direct evidence of weak dewetting

    DEFF Research Database (Denmark)

    Jensen, Torben René; Jensen, Morten Østergaard; Reitzel, Niels

    2003-01-01

    X-ray reflectivity measurements reveal a significant dewetting of a large hydrophobic paraffin surface floating on water. The dewetting phenomenon extends less than 15 Angstrom into the bulk water phase and results in an integrated density deficit of about one water molecule per 25-30 Angstrom(2......) of water in contact with the paraffin surface. The results are supported by molecular dynamics simulations and related to the hydrophobic effect....

  2. Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

    International Nuclear Information System (INIS)

    Fang Zhi; Qiu Yuchang; Wang Hui; Kuffel, E

    2007-01-01

    Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment. The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CH 3 and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly

  3. Control of hydrophobic surface and wetting states in ultra-flat ZnO films by GLAD method

    Science.gov (United States)

    Chi, Po-Wei; Su, Chih-Wei; Wei, Da-Hua

    2017-05-01

    Ultra-flat Zinc oxide (ZnO) films with natural hydrophobicity were sputtered onto glass substrates by glancing angle deposition (GLAD) method without addition of active oxygen at room temperature under different glancing angles relating to the sample holder. The sample holder was positioned at glancing angles of 0° and 30°, and the sputtering power was fixed at 75 W with low argon (Ar) pressure of 1 × 10-2 Torr during deposition process. According to analysis of surface composition and structure, the naturally hydrophobic wetting state can be attributed to the different grain structure and hydrocarbon adsorbates on the top of the film surface. On the other hand, the interfacial water molecules near the surface of ultra-flat ZnO films are confirmed belong to the hydrophobic hydrogen structure by Fourier transform infrared/attenuated total reflection. In addition, the water contact angle was significantly improved by a simple factor of glancing angle. The water contact angle value of ultra-flat ZnO films increased from 90° to 98° while the sample holder is with glancing angle of 30°. Moreover, our present ultra-flat ZnO films also exhibited excellent transparency over 80%, and the surface wetting switched from hydrophobic to hydrophilic states after exposing in ultraviolet (UV) surroundings. Then, the ZnO films could be freely and stably reversed back to hydrophobicity after stored in dark surroundings. This present study not only demonstrates that the natural wettability of ultra-flat ZnO films is strongly associated with surface composition and structure, but also provides an easy way to modulate and improve the surface wettability. This also extends the potential applications of ultra-flat ZnO thin films and aids a profound understanding for device design and material development.

  4. Surface hydrophobicity of slippery zones in the pitchers of two Nepenthes species and a hybrid

    Science.gov (United States)

    Wang, Lixin; Zhou, Qiang

    2016-01-01

    To investigate the hydrophobicity of slippery zones, static contact angle measurement and microstructure observation of slippery surfaces from two Nepenthes species and a hybrid were conducted. Marginally different static contact angles were observed, as the smallest (133.83°) and greatest (143.63°) values were recorded for the N. alata and N. miranda respectively, and the median value (140.40°) was presented for the N. khasiana. The slippery zones under investigation exhibited rather similar surface morphologies, but different structural dimensions. These findings probably suggest that the geometrical dimensions of surface architecture exert primary effects on differences in the hydrophobicity of the slippery zone. Based on the Wenzel and Cassie-Baxter equations, models were proposed to analyze the manner in which geometrical dimensions affect the hydrophobicity of the slippery surfaces. The results of our analysis demonstrated that the different structural dimensions of lunate cells and wax platelets make the slippery zones present different real area of the rough surface and thereby generate somewhat distinguishable hydrophobicity. The results support a supplementary interpretation of surface hydrophobicity in plant leaves, and provide a theoretical foundation for developing bioinspired materials with hydrophobic properties and self-cleaning abilities.

  5. Mapping Hydrophobicity on the Protein Molecular Surface at Atom-Level Resolution

    Science.gov (United States)

    Nicolau Jr., Dan V.; Paszek, Ewa; Fulga, Florin; Nicolau, Dan V.

    2014-01-01

    A precise representation of the spatial distribution of hydrophobicity, hydrophilicity and charges on the molecular surface of proteins is critical for the understanding of the interaction with small molecules and larger systems. The representation of hydrophobicity is rarely done at atom-level, as this property is generally assigned to residues. A new methodology for the derivation of atomic hydrophobicity from any amino acid-based hydrophobicity scale was used to derive 8 sets of atomic hydrophobicities, one of which was used to generate the molecular surfaces for 35 proteins with convex structures, 5 of which, i.e., lysozyme, ribonuclease, hemoglobin, albumin and IgG, have been analyzed in more detail. Sets of the molecular surfaces of the model proteins have been constructed using spherical probes with increasingly large radii, from 1.4 to 20 Å, followed by the quantification of (i) the surface hydrophobicity; (ii) their respective molecular surface areas, i.e., total, hydrophilic and hydrophobic area; and (iii) their relative densities, i.e., divided by the total molecular area; or specific densities, i.e., divided by property-specific area. Compared with the amino acid-based formalism, the atom-level description reveals molecular surfaces which (i) present an approximately two times more hydrophilic areas; with (ii) less extended, but between 2 to 5 times more intense hydrophilic patches; and (iii) 3 to 20 times more extended hydrophobic areas. The hydrophobic areas are also approximately 2 times more hydrophobicity-intense. This, more pronounced “leopard skin”-like, design of the protein molecular surface has been confirmed by comparing the results for a restricted set of homologous proteins, i.e., hemoglobins diverging by only one residue (Trp37). These results suggest that the representation of hydrophobicity on the protein molecular surfaces at atom-level resolution, coupled with the probing of the molecular surface at different geometric resolutions

  6. Control of surface wettability for inkjet printing by combining hydrophobic coating and plasma treatment

    International Nuclear Information System (INIS)

    Park, Heung Yeol; Kang, Byung Ju; Lee, Dohyung; Oh, Je Hoon

    2013-01-01

    We have obtained a wide range of surface wettabilities of PI substrate for inkjet printing by combining hydrophobic solution coating and O 2 or Ar plasma treatments. Experiments were conducted to investigate the variation in inkjet-printed dot diameters with different surface treatments. The change in chemical and physical characteristics of treated surfaces was evaluated using static contact angle measurements, field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Only hydrophobic coated surface produces the smallest dot diameter and the largest contact angle. Dot diameter increases and contact angle decreases as the plasma treatment time increases. Since the removal of hydrophobic layer from the surface occurs due to the etching effect of O 2 and Ar plasma during the plasma treatments, F/C ratio decreases with increasing the plasma treatment time. Surface roughness variations are also observed after plasma treatments. The ranges of printed dot sizes for O 2 and Ar plasma treatments are 38 μm–70 μm and 38 μm–92 μm, respectively. Ar plasma treatment shows a wider range of surface wettability because of higher removal rate of the hydrophobic layer. This combination of hydrophobic coating and plasma treatment can offer an effective way to obtain a wide range of surface wettabilities for high quality inkjet-printed patterns. - Highlights: • Hydrophobic coating and plasma treatments were used to control surface wettability. • Inkjet-printed dot diameters increase with O 2 or Ar plasma treatment time. • Contact angles of Ag ink agree well with the variation tendency of dot diameters. • The removal of hydrophobic layer occurs during the plasma treatments. • Ar plasma treatment shows a wider range of surface wettability than O 2 plasma

  7. Comparison of the Fouling Release Properties of Hydrophobic Fluorinated and Hydrophilic PEGylated Block Copolymer Surfaces

    International Nuclear Information System (INIS)

    Krishnan, S.; Wang, N.; Ober, C.; Finlay, J.; Callow, M.; Callow, J.; Hexemer, A.; Sohn, K.; Kramer, E.; Fischer, D.

    2006-01-01

    To understand the role of surface wettability in adhesion of cells, the attachment of two different marine algae was studied on hydrophobic and hydrophilic polymer surfaces. Adhesion of cells of the diatom Navicula and sporelings (young plants) of the green macroalga Ulva to an underwater surface is mainly by interactions between the surface and the adhesive exopolymers, which the cells secrete upon settlement and during subsequent colonization and growth. Two types of block copolymers, one with poly(ethylene glycol) side-chains and the other with liquid crystalline, fluorinated side-chains, were used to prepare the hydrophilic and hydrophobic surfaces, respectively. The formation of a liquid crystalline smectic phase in the latter inhibited molecular reorganization at the surface, which is generally an issue when a highly hydrophobic surface is in contact with water. The adhesion strength was assessed by the fraction of settled cells (Navicula) or biomass (Ulva) that detached from the surface in a water flow channel with a wall shear stress of 53 Pa. The two species exhibited opposite adhesion behavior on the same sets of surfaces. While Navicula cells released more easily from hydrophilic surfaces, Ulva sporelings showed higher removal from hydrophobic surfaces. This highlights the importance of differences in cell-surface interactions in determining the strength of adhesion of cells to substrates

  8. Ultra fast laser machined hydrophobic stainless ateel surface for drag reduction in laminar flows

    NARCIS (Netherlands)

    Jagdheesh, R.; Pathiraj, B.; Martin, A.G.; Del Cerro, D.A.; Lammertink, R.G.H.; Lohse, D.; Huis in 't Veld, A.J.; Römer, G.R.B.E.

    2010-01-01

    Hydrophobic surfaces have attracted much attention due to their potential in microfluidics, lab on chip devices and as functional surfaces for the automotive and aerospace industry. The combination of a dual scale roughness with an inherent low-surface-energy coating material is the pre-requisite

  9. Ultra fast laser machined hydrophobic stainless steel surface for drag reduction in laminar flows

    NARCIS (Netherlands)

    Radhakrishnan, J.; Pathiraj, B.; Gomez Marin, Alvaro; Arnaldo del Cerro, D.; Lammertink, Rob G.H.; Lohse, Detlef; Huis in 't Veld, Bert; Römer, Gerardus Richardus, Bernardus, Engelina

    2010-01-01

    Hydrophobic surfaces have attracted much attention due to their potential in microfluidics, lab on chip devices and as functional surfaces for the automotive and aerospace industry. The combination of a dual scale roughness with an inherent low-surface-energy coating material is the pre-requisite

  10. Non-invasive high throughput approach for protein hydrophobicity determination based on surface tension.

    Science.gov (United States)

    Amrhein, Sven; Bauer, Katharina Christin; Galm, Lara; Hubbuch, Jürgen

    2015-12-01

    The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species. © 2015 Wiley Periodicals, Inc.

  11. Hydrophobic and hydrophilic surface nano-modification of PET fabric by plasma process.

    Science.gov (United States)

    Paosawatyanyong, B; Kamlangkla, K; Hodak, S K

    2010-11-01

    Polyethylene terephthalate (PET) fabrics were treated by radio frequency inductively coupled plasma (RF-ICP) to modify their hydrophobic and hydrophilic properties. Types of gases which were SF6, O2, N2 and Ar, treatment time, pressure and RF power were varied systematically. The water droplet contact angle measurements showed that, treating with SF6 plasma would result in the increase of hydrophobicity of PET samples while treating with O2, N2 and Ar plasmas would yield hydrophilic properties. In both hydrophobic and hydrophilic cases, the surface morphology of PET fibers was roughened after exposed to plasma. Hence, it is not obvious that these surface roughness induced by plasma is sufficient to yield the increase in hydrophobicity by the well known lotus effect.

  12. Super-hydrophobic surface treatment as corrosion protection for aluminum in seawater

    Energy Technology Data Exchange (ETDEWEB)

    He Tian; Wang Yuanchao; Zhang Yijian; Lv Qun; Xu Tugen [College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China); Liu Tao [Institute of Ocean Materials and Engineering, Shanghai Maritime University, Shanghai 200135 (China)], E-mail: yys2003ouc@163.com

    2009-08-15

    'Underwater super-hydrophobic' surface applied in the corrosion protection was prepared by melting myristic acid (CH{sub 3}(CH{sub 2}){sub 12}COOH) adsorbed onto the anodized aluminum. The static contact angle for seawater on the surface was measured to be 154{sup o}. The surface structure and composition were then characterized by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDS) and atomic force microscope (AFM). The electrochemical measurements showed that the super-hydrophobic surface significantly improved the corrosion resistance of aluminum in sterile seawater. In addition, the mechanism of the underwater super-hydrophobic surface applied in the corrosion resistance was discussed using a schematic.

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

    Science.gov (United States)

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

    2016-11-01

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-01

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

  16. Fabrication and hydrophobic characteristics of micro / nanostructures on polydimethylsiloxane surface prepared by picosecond laser

    Science.gov (United States)

    Bin, Wang; Dong, Shiyun; Yan, Shixing; Gang, Xiao; Xie, Zhiwei

    2018-03-01

    Picosecond laser has ultrashort pulse width and ultrastrong peak power, which makes it widely used in the field of micro-nanoscale fabrication. polydimethylsiloxane (PDMS) is a typical silicone elastomer with good hydrophobicity. In order to further improve the hydrophobicity of PDMS, the picosecond laser was used to fabricate a grid-like microstructure on the surface of PDMS, and the relationship between hydrophobicity of PDMS with surface microstructure and laser processing parameters, such as processing times and cell spacing was studied. The results show that: compared with the unprocessed PDMS, the presence of surface microstructure significantly improved the hydrophobicity of PDMS. When the number of processing is constant, the hydrophobicity of PDMS decreases with the increase of cell spacing. However, when the cell spacing is fixed, the hydrophobicity of PDMS first increases and then decreases with the increase of processing times. In particular, when the times of laser processing is 6 and the cell spacing is 50μm, the contact angle of PDMS increased from 113° to 154°, which reached the level of superhydrophobic.

  17. Anticorrosive behaviour of lumefantrine hydrophobic layer on mild steel surface

    Directory of Open Access Journals (Sweden)

    Pavithra M. Krishnegowda

    2016-06-01

    Full Text Available The surface modification of mild steel was achieved by chemical treatment in lumefantrine (LF solution. The surface morphology and wettability of modified surface was analysed by 3D profilometer and contact angle goniometer. The corrosion inhibition performance of modified mild steel surface in 1.0 M HCl solution was investigated by potentiodynamic polarization and electrochemical impedance techniques.Electroche­mical measurements illustrate that the corrosion of mild steel in acidic chloride medium get substantially reduced by introducing LF film on its surface (94 % efficiency. Quantum chemical parameters were evaluated by ab initio method and they confer appropriate theoretical support to the experimental findings.

  18. Droplet nucleation on a well-defined hydrophilic-hydrophobic surface of 10 nm order resolution.

    Science.gov (United States)

    Yamada, Yutaka; Ikuta, Tatsuya; Nishiyama, Takashi; Takahashi, Koji; Takata, Yasuyuki

    2014-12-09

    Water condensation on a hybrid hydrophilic-hydrophobic surface was investigated to reveal nucleation mechanisms at the microscale. Focused ion beam (FIB) irradiation was used to change the wettability of the hydrophobic surface with 10 nm order spatial resolution. Condensation experiments were conducted using environmental scanning electron microscopy; droplets, with a minimum diameter of 800 nm, lined up on the FIB-irradiated hydrophilic lines. The heterogeneous nucleation theory was extended to consider the water molecules attracted to the hydrophilic area, thereby enabling explanation of the nucleation mechanism under unsaturated conditions. Our results showed that the effective surface coverage of the water molecules on the hydrophilic region was 0.1-1.1 at 0.0 °C and 560 Pa and was dependent on the width of the FIB-irradiated hydrophilic lines and hydrophobic area. The droplet nucleation mechanism unveiled in this work would enable the design of new surfaces with enhanced dropwise condensation heat transfer.

  19. Hydrophobic fractal surface from glycerol tripalmitate and the effects on C6 glioma cell growth.

    Science.gov (United States)

    Zhang, Shanshan; Chen, Xuerui; Yu, Jing; Hong, Biyuan; Lei, Qunfang; Fang, Wenjun

    2016-06-01

    To provide a biomimic environment for glial cell culture, glycerol tripalmitate (PPP) has been used as a raw material to prepare fractal surfaces with different degrees of hydrophobicity. The spontaneous formation of the hydrophobic fractal surfaces was monitored by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The surface morphologies were observed by a scanning electron microscope (SEM), and then the fractal dimension (FD) values of the surfaces were determined with the box-counting method. C6 glioma cells were cultured and compared on different hydrophobic PPP surfaces and poly-L-lysine (PLL)-coated surface. The cell numbers as a function of incubation time on different surfaces during the cell proliferation process were measured, and the cell morphologies were observed under a fluorescence microscope. Influences of hydrophobic fractal surfaces on the cell number and morphology were analyzed. The experimental results show that the cell proliferation rates decrease while the cell morphology complexities increase with the growth of the fractal dimensions of the PPP surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Hydrophobic cotton textile surfaces using an amphiphilic graphene oxide (GO) coating

    International Nuclear Information System (INIS)

    Tissera, Nadeeka D.; Wijesena, Ruchira N.; Perera, J. Rangana; Nalin de Silva, K.M.; Amaratunge, Gehan A.J.

    2015-01-01

    Graphical abstract: - Highlights: • Different GO dispersions were prepared by sonicating different amounts of GO in water. Degree of exfoliation of these GO sheets in water was analyzed using Atomic Force Microscopy (AFM). • AFM results obtained showed higher the GO concentration on water more the size of GO sheets and lesser the degree of exfoliation. • GO with different amounts was deposited on cotton fabric using simple dyeing method. • High GO loading on cotton increase the surface area coverage of the textile fibers with GO sheets. This led to less edge to mid area ratio of grafted GO sheets. • As contribution of mid area of GO increase on fiber surface cotton fabric becomes more hydrophobic. • Amphiphilic property of GO sheets was used to lower the surface energy of the cotton fibers leading to hydrophobic property. - Abstract: We report for the first time hydrophobic properties on cotton fabric successfully achieved by grafting graphene oxide on the fabric surface, using a dyeing method. Graphite oxide synthesized by oxidizing natural flake graphite employing improved Hummer's method showed an inter layer spacing of ∼1 nm from XRD. Synthesized graphite oxide was exfoliated in water using ultrasound energy to obtain graphene oxide (GO). AFM data obtained for the graphene oxide dispersed in an aqueous medium revealed a non-uniform size distribution. FTIR characterization of the synthesized GO sheets showed both hydrophilic and hydrophobic functional groups present on the nano sheets giving them an amphiphilic property. GO flakes of different sizes were successfully grafted on to a cotton fabric surface using a dip dry method. Loading different amounts of graphene oxide on the cotton fiber surface allowed the fabric to demonstrate different degrees of hydrophobicity. The highest observed water contact angle was at 143° with the highest loading of graphene oxide. The fabric surfaces grafted with GO also exhibits adhesive type hydrophobicity

  1. Salmonella Sofia differs from other poultry-associated Salmonella serovars with respect to cell surface hydrophobicity.

    Science.gov (United States)

    Chia, T W R; Fegan, N; McMeekin, T A; Dykes, G A

    2008-12-01

    Salmonella enterica is one of the most important foodborne pathogens. Salmonella enterica subsp. II 4,12:b:- (Salmonella Sofia) is commonly found in Australian poultry. It has been suggested that physicochemical properties such as surface charge and hydrophobicity may affect bacterial attachment to surfaces and their ability to persist in food systems. A possible link between hydrophobicity cell surface charge and persistence of Salmonella from the poultry system was examined. Hydrophobicity of Salmonella Sofia (n = 14), Salmonella Typhimurium (n = 6), Salmonella Infantis (n = 3), and Salmonella Virchow (n = 2) was assayed using hydrophobic interaction chromatography, bacterial adherence to hydrocarbons (BATH), using xylene or hexadecane, and the contact angle method (CAM). Cellular surface charge (CSC) of the isolates was determined using zeta potential measurements. The majority (12 of 14) of Salmonella Sofia isolates were found to be hydrophobic when assayed using BATH with xylene, except isolates S1635 and S1636, and the other serovars were found to be hydrophilic. Salmonella Sofia isolates were not significantly different (P > 0.05) from isolates of other serovars as measured by hydrophobic interaction, BATH with hexadecane, or the CAM. No significant differences (P > 0.05) in zeta potential measurements were observed between isolates. Principal component analysis using results from all four measures of hydrophobicity allowed clear differentiation between isolates of the serovar Salmonella Sofia (except S1635 and S1636) and those of other Salmonella serovars. Differences in physicochemical properties may be a contributing factor to the Salmonella Sofia serovar's ability to attach to surfaces and persist in a food system.

  2. Tuning the hydrophobicity of ZSM-5 zeolites by surface silanization using alkyltrichlorosilane

    Science.gov (United States)

    Han, Xiaolong; Wang, Lei; Li, Jiding; Zhan, Xia; Chen, Jian; Yang, Jichu

    2011-09-01

    ZSM-5 zeolites were modified with alkyltrichlorosilanes of various chain lengths (octyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane and hexadecyltrichlorosilane) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermal gravimetric analysis (TGA) and contact angle measurements (CA). The results showed that a closely packed and hydrophobic layer was presented at the particles surface and the surface wetting property varied from hydrophilic to hydrophobic, even to superhydrophobic. It was interesting to notice that the hydrophobic properties of modified ZSM-5 particles could be tuned by varying the chain length of chlorosilane and changing the pretreatment temperature before silanization. With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. However, with an increase in the pretreatment temperature, the hydrophobicity decreased. Moreover, the relationship between the wetting properties and thermal stability was also investigated, the results showed that the modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250 °C in air. These modified ZSM-5 particles may be utilized for many potential applications, such as membrane fillers, selective adsorbents, catalysts, chromatographic supports and so on.

  3. Conformation of bovine submaxillary mucin layers on hydrophobic surface as studied by biomolecular probes

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Madsen, Jan Busk; Lee, Seunghwan

    2015-01-01

    non-linear responses with increasing surface concentration. The results from this study support the conventional amphiphilic, triblock model of BSM in the adsorption onto hydrophobic surface from aqueous solution.The biomolecular probe-based approaches employed in this study, however, provided further...

  4. Durable hydrophobic coating composition for metallic surfaces and method for the preparation of the composition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiong

    2017-02-14

    A durable hydrophobic coating composition containing fluorinated silanes for metallic surfaces, such as stainless steel surfaces. The composition includes at least one fluorine-containing silane compound, at least one phosphorus-containing silane compound, and at least one hydrolysable compound. This coating is suitable for condenser tubes, among other applications, to promote dropwise condensation.

  5. Hydrophobic and Metallophobic Surfaces: Highly Stable Non-wetting Inorganic Surfaces Based on Lanthanum Phosphate Nanorods.

    Science.gov (United States)

    Sankar, Sasidharan; Nair, Balagopal N; Suzuki, Takehiro; Anilkumar, Gopinathan M; Padmanabhan, Moothetty; Hareesh, Unnikrishnan Nair S; Warrier, Krishna G

    2016-03-09

    Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications.

  6. Role of lactobacillus cell surface hydrophobicity as probed by AFM in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo Rodriguez, Virginia; Busscher, Hendrik; van der Mei, Henderina; Norde, Willem; de Vries, Jacob

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  7. Role of lactobacillus cell surface hydrophobicity as probed by AMF in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo-Rodriguez, V.; Busscher, H.J.; Meij, van der H.C.; Vries, de J.; Norde, W.

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  8. Biofilm retention on surfaces with variable roughness and hydrophobicity

    DEFF Research Database (Denmark)

    Tang, Lone; Pillai, Saju; Revsbech, Niels Peter

    2011-01-01

    Biofilms on food processing equipment cause food spoilage and pose a hazard to consumers. The bacterial community on steel surfaces in a butcher’s shop was characterized, and bacteria representative of this community enriched from minced pork were used to study biofilm retention. Stainless steel......-gel, but the bacterial community contained fewer Pseudomonas cells. In conclusion, biofilm retention was affected more by surface roughness than chemical composition under the condition described in this study....

  9. Super-hydrophobic surfaces improve corrosion resistance of copper in seawater

    International Nuclear Information System (INIS)

    Liu, Tao; Yin, Yansheng; Chen, Shougang; Chang, Xueting; Cheng, Sha

    2007-01-01

    Pretreated by a n-tetradecanoic acid (CH 3 (CH 2 ) 12 COOH) etch, the super-hydrophobic film was formed on the fresh copper surface. The film structure was probed with contact angle measurement and scanning electron microscopy (SEM). The results suggest that the structure of the film is similar to haulm or flower and the seawater contact angle is larger than 150 o . Moreover, the corrosion resistance of bare and modified samples in seawater were investigated by cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS). Experimental results show that the corrosion rate of Cu with super-hydrophobic surface decreases dramatically because of its special microstructure

  10. Investigating plantation-induced near-surface soil hydrophobicity and its impact on groundwater recharge in the Nebraska Sand Hills, USA

    Science.gov (United States)

    Adane, Z. A.; Nasta, P.; Gates, J. B.

    2014-12-01

    Although numerous studies in diverse environmental settings have demonstrated that plantations tend to reduce soil moisture and recharge rates, research on physical mechanisms affecting these linkages tend to focus mainly on the effects of evapotranspiration and interception. This study investigates the extent of soil hydrophobicity resulting from land use changes and its impact on groundwater recharge in a century-old experimental forest surrounded by grassland in the Northern High Plains (Nebraska National Forest). Water Drop Penetration Tests (WDPT) and Nuclear Magnetic Resonance (NMR) spectroscopy were used to investigate soil hydrophobicity on 50 cm soil cores collected from experimental plots beneath 5 land cover types. WDPT analysis indicated that most near-surface soils (0-12.5 and 12.5-25 cm) beneath pine plots were moderately to strongly hydrophobic. NMR spectroscopy analysis comparing ratios of hydrophobic (3.2-0.5 and 8.5-6.5 ppm) to hydrophilic (6.5-3.2 ppm) regions suggests that surface soils beneath the plantations were uniformly more hydrophobic than grasslands (by ~30 to 260%). Unsaturated zone soil cores were collected from beneath each experimental plot for comparison of hydrophobicity with recharge rates based on chloride and sulfate mass balance. Recharge estimates beneath the plantations (4-10 mm yr-1) represent reductions of 86-94% relative to the surrounding native grassland, suggesting a link between soil hydrophobicity and reduced infiltration beneath the plantations.

  11. ZnO nanowires coated hydrophobic surfaces for various biomedical ...

    Indian Academy of Sciences (India)

    71

    which is typically found in water and can cause special type of pneumonia known as. Legionnaries disease. Because, if the material surface is hydrophilic the bacteria's present in water may adhere to the biomaterial resulting in bio-film formation, which may cause pathogenesis [8-10]. For achieving antibacterial activity, ...

  12. Design of textured surfaces for super-hydrophobicity

    Indian Academy of Sciences (India)

    Prithvi Raj Jelia

    2017-11-11

    Nov 11, 2017 ... phobic surfaces. Phys. Fluids 21(5): 052001. [21] Xiu Y, Zhu L, Hess D and Wong C P 2006 Superhy- drophobicity and UV stability of polydimethylsiloxane/ polytetrafluoroethylene (PDMS/PTFE) coatings. In: Pro- ceedings of the 11th IEEE CPMT International Symposium and Exhibition on Advanced ...

  13. Hydrophobic and Electrostatic Cell Surface Properties of Thermophilic Dairy Streptococci

    NARCIS (Netherlands)

    Van der Mei, HC; de Vries, Jacob; Busscher, HJ

    1993-01-01

    Microbial adhesion to hydrocarbons (MATH) and microelectrophoresis were done in 10 mM potassium phosphate solutions to characterize the surfaces of thermophilic dairy streptococci, isolated from pasteurizers. Regardless of whether they were grown (in M17 broth) with lactose, sucrose, or glucose

  14. Standard Test Method for Hydrophobic Surface Films by the Water-Break Test

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2002-01-01

    1.1 This test method covers the detection of the presence of hydrophobic (nonwetting) films on surfaces and the presence of hydrophobic organic materials in processing ambients. When properly conducted, the test will enable detection of molecular layers of hydrophobic organic contaminants. On very rough or porous surfaces, the sensitivity of the test may be significantly decreased. 1.2 The values stated in SI units are to be regarded as the standard. The inch-pound values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  15. Creation of hydrophobic surfaces using a paint containing functionalized oxide particles

    Science.gov (United States)

    Sino, Paul Albert L.; Herrera, Marvin U.; Balela, Mary Donnabelle L.

    2017-05-01

    Hydrophobic surfaces were created by coating various substrates (aluminum sheet, soda-lime glass, silicon carbide polishing paper, glass with double-sided adhesive) with paint containing functionalized oxide particles. The paint was created by functionalizing oxide particles (ground ZnO, TiO2 nanoparticles, or TiO2 microparticles) with fluorosilane molecules in absolute ethanol. Water contact angle of samples shows that the coated substrate becomes hydrophobic (water contact angle ≥ 90°). Among the oxides that were used, ground ZnO yielded contact angle exemplifying superhydrophobicity (water contact angle ≥ 150°). Scanning electron micrograph of paint-containing TiO2 nanoparticles shows rough functionalized oxides structures which probably increase the hydrophobicity of the surface.

  16. Standard Test Method for Hydrophobic Surface Films by the Atomizer Test

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1965-01-01

    1.1 This test method covers the detection of the presence of hydrophobic (nonwetting) films on surfaces and the presence of hydrophobic organic materials in processing ambients. When properly conducted, the test will enable detection of fractional molecular layers of hydrophobic organic contaminants. On very rough or porous surfaces the sensitivity of the test may be significantly decreased. 1.2 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  17. Molecular dynamics simulations study of nano bubble attachment at hydrophobic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiaqi; Dang, Liem X.; Miller, Jan D.

    2018-01-01

    Bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS) for the first time. The simulation involves a nitrogen nano bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at molybdenite surfaces. During a simulation period of 1 ns, film rupture and displacement occurs. The attached nanobubble at the hydrophobic molybdenite face surface results in a contact angle of about 90º. This spontaneous attachment is due to a “water exclusion zone” at the molybdenite face surface and can be explained by a van der Waals (vdW) attractive force, as discussed in the literature. In contrast, the film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles determined from MD simulations are reported, and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. Interfacial water molecules at the hydrophobic molybdenite face surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed by the presence of a 3 Å “water exclusion zone” at the molybdenite/water interface. The molybdenite armchair-edge and zigzag-edge surfaces show a comparably slow process for film rupture and displacement when compared to the molybdenite face surface, which is consistent with their relatively weak hydrophobic character.

  18. Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine.

    Science.gov (United States)

    Dong, Aixue; Fan, Xuerong; Wang, Qiang; Yu, Yuanyuan; Cavaco-Paulo, Artur

    2015-08-01

    Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI-TOF MS, (1)H NMR, (13)C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5 min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Fabrication and surface properties of hydrophobic barium sulfate aggregates based on sodium cocoate modification

    Science.gov (United States)

    Hu, Linna; Wang, Guangxiu; Cao, Rong; Yang, Chun; Chen, Xi

    2014-10-01

    Hydrophobic barium sulfate aggregates were fabricated by the direction of cocoate anions. At 30 °C, when the weight ratio of sodium cocoate to BaSO4 particles was 2.0 wt.%, the active ratio of the product reached 99.43% and the contact angle was greater than 120°. This method could not only simplify the complex modification process, but reduce energy consumption. The surface morphology, chemical structure and composition of BaSO4 aggregates were characterized by SEM, XRD, and FTIR. The results indicated that the as-synthesized BaSO4 particles were almond-liked and were composed of many interconnected nanoballs and that their surfaces were affected by cocoate anions. The adsorption of cocoate anions reversed the charge and weakened the surface polarity of BaSO4 particles, driving the formation of aggregates. And cocoate anions induced a change of the BaSO4 particles surface from hydrophilic to hydrophobic by a self-assembly and transformation process. Due to the self-assembled structure and the surface hydrophobicity, when adding the hydrophobic BaSO4 into PVC, the mechanical properties of PVC composite materials were significantly improved.

  20. Super-hydrophobic surfaces of SiO₂-coated SiC nanowires: fabrication, mechanism and ultraviolet-durable super-hydrophobicity.

    Science.gov (United States)

    Zhao, Jian; Li, Zhenjiang; Zhang, Meng; Meng, Alan

    2015-04-15

    The interest in highly water-repellent surfaces of SiO2-coated SiC nanowires has grown in recent years due to the desire for self-cleaning and anticorrosive surfaces. It is imperative that a simple chemical treatment with fluoroalkylsilane (FAS, CF3(CF2)7CH2CH2Si(OC2H5)3) in ethanol solution at room temperature resulted in super-hydrophobic surfaces of SiO2-coated SiC nanowires. The static water contact angle of SiO2-coated SiC nanowires surfaces was changed from 0° to 153° and the morphology, microstructure and crystal phase of the products were almost no transformation before and after super-hydrophobic treatment. Moreover, a mechanism was expounded reasonably, which could elucidate the reasons for their super-hydrophobic behavior. It is important that the super-hydrophobic surfaces of SiO2-coated SiC nanowires possessed ultraviolet-durable (UV-durable) super-hydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Surface tension, hydrophobicity, and black holes: The entropic connection

    International Nuclear Information System (INIS)

    Callaway, D.J.

    1996-01-01

    The geometric entropy arising from partitioning space in a fluid open-quote open-quote field theory close-quote close-quote is shown to be linearly proportional to the area of an excluded region. The coefficient of proportionality is related to surface tension by a thermodynamic argument. Good agreement with experimental data is obtained for a number of fluids. The calculation employs a density-matrix formalism developed previously for studying the origin of black hole entropy. This approach may lead to a practical technique for the evaluation of thermodynamic quantities with important entropic components. copyright 1996 The American Physical Society

  2. Drag reduction in reservoir rock surface: Hydrophobic modification by SiO{sub 2} nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yong-Li, E-mail: yylhill@163.com [College of Chemistry & Chemical Engineering, Xi’an Shiyou University, Xi’an 710065 (China); Cui, Ming-Yue; Jiang, Wei-Dong; He, An-Le; Liang, Chong [Langfang Branch of Research Institute of Petroleum Exploration & Development, Langfang 065007 (China)

    2017-02-28

    Graphical abstract: The micro-nanoscale hierarchical structures at the sandstone core surface are constructed by adsorption of the modified silica nanoparticles, which leads to the effect of drag reduction to improve the low injection rate in ultra-low permeability reservoirs. - Highlights: • A micro-nanoscale hierarchical structure is formed at the reservoir rock surface. • An inversion has happened from hydrophilic into hydrophobic modified by nanofluids. • The effect of drag reduction to improve the low injection rate is realized. • The mechanism of drag reduction induced from the modified core surface was unclosed. - Abstract: Based on the adsorption behavior of modified silica nanoparticles in the sandstone core surface, the hydrophobic surface was constructed, which consists of micro-nanoscale hierarchical structure. This modified core surface presents a property of drag reduction and meets the challenge of high injection pressure and low injection rate in low or ultra-low permeability reservoir. The modification effects on the surface of silica nanoparticles and reservoir cores, mainly concerning hydrophobicity and fine structure, were determined by measurements of contact angle and scanning electron microscopy. Experimental results indicate that after successful modification, the contact angle of silica nanoparticles varies from 19.5° to 141.7°, exhibiting remarkable hydrophobic properties. These modified hydrophobic silica nanoparticles display a good adsorption behavior at the core surface to form micro-nanobinary structure. As for the wettability of these modified core surfaces, a reversal has happened from hydrophilic into hydrophobic and its contact angle increases from 59.1° to 105.9°. The core displacement experiments show that the relative permeability for water has significantly increased by an average of 40.3% via core surface modification, with the effects of reducing injection pressure and improving injection performance of water

  3. Drag reduction in reservoir rock surface: Hydrophobic modification by SiO2 nanofluids

    International Nuclear Information System (INIS)

    Yan, Yong-Li; Cui, Ming-Yue; Jiang, Wei-Dong; He, An-Le; Liang, Chong

    2017-01-01

    Graphical abstract: The micro-nanoscale hierarchical structures at the sandstone core surface are constructed by adsorption of the modified silica nanoparticles, which leads to the effect of drag reduction to improve the low injection rate in ultra-low permeability reservoirs. - Highlights: • A micro-nanoscale hierarchical structure is formed at the reservoir rock surface. • An inversion has happened from hydrophilic into hydrophobic modified by nanofluids. • The effect of drag reduction to improve the low injection rate is realized. • The mechanism of drag reduction induced from the modified core surface was unclosed. - Abstract: Based on the adsorption behavior of modified silica nanoparticles in the sandstone core surface, the hydrophobic surface was constructed, which consists of micro-nanoscale hierarchical structure. This modified core surface presents a property of drag reduction and meets the challenge of high injection pressure and low injection rate in low or ultra-low permeability reservoir. The modification effects on the surface of silica nanoparticles and reservoir cores, mainly concerning hydrophobicity and fine structure, were determined by measurements of contact angle and scanning electron microscopy. Experimental results indicate that after successful modification, the contact angle of silica nanoparticles varies from 19.5° to 141.7°, exhibiting remarkable hydrophobic properties. These modified hydrophobic silica nanoparticles display a good adsorption behavior at the core surface to form micro-nanobinary structure. As for the wettability of these modified core surfaces, a reversal has happened from hydrophilic into hydrophobic and its contact angle increases from 59.1° to 105.9°. The core displacement experiments show that the relative permeability for water has significantly increased by an average of 40.3% via core surface modification, with the effects of reducing injection pressure and improving injection performance of water

  4. Co-deposition of tannic acid and diethlyenetriamine for surface hydrophilization of hydrophobic polymer membranes

    Science.gov (United States)

    Zhang, Xi; Ren, Peng-Fei; Yang, Hao-Cheng; Wan, Ling-Shu; Xu, Zhi-Kang

    2016-01-01

    We report a novel approach toward the surface modification of commercial polymer membranes via co-deposition of tannic acid (TA) and diethlyenetriamine (DETA). Particle-free, superhydrophilic, and almost colorless coatings are fabricated on the surfaces of polypropylene, poly(vinylidene fluoride), and poly(tetrafluoroethlene) microfiltration membranes. Cross-linking between TA and DETA plays a crucial role during the co-deposition process, as well as the adhesion of TA on the hydrophobic membrane surfaces. Both the surface wettability and water permeation flux are dramatically improved for the studied membranes after the co-deposition. The results indicate that co-deposition of TA and DETA is great potential for the surface modification of hydrophobic membranes.

  5. Hydrophobization of track membrane surface by ion-plasma sputtering method

    Science.gov (United States)

    Kuklin, I. E.; Khlebnikov, N. A.; Barashev, N. R.; Serkov, K. V.; Polyakov, E. V.; Zdorovets, M. V.; Borgekov, D. B.; Zhidkov, I. S.; Cholakh, S. O.; Kozlovskiy, A. L.

    2017-09-01

    This article reviews the possibility of applying inorganic coatings of metal compounds on PTM by ion-plasma sputtering. The main aim of this research is to increase the contact angle of PTM surfaces and to impart the properties of a hydrophobic material to it. After the modification, the initial contact angle increased from 70° to 120°.

  6. Effect of Growth Conditions on Flocculation and Cell Surface Hydrophobicity of Brewing Yeast

    Czech Academy of Sciences Publication Activity Database

    Kopecká, J.; Němec, M.; Matoulková, D.; Čejka, P.; Jelínková, Markéta; Felsberg, Jürgen; Sigler, Karel

    2015-01-01

    Roč. 73, č. 2 (2015), s. 143-150 ISSN 0361-0470 Institutional support: RVO:61388971 Keywords : Ale and lager yeast * Cell surface hydrophobicity * FLO genes Subject RIV: EI - Biotechnology ; Bionics Impact factor: 0.492, year: 2015

  7. IMPLICATIONS OF MICROBIAL ADHESION TO HYDROCARBONS FOR EVALUATING CELL-SURFACE HYDROPHOBICITY .2. ADHESION MECHANISMS

    NARCIS (Netherlands)

    VANDERMEI, HC; VANDEBELTGRITTER, B; BUSSCHER, HJ

    1995-01-01

    Microbial adhesion to hydrocarbons (MATH) is generally considered to be a measure of the organisms cell surface hydrophobicity. Recent observations that the zeta potentials of hydrocarbons can be highly negative in the various solutions commonly used in MATH, have suggested that MATH may measure a

  8. Surface hydrophobicity of Aspergillus nidulans conidiospores and its role in pellet formation

    DEFF Research Database (Denmark)

    Dynesen, Jens Østergaard; Nielsen, Jens

    2003-01-01

    Formation of pellets by Aspergillus nidulans is primarily due to agglomeration of the fungal conidiospores. Although agglomeration of conidiospores has been known for a long time, its mechanism has not been clearly elucidated. To study the influence of the fungal conidiospore wall hydrophobicity...... on conidiospore agglomeration, pellet formation of an A. nidulans wild type and strains deleted in the conidiospore-wall-associated hydrophobins DewA and RodA was compared at different pH values. From contact angle measurements, RodA was found to be more important for the surface hydrophobicity than Dew...

  9. RF plasma based selective modification of hydrophilic regions on super hydrophobic surface

    International Nuclear Information System (INIS)

    Lee, Jaehyun; Hwang, Sangyeon; Cho, Dae-Hyun; Hong, Jungwoo; Shin, Jennifer H.; Byun, Doyoung

    2017-01-01

    Highlights: • Simple and amenable reforming method for a substrate with disparate patterns of hydrophilic dots on super-hydrophobic surfaces is proposed. • Wettability characteristics and modification mechanism for the surfaces are conducted and revealed through SEM, AFM, WSI, and SIMS. • Several representative materials for various applications are successfully deposited. - Abstract: Selective modification and regional alterations of the surface property have gained a great deal of attention to many engineers. In this paper, we present a simple, a cost-effective, and amendable reforming method for disparate patterns of hydrophilic regions on super-hydrophobic surfaces. Uniform super-hydrophobic layer (Contact angle; CA > 150°, root mean square (RMS) roughness ∼0.28 nm) can be formed using the atmospheric radio frequency (RF) plasma on top of the selective hydrophilic (CA ∼ 70°, RMS roughness ∼0.34 nm) patterns imprinted by electrohydrodynamic (EHD) jet printing technology with polar alcohols (butyl carbitol or ethanol). The wettability of the modified surface was investigated qualitatively utilizing scanning electron microscopy (SEM), atomic force microscopy (AFM), and wavelength scanning interferometer (WSI). Secondary ion mass spectroscopy (SIMS) analysis showed that the alcohol addiction reaction changed the types of radicals on the super-hydrophobic surface. The wettability was found to depend sensitively on chemical radicals on the surface, not on surface morphology (particle size and surface roughness). Furthermore, three different kinds of representative hydrophilic samples (polystyrene nano-particle aqueous solution, Salmonella bacteria medium, and poly(3,4-ethylenediocythiophene) ink) were tested for uniform deposition onto the desired hydrophilic regions. This simple strategy would have broad applications in various research fields that require selective deposition of target materials.

  10. RF plasma based selective modification of hydrophilic regions on super hydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jaehyun; Hwang, Sangyeon; Cho, Dae-Hyun [Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Hong, Jungwoo [Department of Mechanical Engineering, Graduate of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141 (Korea, Republic of); Shin, Jennifer H., E-mail: j_shin@kaist.ac.kr [Department of Mechanical Engineering, Graduate of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141 (Korea, Republic of); Byun, Doyoung, E-mail: dybyun@skku.edu [Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of)

    2017-02-01

    Highlights: • Simple and amenable reforming method for a substrate with disparate patterns of hydrophilic dots on super-hydrophobic surfaces is proposed. • Wettability characteristics and modification mechanism for the surfaces are conducted and revealed through SEM, AFM, WSI, and SIMS. • Several representative materials for various applications are successfully deposited. - Abstract: Selective modification and regional alterations of the surface property have gained a great deal of attention to many engineers. In this paper, we present a simple, a cost-effective, and amendable reforming method for disparate patterns of hydrophilic regions on super-hydrophobic surfaces. Uniform super-hydrophobic layer (Contact angle; CA > 150°, root mean square (RMS) roughness ∼0.28 nm) can be formed using the atmospheric radio frequency (RF) plasma on top of the selective hydrophilic (CA ∼ 70°, RMS roughness ∼0.34 nm) patterns imprinted by electrohydrodynamic (EHD) jet printing technology with polar alcohols (butyl carbitol or ethanol). The wettability of the modified surface was investigated qualitatively utilizing scanning electron microscopy (SEM), atomic force microscopy (AFM), and wavelength scanning interferometer (WSI). Secondary ion mass spectroscopy (SIMS) analysis showed that the alcohol addiction reaction changed the types of radicals on the super-hydrophobic surface. The wettability was found to depend sensitively on chemical radicals on the surface, not on surface morphology (particle size and surface roughness). Furthermore, three different kinds of representative hydrophilic samples (polystyrene nano-particle aqueous solution, Salmonella bacteria medium, and poly(3,4-ethylenediocythiophene) ink) were tested for uniform deposition onto the desired hydrophilic regions. This simple strategy would have broad applications in various research fields that require selective deposition of target materials.

  11. Fabrication of super-hydrophobic surfaces on aluminum alloy substrates by RF-sputtered polytetrafluoroethylene coatings

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-03-01

    Full Text Available In this work, we present a method of fabricating super-hydrophobic surface on aluminum alloy substrate. The etching of aluminum surfaces has been performed using Beck's dislocation etchant for different time to create micrometer-sized irregular steps. An optimised etching time of 50 s is found to be essential before polytetrafluoroethylene (PTFE coating, to obtain a highest water contact angle of 165±2° with a lowest contact angle hysteresis as low as 5±2°. The presence of patterned microstructure as revealed by scanning electron microscopy (SEM together with the low surface energy ultrathin RF-sputtered PTFE films renders the aluminum alloy surfaces highly super-hydrophobic.

  12. Construction of super - hydrophobic copper alloy surface by one - step mixed solution immersion method

    Science.gov (United States)

    Gu, Qiang; Chen, Ying; Chen, Dong; Zhang, Zeting

    2018-01-01

    This paper presents a method for preparing a super hydrophobic surface with a fast, simple, low-cost, one-step reaction by immersing copper alloy in an ethanol solution containing silver nitrate and myristic acid. The effects of reaction time, reaction temperature, reactant concentration and reaction time on the wettability of the material were studied. The surface wettability, appearance, chemical composition, durability and chemical stability of the prepared samples was measured by water contact angle (CA), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results show that when the reaction time is only 10min, the surface WCA of the prepared material can reach 154.9. This study provides an effective method for the rapid preparation of stable super hydrophobic surfaces.

  13. Hydrophobic Surfaces: Topography Effects on Wetting by Supercooled Water and Freezing Delay

    DEFF Research Database (Denmark)

    Heydari, Golrokh; Thormann, Esben; Järn, Mikael

    2013-01-01

    Hydrophobicity, and in particular superhydrophobicity, has been extensively considered to promote ice-phobicity. Dynamic contact angle measurements above 0 °C have been widely used to evaluate the water repellency. However, it is the wetting properties of supercooled water at subzero temperatures...... surfaces in either the Wenzel or the Cassie–Baxter state as characterized by water contact angle measurements at room temperature. We find that the water freezing delay time is not significantly affected by the surface topography and discuss this finding within the classical theory of heterogeneous...... and the derived work of adhesion that are important for applications dealing with icing. In this work we address this issue by determining the temperature-dependent dynamic contact angle of microliter-sized water droplets on a smooth hydrophobic and a superhydrophobic surface with similar surface chemistry...

  14. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal.

    Science.gov (United States)

    Li, Lin; Liu, Suqin; Liu, Junxin

    2011-08-30

    In this study, coconut shell based carbons were chemically treated by ammonia, sodium hydroxide, nitric acid, sulphuric acid, and phosphoric acid to determine suitable modification for improving adsorption ability of hydrophobic volatile organic compounds (VOCs) on granular activated carbons (GAC). The saturated adsorption capacities of o-xylene, a hydrophobic volatile organic compound, were measured and adsorption effects of the original and modified activated carbons were compared. Results showed that GAC modified by alkalis had better o-xylene adsorption capacity. Uptake amount was enhanced by 26.5% and reduced by 21.6% after modification by NH(3)H(2)O and H(2)SO(4), respectively. Compared with the original, GAC modified by acid had less adsorption capacity. Both SEM/EDAX and BET were used to identify the structural characteristics of the tested GAC, while IR spectroscopy and Boehm's titration were applied to analysis the surface functional groups. Relationships between physicochemical characteristics of GAC and their adsorption performances demonstrated that o-xylene adsorption capacity was related to surface area, pore volume, and functional groups of the GAC surface. Removing surface oxygen groups, which constitute the source of surface acidity, and reducing hydrophilic carbon surface favors adsorption capacity of hydrophobic VOCs on carbons. The performances of modified GACs were also investigated in the purification of gases containing complex components (o-xylene and steam) in the stream. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Engineering durable hydrophobic surfaces on porous alumina ceramics using in-situ formed inorganic-organic hybrid nanoparticles

    NARCIS (Netherlands)

    Gu, Jianqiang; Wang, Junwei; Li, Yanan; Xu, Xin; Chen, Chusheng; Winnubst, Louis

    2017-01-01

    Hydrophobic surfaces are required for a variety of applications owing to their water repellent and self-cleaning properties. In this work, we present a novel approach to prepare durable hydrophobic surfaces on porous ceramics. A polydimethylsiloxane (PDMS) film was applied to a porous alumina wafer,

  16. Fluorine-Terminated Diamond Surfaces as Dense Dipole Lattices: The Electrostatic Origin of Polar Hydrophobicity.

    Science.gov (United States)

    Mayrhofer, Leonhard; Moras, Gianpietro; Mulakaluri, Narasimham; Rajagopalan, Srinivasan; Stevens, Paul A; Moseler, Michael

    2016-03-30

    Despite the pronounced polarity of C-F bonds, many fluorinated carbon compounds are hydrophobic: a controversial phenomenon known as "polar hydrophobicity". Here, its underlying microscopic mechanisms are explored by ab initio calculations of fluorinated and hydrogenated diamond (111) surfaces interacting with single water molecules. Gradient- and van der Waals-corrected density functional theory simulations reveal that "polar hydrophobicity" of the fully fluorinated surfaces is caused by a negligible surface/water electrostatic interaction. The densely packed C-F surface dipoles generate a short-range electric field that decays within the core repulsion zone of the surface and hence vanishes in regions accessible by adsorbates. As a result, water physisorption on fully F-terminated surfaces is weak (adsorption energies Ead 0.2 eV) that is dominated by electrostatic interactions. The suppression of electrostatic interactions also holds for perfluorinated molecular carbon compounds, thus explaining the prevalent hydrophobicity of fluorocarbons. In general, densely packed polar terminations do not always lead to short-range electric fields. For example, surfaces with substantial electron density spill-out give rise to electric fields with a much slower decay. However, electronic spill-out is limited in F/H-terminated carbon materials. Therefore, our ab initio results can be reproduced and rationalized by a simple classical point-charge model. Consequently, classical force fields can be used to study the wetting of F/H-terminated diamond, revealing a pronounced correlation between adsorption energies of single H2O molecules and water contact angles.

  17. Fabrication of semi-transparent super-hydrophobic surface based on silica hierarchical structures

    KAUST Repository

    Chen, Ping-Hei

    2011-01-01

    This study successfully develops a versatile method of producing superhydrophobic surfaces with micro/nano-silica hierarchical structures on glass surfaces. Optically transparent super hydrophobic silica thin films were prepared by spin-coating silica particles suspended in a precursor solution of silane, ethanol, and H2O with molar ratio of 1:4:4. The resulting super hydrophobic films were characterized by scanning electron microscopy (SEM), optical transmission, and contact angle measurements. The glass substrates in this study were modified with different particles: micro-silica particles, nano-silica particles, and hierarchical structures. This study includes SEM micrographs of the modified glass surfaces with hierarchical structures at different magnifications. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  18. Corrosion behavior of super-hydrophobic surface on copper in seawater

    Energy Technology Data Exchange (ETDEWEB)

    Liu Tao; Chen Shougang; Cheng Sha; Tian Jintao; Chang Xueting [Institute of Materials Science and Engineering, Ocean University of China, Qingdao 266100 (China); Yin Yansheng [Institute of Materials Science and Engineering, Ocean University of China, Qingdao 266100 (China)], E-mail: yys2003@ouc.edu.cn

    2007-11-01

    A novel super-hydrophobic film was prepared by myristic acid (n-tetradecanoic) chemically adsorbed onto the copper wafer. The film formation and its structure were characterized by means of water contact angle measurement, Fourier transformation infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The static contact angle for water on the surface of this organic film was measured to be as high as 158{sup o}. The formation of a composite interface composed of the flower-like surface nanostructures, water droplet and air trapped in the crevices was suggested to be responsible for the superior water-repellent property. The corrosion behavior of the super-hydrophobic surface was investigated with potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Due to the 'air valleys' and 'capillarity' effects, the corrosion resistance of the material was improved remarkably.

  19. Corrosion behavior of super-hydrophobic surface on copper in seawater

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tao; Chen, Shougang; Cheng, Sha; Tian, Jintao; Chang, Xueting; Yin, Yansheng [Institute of Materials Science and Engineering, Ocean University of China, Qingdao 266100 (China)

    2007-11-01

    A novel super-hydrophobic film was prepared by myristic acid (n-tetradecanoic) chemically adsorbed onto the copper wafer. The film formation and its structure were characterized by means of water contact angle measurement, Fourier transformation infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The static contact angle for water on the surface of this organic film was measured to be as high as 158 . The formation of a composite interface composed of the flower-like surface nanostructures, water droplet and air trapped in the crevices was suggested to be responsible for the superior water-repellent property. The corrosion behavior of the super-hydrophobic surface was investigated with potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Due to the 'air valleys' and 'capillarity' effects, the corrosion resistance of the material was improved remarkably. (author)

  20. Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2015-04-01

    Full Text Available We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H2O, and then in boiling water and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

  1. Effects of Streptococcus sanguinis Bacteriocin on Cell Surface Hydrophobicity, Membrane Permeability, and Ultrastructure of Candida Thallus

    Directory of Open Access Journals (Sweden)

    Shengli Ma

    2015-01-01

    Full Text Available Candida albicans (C.a and Candida tropicalis (C.t were treated with Streptococcus sanguinis bacteriocin (S.s bacteriocin, respectively; the bacteriostatic dynamics of S.s bacteriocin, their effects on cell surface hydrophobicity, leakage of inorganic phosphorus and macromolecular substance, cytosolic calcium concentration, and ultrastructure changes of Candida thallus were detected and analyzed. The results showed that inhibitory effect of S.s bacteriocin on C.a and C.t reached peak level at 24 h, the cell-surface hydrophobicity decreased significantly (P < 0.05 after S.s bacteriocin treatment, and there was leakage of cytoplasmic inorganic phosphorus and macromolecular substance from C.a and C.t; cytosolic calcium concentration decreased greatly. After 24 h treatment by S.s bacteriocin, depressive deformity and defect could be found in the cell surface of C.a and C.t; the thallus displayed irregular forms: C.a was shrunken, there was unclear margins abutting upon cell wall and cell membrane, nucleus disappeared, and cytoplasm was inhomogeneous; likewise, C.t was first plasmolysis, and then the cytoplasm was shrunk, the ultrastructure of cell wall and cell membrane was continuously damaged, and the nucleus was karyolysis. It was illustrated that S.s bacteriocin had similar antifungal effect on C.a and C.t; their cell surface hydrophobicity, membrane permeability, and ultrastructure were changed significantly on exposure to S.s bacteriocin.

  2. Hydrophobicity, surface tension, and zeta potential measurements of glass-reinforced hydroxyapatite composites.

    Science.gov (United States)

    Lopes, M A; Monteiro, F J; Santos, J D; Serro, A P; Saramago, B

    1999-06-15

    Wettability and zeta potential studies were performed to characterize the hydrophobicity, surface tension, and surface charge of P2O5-glass-reinforced hydroxyapatite composites. Quantitative phase analysis was performed by the Rietveld method using GSAS software applied to X-ray diffractograms. Surface charge was assessed by zeta potential measurements. Protein adsorption studies were performed using vitronectin. Contact angles and surface tensions variation with time were determined by the sessile and pendent drop techniques, respectively, using ADSA-P software. The highest (-18.1 mV) and lowest (-28.7 mV) values of zeta potential were found for hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), respectively, with composite materials presenting values in between. All studied bioceramic materials showed similar solid surface tension. For HA and beta-TCP, solid surface tensions of 46.7 and 45.3 mJ/m2, respectively, were obtained, while composites presented intermediate surface tension values. The dispersive component of surface tension was the predominant one for all materials studied. Adhesion work values between the vitronectin solution and HA and beta-TCP were found to be 79.8 and 88.0 mJ/m2, respectively, while the 4.0 wt % glass composites showed slightly lower values than the 2.5 wt % ones. The presence of beta-TCP influenced surface charge, hydrophobicity, and protein adsorption of the glass-reinforced HA composites, and therefore indirectly affected cell-biomaterial interactions.

  3. Effect on cell surface hydrophobicity and susceptibility of Helicobacter pylori to medicinal plant extracts.

    Science.gov (United States)

    Annuk, H; Hirmo, S; Türi, E; Mikelsaar, M; Arak, E; Wadström, T

    1999-03-01

    Effects on aqueous extracts of medicinal plants on ten Helicobacter pylori strains were studied by the salt aggregation test to determine the possibility to modulate their cell surface hydrophobicity and by an agar diffusion assay for detection of antimicrobial activity. It was established that aqueous extracts of bearberry and cowberry leaves enhance cell aggregation of all H. pylori strains tested by the salt aggregation test, and the extract of bearberry possessed a remarkable bacteriostatic activity. Pure tannic acid showed a result similar to that of bearberry and cowberry extracts which contained a large amount of tannins. In contrast, extracts of wild camomile and pineapple-weed, which blocked aggregation of H. pylori, contained small amounts of tannins and did not reveal any antimicrobial activity. Tannic acid seems to be the component of bearberry and cowberry aqueous extracts with the highest activity to decrease cell surface hydrophobicity as well as in antibacterial activity against H. pylori.

  4. Cell surface hydrophobicity: a key component in the degradation of polyethylene succinate by Pseudomonas sp. AKS2.

    Science.gov (United States)

    Tribedi, P; Sil, A K

    2014-02-01

    Polyethylene succinate (PES) contains hydrolysable ester bonds that make it a potential substitute for polyethylene (PE) and polypropylene (PP). Towards bioremediation of PES, we have already reported that a new strain of Pseudomonas, Pseudomonas sp. AKS2, can efficiently degrade PES and hypothesized that cell surface hydrophobicity plays an important role in this degradation process. In this study, our efforts were targeted towards establishing a correlation between cell surface hydrophobicity and PES degradation. We have manipulated cell surface hydrophobicity of AKS2 by varying concentrations of glucose and ammonium sulphate in the growth medium and subsequently examined the extent of PES degradation. We observed an increase in PES degradation by AKS2 with an increase in cell surface hydrophobicity. The increased surface hydrophobicity caused an enhanced biofilm formation on PES surface that resulted in better polymer degradation. The current study establishes a direct correlation between cell surface hydrophobicity of an organism and its potential to degrade a nonpolar polymer like PES. Cell surface hydrophobicity manipulation can be used as an important strategy to increase bioremediation of nonpolar polymer like PES. © 2013 The Society for Applied Microbiology.

  5. Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

    International Nuclear Information System (INIS)

    Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

    2013-01-01

    As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO 3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH 3 (CH 2 ) 11 Si(OCH 3 ) 3 ). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro–nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

  6. Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yan; Yin, Xiaoming; Zhang, Jijia [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); Wang, Yaming [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Han, Zhiwu, E-mail: zwhan@jlu.edu.cn [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); Ren, Luquan [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China)

    2013-09-01

    As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO{sub 3} solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH{sub 3}(CH{sub 2}){sub 11}Si(OCH{sub 3}){sub 3}). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro–nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

  7. Comparison of SF₆ and CF₄ Plasma Treatment for Surface Hydrophobization of PET Polymer.

    Science.gov (United States)

    Resnik, Matic; Zaplotnik, Rok; Mozetic, Miran; Vesel, Alenka

    2018-02-21

    The fluorination of the polymer polyethylene terephthalate in plasma created from SF₆ or CF₄ gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF₆ and CF₄ gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF₆ plasma, was explained by the electronegativity of both gases.

  8. Comparison of SF6 and CF4 Plasma Treatment for Surface Hydrophobization of PET Polymer

    Science.gov (United States)

    Mozetic, Miran

    2018-01-01

    The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF6 and CF4 gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF6 plasma, was explained by the electronegativity of both gases. PMID:29466293

  9. Analyzing the Molecular Kinetics of Water Spreading on Hydrophobic Surfaces via Molecular Dynamics Simulation.

    Science.gov (United States)

    Zhao, Lei; Cheng, Jiangtao

    2017-09-07

    In this paper, we report molecular kinetic analyses of water spreading on hydrophobic surfaces via molecular dynamics simulation. The hydrophobic surfaces are composed of amorphous polytetrafluoroethylene (PTFE) with a static contact angle of ~112.4° for water. On the basis of the molecular kinetic theory (MKT), the influences of both viscous damping and solid-liquid retarding were analyzed in evaluating contact line friction, which characterizes the frictional force on the contact line. The unit displacement length on PTFE was estimated to be ~0.621 nm and is ~4 times as long as the bond length of C-C backbone. The static friction coefficient was found to be ~[Formula: see text] Pa·s, which is on the same order of magnitude as the dynamic viscosity of water, and increases with the droplet size. A nondimensional number defined by the ratio of the standard deviation of wetting velocity to the characteristic wetting velocity was put forward to signify the strength of the inherent contact line fluctuation and unveil the mechanism of enhanced energy dissipation in nanoscale, whereas such effect would become insignificant in macroscale. Moreover, regarding a liquid droplet on hydrophobic or superhydrophobic surfaces, an approximate solution to the base radius development was derived by an asymptotic expansion approach.

  10. Hydrophobic modification on surface of chitin sponges for highly effective separation of oil.

    Science.gov (United States)

    Duan, Bo; Gao, Huimin; He, Meng; Zhang, Lina

    2014-11-26

    A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the particular wettability and great porosity. Furthermore, the biodegradation kinetics of the chitin sponge forecasted that the chitin could be completely biodegraded within 32 days by the microorganisms in the soil. This work provided a new pathway to prepare the chitin-based materials for highly effective removal of oil from water, showing potential application in the pollutant remediation field.

  11. Hydrophobic modification of wood via surface-initiated ARGET ATRP of MMA

    Energy Technology Data Exchange (ETDEWEB)

    Fu Yanchun; Li Gang [Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Yu Haipeng, E-mail: yuhaipeng20000@yahoo.com.cn [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Liu Yixing, E-mail: yxl200488@sina.com [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China)

    2012-01-15

    To convert the hydrophilic surface of wood into a hydrophobic surface, the present study investigated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) as a method of grafting methyl methacrylate (MMA) onto the wood surface. The wood treated with 2-bromoisobutyryl bromide and with the subsequently attached MMA via ARGET ATRP under different polymerization times (2 h, 4 h, 6 h, 8 h) were examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. All the analyses confirmed that PMMA had been grafted onto the wood surface. Water contact angle measurement proved that the covering layer of PMMA on wood made the surface hydrophobic. Polymerization time had a positive influence on the contact angle value and higher contact angle can be produced with the prolongation of the polymerization time. When the reaction time was extended to 8 h, the contact angle of treated wood surface reached 130 Degree-Sign in the beginning, and remained at 116 Degree-Sign after 60 s. The ARGET ATRP method may raise an alteration on the wood surface modification.

  12. Dynamic expression of cell surface hydrophobicity during initial yeast cell growth and before germ tube formation of Candida albicans.

    OpenAIRE

    Hazen, B W; Hazen, K C

    1988-01-01

    Expression of cell surface hydrophobicity (CSH) during initial growth of Candida albicans was monitored. CSH of hydrophobic and hydrophilic yeast cells changed within 30 min upon subculture into fresh medium. Morphologic evidence of germination was preceded by expression of CSH. These results indicate that CSH expression is important in C. albicans growth.

  13. Anisotropic wetting characteristics versus roughness on machined surfaces of hydrophilic and hydrophobic materials

    International Nuclear Information System (INIS)

    Liang, Yande; Shu, Liming; Natsu, Wataru; He, Fuben

    2015-01-01

    Graphical abstract: - Highlights: • The aim is to investigate the influence of roughness on anisotropic wetting on machined surfaces. • The relationship between roughness and anisotropic wetting is modeled by thermodynamical analysis. • The effect of roughness on anisotropic wetting on hydrophilic materials is stronger than that on hydrophobic materials. • The energy barrier existing in the direction perpendicular to the lay is one of the main reasons for the anisotropic wetting. • The contact angle in the parallel direction is larger than that in the perpendicular direction. - Abstract: Anisotropic wetting of machined surfaces is widely applied in industries which can be greatly affected by roughness and solid's chemical properties. However, there has not been much work on it. A free-energy thermodynamic model is presented by analyzing geometry morphology of machined surfaces (2-D model surfaces), which demonstrates the influence of roughness on anisotropic wetting. It can be concluded that the energy barrier is one of the main reasons for the anisotropic wetting existing in the direction perpendicular to the lay. In addition, experiments in investigating anisotropic wetting, which was characterized by the static contact angle and droplet's distortion, were performed on machined surfaces with different roughness on hydrophilic and hydrophobic materials. The droplet's anisotropy found on machined surfaces increased with mean slope of roughness profile Kr. It indicates that roughness on anisotropic wetting on hydrophilic materials has a stronger effect than that on hydrophobic materials. Furthermore, the contact angles predicted by the model are basically consistent with the experimentally ones

  14. Texture Analysis of Hydrophobic Polycarbonate and Polydimethylsiloxane Surfaces via Persistent Homology

    Directory of Open Access Journals (Sweden)

    Ali Nabi Duman

    2017-09-01

    Full Text Available Due to recent climate change-triggered, regular dust storms in the Middle East, dust mitigation has become the critical issue for solar energy harvesting devices. One of the methods to minimize and prevent dust adhesion and create self-cleaning abilities is to generate hydrophobic characteristics on surfaces. The purpose of this study is to explore the topological features of hydrophobic surfaces. We use non-standard techniques from topological data analysis to extract morphological features from the AFM images. Our method recovers most of the previous qualitative observations in a robust and quantitative way. Persistence diagrams, which is a summary of topological structures, witness quantitatively that the crystallized polycarbonate (PC surface possesses spherulites, voids, and fibrils, and the texture height and spherulite concentration increases with the increased immersion period. The approach also shows that the polydimethylsiloxane (PDMS exactly copied the structures at the PC surface but 80 to 90 percent of the nanofibrils were not copied at PDMS surface. We next extract a feature vector from each persistence diagram to show which experiments hold features with similar variance using principal component analysis (PCA. The K-means clustering algorithm is applied to the matrix of feature vectors to support the PCA result, grouping experiments with similar features.

  15. Superhydrophobic Polyimide via Ultraviolet Photooxidation: The Evolution of Surface Morphology and Hydrophobicity under Different Ultraviolet Intensities

    Directory of Open Access Journals (Sweden)

    Hongyu Gu

    2015-01-01

    Full Text Available Ultraviolet (UV photooxidation has recently been developed to fabricate superhydrophobic polyimide (PI films in combination with fluoroalkylsilane modification. However, it remains unclear whether the surface morphology and hydrophobicity are sensitive to technical parameters such as UV intensity and radiation environment. Herein, we focus on the effects of UV intensity on PI surface structure and wettability to gain comprehensive understanding and more effective control of this technology. Scanning electron microscopy (SEM and atomic force microscopy (AFM results showed that UV intensity governed the evolutionary pattern of surface morphology: lower UV intensity (5 mW/cm2 facilitated in-plane expansion of dendritic protrusions while stronger UV (10 and 15 mW/cm2 encouraged localized growth of protrusions in a piling-up manner. Surface roughness and hydrophobicity maximized at the intensity of 10 mW/cm2, as a consequence of the slowed horizontal expansion and preferred vertical growth of the protrusions when UV intensity increased. Based on these results, the mechanism that surface micro/nanostructures developed in distinct ways when exposed to different UV intensities was proposed. Though superhydrophobicity (water contact angle larger than 150° can be achieved at UV intensity not less than 10 mW/cm2, higher intensity decreased the effectiveness. Therefore, the UV photooxidation under 10 mW/cm2 for 72 h is recommended to fabricate superhydrophobic PI films.

  16. Adsorption of an endoglucanase from the hyperthermophilic Pyrococcus furiosus on hydrophobic (polystyrene) and hydrophilic (silica) surfaces increases protein heat stability

    NARCIS (Netherlands)

    Koutsopoulos, S.; van der Oost, J.; Norde, Willem

    2004-01-01

    The interaction of an endoglucanase from the hyperthermophilic microorganism Pyrococcus furiosus with two types of surfaces, that is, hydrophobic polystyrene and hydrophilic silica, was investigated, and the adsorption isotherms were determined. The adsorbed hyperthermostable enzyme did not undergo

  17. Construction of Hydrophobic Wood Surface and Mechanical Property of Wood Cell Wall on Nanoscale Modified by Dimethyldichlorosilane

    Science.gov (United States)

    Yang, Rui; Wang, Siqun; Zhou, Dingguo; Zhang, Jie; Lan, Ping; Jia, Chong

    2018-01-01

    Dimethyldichlorosilane was used to improve the hydrophobicity of wood surface. The water contact angle of the treated wood surface increased from 85° to 143°, which indicated increased hydrophobicity. The nanomechanical properties of the wood cell wall were evaluated using a nanoindentation test to analyse the hydrophobic mechanism on the nano scale. The elastic modulus of the cell wall was significantly affected by the concentration but the influence of treatment time is insignificant. The hardness of the cell wall for treated samples was significantly affected by both treatment time and concentration. The interaction between treatment time and concentration was extremely significant for the elastic modulus of the wood cell wall.

  18. Low proliferation and high apoptosis of osteoblastic cells on hydrophobic surface are associated with defective Ras signaling

    International Nuclear Information System (INIS)

    Chang, Eun-Ju; Kim, Hong-Hee; Huh, Jung-Eun; Kim, In-Ae; Seung Ko, Jea; Chung, Chong-Pyoung; Kim, Hyun-Man

    2005-01-01

    The hydrophobic (HPB) nature of most polymeric biomaterials has been a major obstacle in using those materials in vivo due to low compatibility with cells. However, there is little knowledge of the molecular detail to explain how surface hydrophobicity affects cell responses. In this study, we compared the proliferation and apoptosis of human osteoblastic MG63 cells adhered to hydrophilic (HPL) and hydrophobic surfaces. On the hydrophobic surface, less formation of focal contacts and actin stress fibers, a delay in cell cycle progression, and an increase in apoptosis were observed. By using fibroblast growth factor 1 (FGF1) as a model growth factor, we also investigated intracellular signaling pathways on hydrophilic and hydrophobic surfaces. The activation of Ras, Akt, and ERK by FGF1 was impaired in MG63 cells on the hydrophobic surface. The overexpression of constitutively active form of Ras and Akt rescued those cells from apoptosis and recovered cell cycle progression. Furthermore, their overexpression also restored the actin cytoskeletal organization on the hydrophobic surface. Finally, the proliferative, antiapoptotic, and cytoskeletal effects of constitutively active Ras in MG63 cells on the hydrophobic surface were blocked by wortmannin and PD98059 that inhibit Akt and ERK activation, respectively. Therefore, our results suggest that the activation of Ras and its downstream molecules Akt and ERK to an appropriate level is one of crucial elements in the determination of osteoblast cell responses. The Ras pathway may represent a cell biological target that should be considered for successful surface modification of biomaterials to induce adequate cell responses in the bone tissue

  19. Boundary layers of aqueous surfactant and block copolymer solutions against hydrophobic and hydrophilic solid surfaces

    International Nuclear Information System (INIS)

    Steitz, Roland; Schemmel, Sebastian; Shi Hongwei; Findenegg, Gerhard H

    2005-01-01

    The boundary layer of aqueous surfactants and amphiphilic triblock copolymers against flat solid surfaces of different degrees of hydrophobicity was investigated by neutron reflectometry (NR), grazing incidence small angle neutron scattering (GISANS) and atomic force microscopy (AFM). Solid substrates of different hydrophobicities were prepared by appropriate surface treatment or by coating silicon wafers with polymer films of different chemical natures. For substrates coated with thin films (20-30 nm) of deuterated poly(styrene) (water contact angle θ w ∼ 90), neutron reflectivity measurements on the polymer/water interface revealed a water depleted liquid boundary layer of 2-3 nm thickness and a density about 90% of the bulk water density. No pronounced depletion layer was found at the interface of water against a less hydrophobic polyelectrolyte coating (θ w ∼ 63). It is believed that the observed depletion layer at the hydrophobic polymer/water interface is a precursor of the nanobubbles which have been observed by AFM at this interface. Decoration of the polymer coatings by adsorbed layers of nonionic C m E n surfactants improves their wettability by the aqueous phase at surfactant concentrations well below the critical micellar concentration (CMC) of the surfactant. Here, GISANS experiments conducted on the system SiO 2 /C 8 E 4 /D 2 O reveal that there is no preferred lateral organization of the C 8 E 4 adsorption layers. For amphiphilic triblock copolymers (PEO-PPO-PEO) it is found that under equilibrium conditions they form solvent-swollen brushes both at the air/water and the solid/water interface. In the latter case, the brushes transform to uniform, dense layers after extensive rinsing with water and subsequent solvent evaporation. The primary adsorption layers maintain properties of the precursor brushes. In particular, their thickness scales with the number of ethylene oxide units (EO) of the block copolymer. In the case of dip-coating without

  20. Super-tough, ultra-stretchable and strongly compressive hydrogels with core-shell latex particles inducing efficient aggregation of hydrophobic chains.

    Science.gov (United States)

    Ren, Xiuyan; Huang, Chang; Duan, Lijie; Liu, Baijun; Bu, Lvjun; Guan, Shuang; Hou, Jiliang; Zhang, Huixuan; Gao, Guanghui

    2017-05-14

    Toughness, strechability and compressibility for hydrogels were ordinarily balanced for their use as mechanically responsive materials. For example, macromolecular microsphere composite hydrogels with chemical crosslinking exhibited excellent compression strength and strechability, but poor tensile stress. Here, a novel strategy for the preparation of a super-tough, ultra-stretchable and strongly compressive hydrogel was proposed by introducing core-shell latex particles (LPs) as crosslinking centers for inducing efficient aggregation of hydrophobic chains. The core-shell LPs always maintained a spherical shape due to the presence of a hard core even by an external force and the soft shell could interact with hydrophobic chains due to hydrophobic interactions. As a result, the hydrogels reinforced by core-shell LPs exhibited not only a high tensile strength of 1.8 MPa and dramatic elongation of over 20 times, but also an excellent compressive performance of 13.5 MPa at a strain of 90%. The Mullins effect was verified for the validity of core-shell LP-reinforced hydrogels by inducing aggregation of hydrophobic chains. The novel strategy strives to provide a better avenue for designing and developing a new generation of hydrophobic association tough hydrogels with excellent mechanical properties.

  1. Fabrication of large-area hydrophobic surfaces with femtosecond-laser-structured molds

    Science.gov (United States)

    Wu, P. H.; Cheng, C. W.; Chang, C. P.; Wu, T. M.; Wang, J. K.

    2011-11-01

    Fast replication of large-area femtosecond-laser-induced surface micro/nanostructures on plastic parts by injection molding is demonstrated. An STAVAX steel mold insert is irradiated by femtosecond laser pulses with linear or circular polarization to form periodic-like nanostructures or nanostructure-covered conical microstructures. It was then used for the process of thermal injection molding. The process provides high-volume manufacturing means to generate hydrophobic enhanced plastic parts, which is expected to be widely used in consumables and chemical/biomedical device industries.

  2. Numerical Simulation of Turbulent Half-corrugated Channel Flow by Hydrophilic and Hydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    M. R. Rastan

    2018-03-01

    Full Text Available In the first part of the present study, a two dimensional half-corrugated channel flow is simulated at Reynolds number of 104, in no-slip condition (hydrophilic surfaces( using various low Reynolds turbulence models as well as standard k-ε model; and an appropriate turbulence model (k-ω 1998 model( is proposed. Then, in order to evaluate the proposed solution method in simulation of flow adjacent to hydrophobic surfaces, turbulent flow is simulated in simple channel and the results are compared with the literature. Finally, two dimensional half-corrugated channel flow at Reynolds number of 104 is simulated again in vicinity of hydrophobic surfaces for varoius slip lengths. The results show that this method is capable of drag reduction in such a way that an increase of 200 μm in slip length leads to a massive drag reduction up to 38%. In addition, to access a significant drag reduction in turbulent flows, the non-dimensionalized slip length should be larger than the minimum.

  3. The interaction between fluid flow and ultra-hydrophobic surface in mini channel

    Directory of Open Access Journals (Sweden)

    Jasikova Darina

    2017-01-01

    Full Text Available Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 × 8 × 8 mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH. There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application.

  4. Effect of micropatterning induced surface hydrophobicity on drug release from electrospun cellulose acetate nanofibers

    Science.gov (United States)

    Adepu, Shivakalyani; Gaydhane, Mrunalini K.; Kakunuri, Manohar; Sharma, Chandra S.; Khandelwal, Mudrika; Eichhorn, Stephen J.

    2017-12-01

    Sustained release and prevention of burst release for low half-life drugs like Diclofenac sodium is crucial to prevent drug related toxicity. Electrospun nanofibers have emerged recently as potential carrier materials for controlled and sustained drug release. Here, we present a facile method to prevent burst release by tuning the surface wettability through template assisted micropatterning of drug loaded electrospun cellulose acetate (CA) nanofibers. A known amount of drug (Diclofenac sodium) was first mixed with CA and then electrospun in the form of a nanofabric. This as-spun network was hydrophilic in nature. However, when electrospinning was carried out through non-conducting templates, viz nylon meshes with 50 and 100 μm size openings, two kinds of hydrophobic micro-patterned CA nanofabrics were produced. In vitro transdermal testing of our nanofibrous mats was carried out; these tests were able to show that it would be possible to create a patch for transdermal drug release. Further, our results show that with optimized micro-patterned dimensions, a zero order sustained drug release of up to 12 h may be achieved for the transdermal system when compared to non-patterned samples. This patterning caused a change in the surface wettability, to a hydrophobic surface, resulting in a controlled diffusion of the hydrophilic drug. Patterning assisted in controlling the initial burst release, which is a significant finding especially for low half-life drugs.

  5. Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity

    Directory of Open Access Journals (Sweden)

    Adewale Adewuyi

    2017-09-01

    Full Text Available Cellulose (SC isolated from sesame seed (SS was surface modified with the introduction of an ester functional group via a simple reaction to produce the modified product (SA. SS, SC and SA were characterized using Fourier transform infrared (FTIR, X-ray diffraction (XRD, thermogravimetric analysis (TG, particle size distribution (PSD, zeta potential and scanning electron microscopy (SEM. SC and SA were evaluated for their water holding capacity (WC, oil holding capacity (OC, swelling capacity (SW and their ability to adsorb heavy metals. The FTIR revealed peaks corresponding to the formation of the ester functional group at the surface of SA. The crystallinity of SC was 28.02% but after the modification, it increased to 77.03% in SA. The PSD of SC and SA was both monomodal with sizes of 10.1305 μm in SC and 10.2511 μm in SA. The adsorption capacity of SC towards Pb (II and Cu (II ions was higher than that of SA. However, SA was unable to adsorb Cu (II ions. SA exhibited the lower WC and SW values as compared to SC which suggested an improved hydrophobicity after the modification. This study has shown that hydrophobicity can be improved in cellulose via surface modification.

  6. Mode pattern of internal flow in a water droplet on a vibrating hydrophobic surface.

    Science.gov (United States)

    Kim, Hun; Lim, Hee-Chang

    2015-06-04

    The objective of this study is to understand the mode pattern of the internal flow in a water droplet placed on a hydrophobic surface that periodically and vertically vibrates. As a result, a water droplet on a vibrating hydrophobic surface has a typical shape that depends on each resonance mode, and, additionally, we observed a diversified lobe size and internal flows in the water droplet. The size of each lobe at the resonance frequency was relatively greater than that at the neighboring frequencies, and the internal flow of the nth order mode was also observed in the flow visualization. In general, large symmetrical flow streams were generated along the vertical axis in each mode, with a large circulating movement from the bottom to the top, and then to the triple contact line along the droplet surface. In contrast, modes 2 and 4 generated a Y-shaped flow pattern, in which the flow moved to the node point in the lower part of the droplet, but modes 6 and 8 had similar patterns, with only a little difference. In addition, as a result of the PIV measurement, while the flow velocity of mode 4 was faster than that of model 2, those of modes 6 and 8 were almost similar.

  7. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  8. 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.

  9. Adsorption behavior of a human monoclonal antibody at hydrophilic and hydrophobic surfaces

    Science.gov (United States)

    Couston, Ruairidh G.; Skoda, Maximilian W.; Uddin, Shahid; van der Walle, Christopher F.

    2013-01-01

    One aspiration for the formulation of human monoclonal antibodies (mAb) is to reach high solution concentrations without compromising stability. Protein surface activity leading to instability is well known, but our understanding of mAb adsorption to the solid-liquid interface in relevant pH and surfactant conditions is incomplete. To investigate these conditions, we used total internal reflection fluorescence (TIRF) and neutron reflectometry (NR). The mAb tested (“mAb-1”) showed highest surface loading to silica at pH 7.4 (~12 mg/m2), with lower surface loading at pH 5.5 (~5.5 mg/m2, further from its pI of 8.99) and to hydrophobized silica (~2 mg/m2). The extent of desorption of mAb-1 from silica or hydrophobized silica was related to the relative affinity of polysorbate 20 or 80 for the same surface. mAb-1 adsorbed to silica on co-injection with polysorbate (above its critical micelle concentration) and also to silica pre-coated with polysorbate. A bilayer model was developed from NR data for mAb-1 at concentrations of 50–5000 mg/L, pH 5.5, and 50–2000 mg/L, pH 7.4. The inner mAb-1 layer was adsorbed to the SiO2 surface at near saturation with an end-on” orientation, while the outer mAb-1 layer was sparse and molecules had a “side-on” orientation. A non-uniform triple layer was observed at 5000 mg/L, pH 7.4, suggesting mAb-1 adsorbed to the SiO2 surface as oligomers at this concentration and pH. mAb-1 adsorbed as a sparse monolayer to hydrophobized silica, with a layer thickness increasing with bulk concentration - suggesting a near end-on orientation without observable relaxation-unfolding. PMID:23196810

  10. Influence of absorbed moisture on surface hydrophobization of ethanol pretreated and plasma treated ramie fibers

    International Nuclear Information System (INIS)

    Zhou Zhou; Wang Jilong; Huang Xiao; Zhang Liwen; Moyo, Senelisile; Sun Shiyuan; Qiu Yiping

    2012-01-01

    The existence of moisture in the substrate material may influence the effect of atmospheric pressure plasma treatment. Our previous study has found that the employment of ethanol pretreatment and plasma treatment can effectively induce hydrophobic surface modification of cellulose fiber to enhance the compatibility to polypropylene (PP) matrix, and this study aims to investigate the influence of fiber moisture regain on the treatment effect of this technique. Ramie fibers with three different moisture regains (MR) (2.5, 6.1 and 23.5%) are pretreated with ethanol followed by atmospheric pressure plasma treatment. Scanning electron microscope (SEM) shows that the 2.5% MR group has the most significant plasma etching effect. X-ray photoelectron spectroscopy (XPS) analysis indicates an increase of C-C and a decrease of C-O bond in the plasma treated groups, and the largest raise of C-C bond for the 2.5% MR group. The water contact angles of the 2.5 and 6.1% MR groups increase, whereas no significant change is showed in the 23.5% MR group. The interfacial shear strengths (IFSS) measured by microbond pull-out test are raised by 44 and 25% when moisture regains are 2.5 and 6.1%, while presented no apparent improvement at high moisture regain of 23.5%. Therefore, it can be concluded that moisture regain has negative influence on the surface hydrophobization of ramie fibers in the improvement of adhesion property to PP matrix.

  11. Durable Lotus-effect surfaces with hierarchical structure using micro- and nanosized hydrophobic silica particles.

    Science.gov (United States)

    Ebert, Daniel; Bhushan, Bharat

    2012-02-15

    Surfaces with a very high apparent water contact angle (CA) and low water contact angle hysteresis (CAH) exhibit many useful characteristics, among them extreme water repellency, low drag for fluid flow, and a self-cleaning effect. The leaf of the Lotus plant (Nelumbo nucifera) achieves these properties using a hierarchical structure with roughness on both the micro- and nanoscale. It is of great interest to create durable surfaces with the so-called "Lotus effect" for many important applications. In this study, hierarchically structured surfaces with Lotus-effect properties were fabricated using micro- and nanosized hydrophobic silica particles and a simple spray method. In addition, hierarchically structured surfaces were prepared by spraying a nanoparticulate coating over a micropatterned surface. To examine the similarities between surfaces using microparticles versus a uniform micropattern as the microstructure, CA and CAH were compared across a range of pitch values for the two types of microstructures. Wear experiments were performed using an atomic force microscope (AFM), a ball-on-flat tribometer, and a water jet apparatus to verify multiscale wear resistance. These surfaces have potential uses in engineering applications requiring Lotus-effect properties and high durability. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. Comparison of SF6 and CF4 Plasma Treatment for Surface Hydrophobization of PET Polymer

    Directory of Open Access Journals (Sweden)

    Matic Resnik

    2018-02-01

    Full Text Available The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF6 and CF4 gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF6 plasma, was explained by the electronegativity of both gases.

  13. Relation between acid back-diffusion and luminal surface hydrophobicity in canine gastric mucosa: Effects of salicylate and prostaglandin

    International Nuclear Information System (INIS)

    Goddard, P.J.

    1989-01-01

    The stomach is thought to be protected from luminal acid by a gastric mucosal barrier that restricts the diffusion of acid into tissue. This study tested the hypothesis that the hydrophobic luminal surface of canine gastric mucosa incubated in Ussing chambers, impedes the back-diffusion of luminal acid into the tissue. Isolated sheets of mucosa were treated with cimetidine to inhibit spontaneous acid secretion, and incubated under conditions that prevented significant secretion of luminal bicarbonate. By measuring acid loss from the luminal compartment using the pH-stat technique, acid back-diffusion was continuously monitored; potential difference (PD) was measured as an index of tissue viability. Tissue luminal surface hydrophobicity was estimated by contact angle analysis at the end of each experiment. Addition of 16,16-dimethyl prostaglandin E 2 to the nutrient compartment enhanced luminal surface hydrophobicity, but did not reduce acid back-diffusion in tissues that maintained a constant PD. 10 mM salicylate at pH 4.00 in the luminal compartment reduced surface hydrophobicity, but this decrease did not occur if 1 ug/ml prostaglandin was present in the nutrient solution. Despite possessing relatively hydrophilic and relatively hydrophobic surface properties, respectively, acid back-diffusion in the absence of salicylate was not significantly different between these two groups. Neither group maintained a PD after incubation with salicylate. Lastly, radiolabeled salicylate was used to calculate the free (non-salicylate associated) acid loss in tissues incubated with salicylate and/or prostaglandin. No significant correlation was found between free acid back-diffusion and luminal surface hydrophobicity. These data do not support the hypothesis that acid back-diffusion in impeded by the hydrophobic surface presented by isolated canine gastric mucosa

  14. Pining phenomena of an evaporated droplet on the hydrophobic micro-textured surfaces

    International Nuclear Information System (INIS)

    Yu, Dong In; Doh, Seung Woo; Park, Hyun Sun; Moriyama Kiyofumia; Kim, Moo Hwan; Kwak, Ho Jae; Ahn, Ho Seon

    2015-01-01

    When the decreased contact angle reaches the receding contact angle, the contact radius is reduced while maintaining a constant contact angle, i.e., this evaporation mode is known as the constant contact angle (CCA) mode. The emphasis of the droplet evaporation is that the transition from CCR to CCA modes is relative with the rate of the droplet evaporation, and it is markedly influenced by the surface wettability. In this study, it is focused on the evaporation mode transition. Especially, the transition from CCR to CCA modes is investigated on the hydrophobic microtextured surfaces. On the basis of the thermodynamics, the transition from CCR to CCA mode is theoretically analyzed. The thermodynamic model is developed to estimate the receding contact angle at the evaporation mode transition. Additionally, to compare between the theoretical model and experimental results, it is shown that the experimental receding contact angle is well estimated by the receding contact angle with the theoretical model. This study was performed to investigate the pinning phenomena of an evaporated droplet on the hydrophobic micro-textured surfaces. The pinning phenomena at the contact line were shown theoretically to be due to the most favorable thermodynamics process that caused the Gibbs free energy to rapidly reach an equilibrium state during droplet evaporation. The evaporation mode underwent a transition when the decrease in the Gibbs free energy was equivalent for the CCR and CCA modes. On the basis of the analysis described here, a theoretical model was developed to estimate the receding contact angle at the mode transition as a function of the surface conditions

  15. Surface hydrophobic co-modification of hollow silica nanoparticles toward large-area transparent superhydrophobic coatings.

    Science.gov (United States)

    Gao, Liangjuan; He, Junhui

    2013-04-15

    The present paper reports a novel, simple, and efficient approach to fabricate transparent superhydrophobic coatings on glass substrates by spray-coating stearic acid (STA) and 1H,1H,2H,2H-perflurooctyltriethoxysilane (POTS) co-modified hollow silica nanoparticles (SPHSNs), the surfaces of which were hydrophobic. The surface wettability of coatings was dependent on the conditions of post-treatment: the water contact angle of coating increased and then leveled off with increase in either the drying temperature or the drying time. When the coating was treated at 150°C for 5h, the water contact angle was as high as 160° and the sliding angle was lower than 1°, reaching excellent superhydrophobicity. They remained 159° and ≤1°, respectively, even after 3months storage under indoor conditions (20°C, 20%RH), demonstrating the long time stability of coating superhydrophobicity. The coating was robust both to the impact of water droplets (297 cm/s) and to acidic (pH=1) and basic (pH=14) droplets. It showed good transparency in the visible-near infrared spectral range, and the maximum transmittance reached as high as 89%. Fourier transform infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis were used to investigate the interactions among STA, POTS, and hollow silica nanoparticles (HSNs). Scanning electron microscopy and atomic force microscopy were used to observe and estimate the morphology and surface roughness of coatings. Optical properties were characterized by a UV-visible-near infrared spectrophotometer. Surface wettability was studied by a contact angle/interface system. The enhancement of hydrophobicity to superhydrophobicity by post-treatment was discussed based on the transition from the Wenzel state to the Cassie state. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Relationship between Surface Properties and In Vitro Drug Release from Compressed Matrix Containing Polymeric Materials with Different Hydrophobicity Degrees

    Directory of Open Access Journals (Sweden)

    Cristhian J. Yarce

    2017-01-01

    Full Text Available This work is the continuation of a study focused on establishing relations between surface thermodynamic properties and in vitro release mechanisms using a model drug (ampicillin trihydrate, besides analyzing the granulometric properties of new polymeric materials and thus establishing the potential to be used in the pharmaceutical field as modified delivery excipients. To do this, we used copolymeric materials derived from maleic anhydride with decreasing polarity corresponding to poly(isobutylene-alt-maleic acid (hydrophilic, sodium salt of poly(maleic acid-alt-octadecene (amphiphilic, poly(maleic anhydride-alt-octadecene (hydrophobic and the reference polymer hydroxyl-propyl-methyl-cellulose (HPMC. Each material alone and in blends underwent spectroscopic characterization by FTIR, thermal characterization by DSC and granulometric characterization using flow and compaction tests. Each tablet was prepared at different polymer ratios of 0%, 10%, 20%, 30% and 40%, and the surface properties were determined, including the roughness by micro-visualization, contact angle and water absorption rate by the sessile drop method and obtaining Wadh and surface free energy (SFE using the semi-empirical models of Young–Dupré and  Owens-Wendt-Rabel-Käelbe (OWRK, respectively. Dissolution profiles were determined simulating physiological conditions in vitro, where the kinetic models of order-zero, order-one, Higuchi and Korsmeyer–Peppas were evaluated. The results showed a strong relationship between the proportion and nature of the polymer to the surface thermodynamic properties and kinetic release mechanism.

  17. From Beetles in Nature to the Laboratory: Actuating Underwater Locomotion on Hydrophobic Surfaces.

    Science.gov (United States)

    Pinchasik, Bat-El; Steinkühler, Jan; Wuytens, Pieter; Skirtach, Andre G; Fratzl, Peter; Möhwald, Helmuth

    2015-12-29

    The controlled wetting and dewetting of surfaces is a primary mechanism used by beetles in nature, such as the ladybird and the leaf beetle for underwater locomotion.1 Their adhesion to surfaces underwater is enabled through the attachment of bubbles trapped in their setae-covered legs. Locomotion, however, is performed by applying mechanical forces in order to move, attach, and detach the bubbles in a controlled manner. Under synthetic conditions, however, when a bubble is bound to a surface, it is nearly impossible to maneuver without the use of external stimuli. Thus, actuated wetting and dewetting of surfaces remain challenges. Here, electrowetting-on-dielectric (EWOD) is used for the manipulation of bubble-particle complexes on unpatterned surfaces. Bubbles nucleate on catalytic Janus disks adjacent to a hydrophobic surface. By changing the wettability of the surface through electrowetting, the bubbles show a variety of reactions, depending on the shape and periodicity of the electrical signal. Time-resolved (μs) imaging of bubble radial oscillations reveals possible mechanisms for the lateral mobility of bubbles on a surface under electrowetting: bubble instability is induced when electric pulses are carefully adjusted. This instability is used to control the surface-bound bubble locomotion and is described in terms of the change in surface energy. It is shown that a deterministic force applied normal can lead to a random walk of micrometer-sized bubbles by exploiting the phenomenon of contact angle hysteresis. Finally, bubble use in nature for underwater locomotion and the actuated bubble locomotion presented in this study are compared.

  18. Hydrophobicity-driven self-assembly of protein and silver nanoparticles for protein detection using surface-enhanced Raman scattering.

    Science.gov (United States)

    Kahraman, Mehmet; Balz, Ben N; Wachsmann-Hogiu, Sebastian

    2013-05-21

    Surface-enhanced Raman scattering (SERS) is a promising analytical technique for the detection and characterization of biological molecules and structures. The role of hydrophobic and hydrophilic surfaces in the self-assembly of protein-metallic nanoparticle structures for label-free protein detection is demonstrated. Aggregation is driven by both the hydrophobicity of the surface as well as the charge of the proteins. The best conditions for obtaining a reproducible SERS signal that allows for sensitive, label-free protein detection are provided by the use of hydrophobic surfaces and 16 × 10(11) NPs per mL. A detection limit of approximately 0.5 μg mL(-1) is achieved regardless of the proteins' charge properties and size. The developed method is simple and can be used for reproducible and sensitive detection and characterization of a wide variety of biological molecules and various structures with different sizes and charge status.

  19. Evaporation Flux Distribution of Drops on a Hydrophilic or Hydrophobic Flat Surface by Molecular Simulations.

    Science.gov (United States)

    Xie, Chiyu; Liu, Guangzhi; Wang, Moran

    2016-08-16

    The evaporation flux distribution of sessile drops is investigated by molecular dynamic simulations. Three evaporating modes are classified, including the diffusion dominant mode, the substrate heating mode, and the environment heating mode. Both hydrophilic and hydrophobic drop-substrate interactions are considered. To count the evaporation flux distribution, which is position dependent, we proposed an azimuthal-angle-based division method under the assumption of spherical crown shape of drops. The modeling results show that the edge evaporation, i.e., near the contact line, is enhanced for hydrophilic drops in all the three modes. The surface diffusion of liquid molecular absorbed on solid substrate for hydrophilic cases plays an important role as well as the space diffusion on the enhanced evaporation rate at the edge. For hydrophobic drops, the edge evaporation flux is higher for the substrate heating mode, but lower than elsewhere of the drop for the diffusion dominant mode; however, a nearly uniform distribution is found for the environment heating mode. The evidence shows that the temperature distribution inside drops plays a key role in the position-dependent evaporation flux.

  20. Hydrophobic thiol-ene surfaces fabricated via plasma activation and photo polymerization

    Science.gov (United States)

    Champathet, P.; Ervithayasuporn, V.; Osotchan, T.; Dangtip, S.

    2017-09-01

    Alumina, such as glazed alumina for electrical insulator, operated in an open field subjects to a very harsh condition; resulting in lifetime shortening. Coating hydrophobic layer on alumina surface can help prolonging its lifetime. In this study, 25 ×25 mm alumina sheets were used as substrates. The hydrophobic composite polymers were prepared from (3-mercaptopropyl)trimethoxysilane(MPTMS), 2,4,6,8-tetramethyl-2,4,6,8tetravinylcyclotetra siloxane(TMTVSi), pentaerythritoltetra(3-mercaptopropionate)(PETMP), 2,2-dimethoxy-2-phe nylaceto phenone(photoinitiator) and heptadecafluorodecylmethacrylate(HEFDMA) via the thiol-ene reaction. The alumina sheets were first activated by dielectric-barrier discharge plasma to improve its adhesion. All the polymers were found to optimize at the ratio of (MPTMS:TMTVSi:PETMP:HDFDMA) to 4:2:1:2 for coating on the alumina substrate. To enhance polymerization, 2,2-dimethoxy-2-phenylaceto phenome was also used as a photoinitiator A proper mixing sequence in the thiol-ene reaction results in film with excellent surface retention after prolong soaking in solvent such as acetone. FTIR shows that S-H and C=C functional groups have significantly changed after photopolymerization and thermally cured. The static contact angle increase from mere 53.0°±1.5° of the uncoated substrate to 120.0°±1.2° after coating. SEM shows the film with clear appearance of a few-micron thick. Under AFM, the coated surface roughness was about 9.3 nm with evenly distributed spikes of a few nanometer in height. The cross-cut test also confirmed the film was very smooth and none of the square of the films detached.

  1. Robust superhydrophobic silicon without a low surface-energy hydrophobic coating.

    Science.gov (United States)

    Hoshian, Sasha; Jokinen, Ville; Somerkivi, Villeseveri; Lokanathan, Arcot R; Franssila, Sami

    2015-01-14

    Superhydrophobic surfaces without low surface-energy (hydrophobic) modification such as silanization or (fluoro)polymer coatings are crucial for water-repellent applications that need to survive under harsh UV or IR exposures and mechanical abrasion. In this work, robust low-hysteresis superhydrophobic surfaces are demonstrated using a novel hierarchical silicon structure without a low surface-energy coating. The proposed geometry produces superhydrophobicity out of silicon that is naturally hydrophilic. The structure is composed of collapsed silicon nanowires on top and bottom of T-shaped micropillars. Collapsed silicon nanowires cause superhydrophobicity due to nanoscale air pockets trapped below them. T-shaped micropillars significantly decrease the water contact angle hysteresis because microscale air pockets are trapped between them and can not easily escape. Robustness is studied under mechanical polishing, high-energy photoexposure, high temperature, high-pressure water shower, and different acidic and solvent environments. Mechanical abrasion damages the nanowires on top of micropillars, but those at the bottom survive. Small increase of hysteresis is seen, but the surface is still superhydrophobic after abrasion.

  2. Formation of hydrophobic coating on glass surface using atmospheric pressure non-thermal plasma in ambient air

    International Nuclear Information System (INIS)

    Fang, Z; Qiu, Y; Kuffel, E

    2004-01-01

    Non-thermal plasmas under atmospheric pressure are of great interest in material surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of a glass surface for improving hydrophobicity using a non-thermal plasma generated by a dielectric barrier corona discharge (DBCD) with a needle array-to-plane electrode arrangement in atmospheric air is conducted, and the surface properties of the glass before and after the DBCD treatment are studied using contact angle measurement, surface resistance measurement and the wet flashover voltage test. The effects of the plasma dose (the product of average discharge power and treatment time) of DBCD on the surface modification are studied, and the mechanism of interaction between the plasma and glass surface is discussed. It is found that a layer of hydrophobic coating is formed on the glass surface through DBCD treatment, and the improvement of hydrophobicity depends on the plasma dose of the DBCD. It seems that there is an optimum plasma dose for the surface treatment. The test results of thermal ageing and chemical ageing show that the hydrophobic layer has quite stable characteristics

  3. An experimental study on the effects of rough hydrophobic surfaces on the flow around a circular cylinder

    Science.gov (United States)

    Kim, Nayoung; Kim, Hyunseok; Park, Hyungmin

    2015-08-01

    The present study investigates the effect that rough hydrophobic (or superhydrophobic) surfaces have on the flow separation and subsequent vortex structures in a turbulent wake behind a circular cylinder. The velocity fields were measured using two-dimensional particle image velocimetry in a water tunnel with Reynolds numbers of 0.7-2.3 × 104. The spray-coating of hydrophobic nanoparticles and roughened Teflon was used to produce the rough hydrophobic surfaces, and sandpapers with two different grit sizes were used to sand the Teflon into streamwise and spanwise directions, respectively, in order to examine the effect of the slip direction. The rough hydrophobic surface was found to enhance the turbulence in the flows above the circular cylinder and along the separating shear layers, resulting in a delay of the flow separation and early vortex roll-up in the wake. As a result, the size of the recirculation bubble in the wake was reduced by up to 40%, while the drag reduction of less than 10% is estimated from a wake survey. However, these effects are reversed as the Reynolds number increases. The surface texture normal to the flow direction (spanwise slip) was found to be more effective than that aligned to the flow (streamwise slip), supporting the suggested mechanism. In addition, the superhydrophobic surface is locally applied by varying the installation angle and that applied around the separation point is most effective, indicating that the rough hydrophobic surface directly affects the boundary layer at flow separation. In order to control the flow around a circular cylinder using rough hydrophobic surfaces, it is suggested to have a smaller roughness width, which can stably retain air pockets. In addition, a higher gas fraction and a more uniform distribution of the roughness size are helpful to enhance the performance such as the separation delay and drag reduction.

  4. Raman study of lysozyme amyloid fibrils suspended on super-hydrophobic surfaces by shear flow

    KAUST Repository

    Moretti, Manola

    2017-05-19

    The shear flow generated at the rim of a drop evaporating on a micro-fabricated super-hydrophobic surface has been used to suspend and orient single/few lysozyme amyloid fibrils between two pillars for substrate-free characterization. Micro Raman spectroscopy performed on extended fibers evidenced a shift of the Amide I band main peak to the value attributed to β-sheet secondary structure, characteristic of the amyloid fibers. In addition, given the orientation sensitivity of the anisotropic molecule, the Raman signal of the main secondary structure was nicely enhanced for a fiber alignment parallel to the polarization direction of the laser. The substrate-free sample generated by this suspending technique is suitable for other structural analysis methods, where fiber crystals are investigated. It could be further employed for generation of arrays and patterns in a controllable fashion, where bio-compatible material is needed.

  5. Impact of air and water vapor environments on the hydrophobicity of surfaces.

    Science.gov (United States)

    Weisensee, Patricia B; Neelakantan, Nitin K; Suslick, Kenneth S; Jacobi, Anthony M; King, William P

    2015-09-01

    Droplet wettability and mobility play an important role in dropwise condensation heat transfer. Heat exchangers and heat pipes operate at liquid-vapor saturation. We hypothesize that the wetting behavior of liquid water on microstructures surrounded by pure water vapor differs from that for water droplets in air. The static and dynamic contact angles and contact angle hysteresis of water droplets were measured in air and pure water vapor environments inside a pressure vessel. Pressures ranged from 60 to 1000 mbar, with corresponding saturation temperatures between 36 and 100°C. The wetting behavior was studied on four hydrophobic surfaces: flat Teflon-coated, micropillars, micro-scale meshes, and nanoparticle-coated with hierarchical micro- and nanoscale roughness. Static advancing contact angles are 9° lower in the water vapor environment than in air on a flat surface. One explanation for this reduction in contact angles is water vapor adsorption to the Teflon. On microstructured surfaces, the vapor environment has little effect on the static contact angles. In all cases, variations in pressure and temperature do not influence the wettability and mobility of the water droplets. In most cases, advancing contact angles increase and contact angle hysteresis decreases when the droplets are sliding or rolling down an inclined surface. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Synthesis of highly hydrophobic floating magnetic polymer nanocomposites for the removal of oils from water surface

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mudan, E-mail: chenmudan@163.com [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Jiang, Wei, E-mail: climentjw@126.com [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang, Fenghe [Department of Environmental Science and Engineering, Nanjing Normal University, Nanjing 210023 (China); Shen, Ping; Ma, Peichang; Gu, Junjun; Mao, Jianyu; Li, Fengsheng [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2013-12-01

    The removal of organic contaminants, particularly oil spills from water surface is of great technological importance for environmental protection. In this article, we present a novel, economic and environment-friendly core–shell composite material based on magnetic hollow Fe{sub 3}O{sub 4} nanoparticles (MNPs) that was fabricated by two-step process, which can fast and efficiently separate oils from water surface under a magnetic field. The magnetic Fe{sub 3}O{sub 4} nanoparticles (MNPs) were coated with a polystyrene layer successfully to form water-repellent and oil-absorbing surfaces, which could float on water and selectively absorb lubricating oil up to 3 times of the particles’ weight while completely repelling water. More importantly, the oils could be readily removed from the surfaces of nanocomposites by a simple treatment and the nanocomposites still kept highly hydrophobic and superoleophilic characteristics, so the nanocomposites have an excellent recyclability in the oil-absorbent capacity. Several techniques such as transmission electron microscope (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used in the characterization of the materials. In addition, magnetic force and oils removal capability tests were also performed. It will open up a potential and broad application in wastewater treatment.

  7. Synthesis of highly hydrophobic floating magnetic polymer nanocomposites for the removal of oils from water surface

    Science.gov (United States)

    Chen, Mudan; Jiang, Wei; Wang, Fenghe; Shen, Ping; Ma, Peichang; Gu, Junjun; Mao, Jianyu; Li, Fengsheng

    2013-12-01

    The removal of organic contaminants, particularly oil spills from water surface is of great technological importance for environmental protection. In this article, we present a novel, economic and environment-friendly core-shell composite material based on magnetic hollow Fe3O4 nanoparticles (MNPs) that was fabricated by two-step process, which can fast and efficiently separate oils from water surface under a magnetic field. The magnetic Fe3O4 nanoparticles (MNPs) were coated with a polystyrene layer successfully to form water-repellent and oil-absorbing surfaces, which could float on water and selectively absorb lubricating oil up to 3 times of the particles’ weight while completely repelling water. More importantly, the oils could be readily removed from the surfaces of nanocomposites by a simple treatment and the nanocomposites still kept highly hydrophobic and superoleophilic characteristics, so the nanocomposites have an excellent recyclability in the oil-absorbent capacity. Several techniques such as transmission electron microscope (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used in the characterization of the materials. In addition, magnetic force and oils removal capability tests were also performed. It will open up a potential and broad application in wastewater treatment.

  8. Oil and gas pipelines with hydrophobic surfaces better equipped to deal with gas hydrate flow assurance issues

    DEFF Research Database (Denmark)

    Perfeldt, Christine Malmos; Sharifi, Hassan; von Solms, Nicolas

    2015-01-01

    Gas hydrate deposition can cause plugging in oil and gas pipelines with resultant flow assurance challenges. Presently, the energy industry uses chemical additives in order to manage hydrate formation, however these chemicals are expensive and may be associated with safety and environmental...... crystallizer. This indicates that 10 to 14 times less KHI is needed in the presence of a hydrophobically coated surface. These experimental studies suggest that the use of hydrophobic surfaces or pipelines could serve as an alternative or additional flow assurance approach for gas hydration mitigation...... and management....

  9. Sol-gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings.

    Science.gov (United States)

    Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Murali, Adhigan; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2012-02-01

    Sol-gel silica/nanoclay composites were prepared through sol-gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K(+) and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si-O-Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38°C. From DSC thermograms, we observed that the ΔH value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2θ=8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Simultaneous Dropwise and Filmwise Condensation on a Microstructured Surface without the Assistance of a Hydrophobic Coating

    Science.gov (United States)

    Orejon, Daniel; Shardt, Orest; Kumar Gunda, Naga Siva; Ikuta, Tatsuya; Takahashi, Koji; Mitra, Sushanta K.; Takata, Yasuyuki

    2017-11-01

    We demonstrate micropillar surfaces on which condensation occurs in a new mode with simultaneous dropwise/filmwise condensation (DWC/FWC). This is achieved without the assistance of a hydrophobic coating; the pillars and base surface are hydrophilic. By considering thermodynamic principles of droplet wetting and spreading, we designed microstructured surfaces where the condensate is able to spread through the structures. The geometry of the microstructures constrains the condensate between the pillars, the rise of condensate above the structures is not thermodynamically favorable and condensation takes place as FWC between pillars. At the same time, the continuous nucleation, growth and departure of droplets at the pillars' tops in a DWC fashion is observed. We propose a simple resistance based heat transfer model to support the greater heat transfer performance of the simultaneous DWC/FWC when compared to solely FWC. In addition we propose rational guidelines for the design of an optimum configuration that maximizes the heat transfer performance in the simultaneous DWC/FWC mode. The authors acknowledge the support of WPI-I2CNER and KAKENHI JSPS.

  11. Puddle jumping: Spontaneous ejection of large liquid droplets from hydrophobic surfaces during drop tower tests

    Science.gov (United States)

    Attari, B.; Weislogel, M.; Wollman, A.; Chen, Y.; Snyder, T.

    2016-10-01

    Large droplets and puddles jump spontaneously from sufficiently hydrophobic surfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 104 times larger than their normal terrestrial counterparts. We provide and/or confirm quick and qualitative design guides for such "drop shooters" as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, and fluid properties including contact angle. The latter is determined via profile image comparisons with numerical equilibrium interface computations. Water drop volumes of 0.04-400 ml at ejection speeds of -0.007-0.12 m/s are demonstrated herein. A sample application of the drop jump method is made to the classic problem of low-gravity phase change heat transfer for large impinging drops. Many other candidate problems might be identified by the reader.

  12. The hydrophilic-to-hydrophobic transition in glassy silica is driven by the atomic topology of its surface

    Science.gov (United States)

    Yu, Yingtian; Krishnan, N. M. Anoop; Smedskjaer, Morten M.; Sant, Gaurav; Bauchy, Mathieu

    2018-02-01

    The surface reactivity and hydrophilicity of silicate materials are key properties for various industrial applications. However, the structural origin of their affinity for water remains unclear. Here, based on reactive molecular dynamics simulations of a series of artificial glassy silica surfaces annealed at various temperatures and subsequently exposed to water, we show that silica exhibits a hydrophilic-to-hydrophobic transition driven by its silanol surface density. By applying topological constraint theory, we show that the surface reactivity and hydrophilic/hydrophobic character of silica are controlled by the atomic topology of its surface. This suggests that novel silicate materials with tailored reactivity and hydrophilicity could be developed through the topological nanoengineering of their surface.

  13. Construction of hydrophobic wood surfaces by room temperature deposition of rutile (TiO2) nanostructures

    Science.gov (United States)

    Zheng, Rongbo; Tshabalala, Mandla A.; Li, Qingyu; Wang, Hongyan

    2015-02-01

    A convenient room temperature approach was developed for growing rutile TiO2 hierarchical structures on the wood surface by direct hydrolysis and crystallization of TiCl3 in saturated NaCl aqueous solution. The morphology and the crystal structure of TiO2 coated on the wood surface were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The TiO2 morphology on the wood surface could be tuned by simply changing either the reaction time or pH value of the reaction mixture. After modification with perfluorodecyltriethoxysilane (PFDTS), the water contact angle (WCA) of the TiO2-treated wood (T1) surface increased to 140.0 ± 4.2°, which indicated a highly hydrophobic wood surface. In addition, compared with untreated control wood, PFDTS-TiO2 treatment (PFDTS-T1-treated) not only reduced liquid water uptake, but also delayed the onset of water saturation point of the wood substrate. The weight change of PFDTS-T1-treated wood after 24 h of water immersion was 19.3%, compared to 81.3% for the untreated control wood. After 867 h of water immersion, the weight change for the treated and untreated wood specimens was 117.1%, and 155.1%, respectively. The untreated control wood reached the steady state after 187 h, while the PFDTS-T1-treated wood did not reach the steady state until after 600 h of immersion.

  14. The Influence of New Hydrophobic Silica Nanoparticles on the Surface Properties of the Films Obtained from Bilayer Hybrids

    Directory of Open Access Journals (Sweden)

    Cristian Petcu

    2017-02-01

    Full Text Available Ultra-hydrophobic bilayer coatings on a glass surface were fabricated by sol–gel process using hexadecyltrimethoxysilane (C16TMS and tetramethoxysilane (TMOS (1:4 molar ratio as precursors. After coating, silica nanoparticles (SiO2 NPs functionalized with different mono-alkoxy derivatives (methoxytrimethylsilane, TMeMS; ethoxydimethylvinylsilane, DMeVES; ethoxydimethylphenylsilane, DMePhES; and methoxydimethyloctylsilane, DMeC8MS were added, assuring the microscale roughness on the glass surface. Influences of the functionalized SiO2 NPs and surface morphology on the hydrophobicity of the hybrid films were discussed. The successful functionalization of SiO2 NPs with hydrophobic alkyl groups were confirmed by Fourier transform infrared spectroscopy (FTIR. The thermal stability of hydrophobic SiO2 NPs showed that the degradation of the alkyl groups takes place in the 200–400 °C range. Bilayer coating with C16TMS/TMOS and SiO2 NPs modified with alkoxysilane substituted with C8 alkyl chain (SiO2 NP-C8 has micro/nano structure. Hydrophobicity of functionalized SiO2 NPs-C8 and its higher degree of nanometer-scale roughness gave rise to ultra-hydrophobicity performance for bilayer coating C16TMS/TMOS + SiO2 NPs-C8 (145°, compared to other similar hybrid structures. Our synthesis method for the functionalization of SiO2 NPs is useful for the modification of surface polarity and roughness.

  15. Surface modification of hydrophobic polymers for improvement of endothelial cell-surface interactions

    NARCIS (Netherlands)

    Dekker, A.; Dekker, A.; Reitsma, K.; Beugeling, T.; Beugeling, T.; Bantjes, A.; Bantjes, A.; Feijen, Jan; Kirkpatrick, C.J.; van Aken, W.G.

    1992-01-01

    The aim of this study is to improve the interaction of endothelial cells with polymers used in vascular prostheses. Polytetrafluoroethylene (PTFE; Teflon) films were treated by means of nitrogen and oxygen plasmas. Depending on the plasma exposure time, modified PTFE surfaces showed water-contact

  16. Fabrication of Super Hydrophobic Surfaces by fs Laser Pulses : How to Produce Self-Cleaning Surfaces

    NARCIS (Netherlands)

    Groenendijk, M.N.W.

    2008-01-01

    The chair of Applied Laser Technology of the University of Twente, The Netherlands, is performing research into applications of ultrashort pulsed lasers for micromachining. In a recent project, PhD student Max Groenendijk developed a method for the production of super water repellant surfaces by

  17. The five Ws (and one H) of super-hydrophobic surfaces in medicine

    KAUST Repository

    Gentile, F.

    2014-05-05

    Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W), are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule. 2014 by the authors; licensee MDPI, Basel, Switzerland.

  18. The Five Ws (and one H of Super-Hydrophobic Surfaces in Medicine

    Directory of Open Access Journals (Sweden)

    Francesco Gentile

    2014-05-01

    Full Text Available Super-hydrophobic surfaces (SHSs are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W, are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule.

  19. Internal flow and evaporation characteristic inside a water droplet on a vertical vibrating hydrophobic surface

    International Nuclear Information System (INIS)

    Kim Hun; Lim, Hee Chang

    2015-01-01

    This study aims to understand the internal flow and the evaporation characteristics of a deionized water droplet subjected to vertical forced vibrations. To predict and evaluate its resonance frequency, the theories of Lamb, Strani, and Sabetta have been applied. To visualize the precise mode, shape, and internal flow inside a droplet, the experiment utilizes a combination of a high-speed camera, macro lens, and continuous laser. As a result, a water droplet on a hydrophobic surface has its typical shape at each mode, and complicated vortices are observed inside the droplet. In particular, large symmetrical flow streams are generated along the vertical axis at each mode, with a large circulating movement from the bottom to the top and then to the triple contact line along the droplet surface. In addition, a bifurcation-shaped flow pattern is formed at modes 2 and 4, whereas a large ellipsoid-shape flow pattern forms at modes 6 and 8. Mode 4 has the fastest internal flow speed and evaporation rate, followed by modes 8 then 6, with 2 having the slowest of these properties. Each mode has the fastest evaporation rate amongst its neighboring frequencies. Finally, the droplet evaporation under vertical vibration would lead to more rapid evaporation, particularly for mode 4

  20. A bioluminescence ATP assay for estimating surface hydrophobicity and membrane damage of Escherichia coli cells treated with pulsed electric fields

    Science.gov (United States)

    Pulse Electric Field (PEF) treatments, a non-thermal process have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (AJ, pH 3.8) purchased from a wholesale ...

  1. Prediction of protein retention times in hydrophobic interaction chromatography by robust statistical characterization of their atomic-level surface properties.

    Science.gov (United States)

    Hanke, Alexander T; Klijn, Marieke E; Verhaert, Peter D E M; van der Wielen, Luuk A M; Ottens, Marcel; Eppink, Michel H M; van de Sandt, Emile J A X

    2016-03-01

    The correlation between the dimensionless retention times (DRT) of proteins in hydrophobic interaction chromatography (HIC) and their surface properties were investigated. A ternary atomic-level hydrophobicity scale was used to calculate the distribution of local average hydrophobicity across the proteins surfaces. These distributions were characterized by robust descriptive statistics to reduce their sensitivity to small changes in the three-dimensional structure. The applicability of these statistics for the prediction of protein retention behaviour was looked into. A linear combination of robust statistics describing the central tendency, heterogeneity and frequency of highly hydrophobic clusters was found to have a good predictive capability (R2  = 0.78), when combined a factor to account for protein size differences. The achieved error of prediction was 35% lower than for a similar model based on a description of the protein surface on an amino acid level. This indicates that a robust and mathematically simple model based on an atomic description of the protein surface can be used for the prediction of the retention behaviour of conformationally stable globular proteins with a well determined 3D structure in HIC. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:372-381, 2016. © 2016 American Institute of Chemical Engineers.

  2. Interactions between nano-TiO{sub 2} and the oral cavity: Impact of nanomaterial surface hydrophilicity/hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Teubl, Birgit J.; Schimpel, Christa [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Leitinger, Gerd [Institute of Cell Biology, Histology and Embryology, Research Unit Electron Microscopic Techniques, Medical University of Graz, 8010 (Austria); Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Bauer, Bettina [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Fröhlich, Eleonore [Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Zimmer, Andreas [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Roblegg, Eva, E-mail: eva.roblegg@uni-graz.at [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria)

    2015-04-09

    Highlights: • Hydrophilic as well as hydrophobic TiO{sub 2} NPs agglomerated under oral physiological conditions. • Particles penetrated the upper and lower buccal epithelium, independent on the degree of hydrophilicity. • Most of the hydrophobic particles were found in vesicular structures, while hydrophilic particles were freely distributed in the cytoplasm. • Hydrophilic particles had a higher potential to trigger toxic effects (e.g., ROS) than hydrophobic particles. - Abstract: Titanium dioxide (TiO{sub 2}) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle–cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO{sub 2} particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species.

  3. Fabrication of a silver-ragwort-leaf-like super-hydrophobic micro/nanoporous fibrous mat surface by electrospinning

    International Nuclear Information System (INIS)

    Miyauchi, Yasuhiro; Ding, Bin; Shiratori, Seimei

    2006-01-01

    Inspired by the self-cleaning silver ragwort leaf, we have recently fabricated a biomimetic super-hydrophobic fibrous mat surface comprising micro/nanoporous polystyrene (PS) microfibres via electrospinning. The rough surface of the silver ragwort leaf fibres, with nanometre-sized grooves along the fibre axis, was imitated by forming micro- and nanostructured pores on the electrospun fibre surface. The solvent composition ratios of tetrahydrofuran (THF) to N,N-dimethylformamide (DMF) in PS solutions were proved to be the key parameter to affect the fibre surface structures due to the various phase separation speeds of the solvents from PS fibres during electrospinning. The combination of the hierarchical surface roughness inherent in electrospun microfibrous PS mats and the low surface free energy of PS yielded a stable super-hydrophobicity with water contact angles as high as 159.5 0 for a 12 mg water droplet, exceeding that (147 0 ) of the silver ragwort leaf. Moreover, the hydrophobicity of the porous PS mat surface was found to increase on increasing the surface roughness of the microfibres

  4. Effects of biosurfactants, mannosylerythritol lipids, on the hydrophobicity of solid surfaces and infection behaviours of plant pathogenic fungi.

    Science.gov (United States)

    Yoshida, S; Koitabashi, M; Nakamura, J; Fukuoka, T; Sakai, H; Abe, M; Kitamoto, D; Kitamoto, H

    2015-07-01

    To investigate the effects of mannosylerythritol lipids (MELs) on the hydrophobicity of solid surfaces, their suppressive activity against the early infection behaviours of several phytopathogenic fungal conidia, and their suppressive activity against disease occurrences on fungal host plant leaves. The changes in the hydrophobicity of plastic film surfaces resulting from treatments with MEL solutions (MEL-A, MEL-B, MEL-C and isoMEL-B) and synthetic surfactant solutions were evaluated based on the changes in contact angles of water droplets placed on the surfaces. The droplet angles on surfaces treated with MELs were verified to decrease within 100 s after placement, with contact angles similar to those observed on Tween 20-treated surfaces, indicating decreases in surface hydrophobicity after MEL treatments. Next, conidial germination, germ tube elongation and the formation of appressorium of Blumeria graminis f. sp. tritici, Colletotrichum dematium, Glomerella cingulata and Magnaporthe grisea were evaluated on plastic surfaces that were pretreated with surfactant solutions. On the surfaces of MEL-treated plastic film, inhibition of conidial germination, germ tube elongation, and suppression of appressoria formation tended to be observed, although the level of effect was dependent on the combination of fungal species and type of MEL. Inoculation tests revealed that the powdery mildew symptom caused by B. graminis f. sp. tritici was significantly suppressed on wheat leaf segments treated with MELs. MELs exhibited superior abilities in reducing the hydrophobicity of solid surfaces, and have the potential to suppress powdery mildew in wheat plants, presumably due to the inhibition of conidial germination. This study provides significant evidence of the potential for MELs to be used as novel agricultural chemical pesticides. © 2015 The Society for Applied Microbiology.

  5. Nisin-activated hydrophobic and hydrophilic surfaces: assessment of peptide adsorption and antibacterial activity against some food pathogens.

    Science.gov (United States)

    Karam, Layal; Jama, Charafeddine; Mamede, Anne-Sophie; Boukla, Samir; Dhulster, Pascal; Chihib, Nour-Eddine

    2013-12-01

    An effective antimicrobial packaging or food contact surface should be able to kill or inhibit micro-organisms that cause food-borne illnesses. Setting up such systems, by nisin adsorption on hydrophilic and hydrophobic surfaces, is still a matter of debate. For this purpose, nisin was adsorbed on two types of low-density polyethylene: the hydrophobic native film and the hydrophilic acrylic acid-treated surface. The antibacterial activity was compared for those two films and it was highly dependent on the nature of the surface and the nisin-adsorbed amount. The hydrophilic surfaces presented higher antibacterial activity and higher amount of nisin than the hydrophobic surfaces. The effectiveness of the activated surfaces was assessed against Listeria innocua and the food pathogens Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus. S. aureus was more sensitive than the three other test bacteria toward both nisin-functionalized films. Simulation tests to mimic refrigerated temperature showed that the films were effective at 20 and 4 °C with no significant difference between the two temperatures after 30 min of exposure to culture media.

  6. Synthesis of sponge-like hydrophobic NiBi{sub 3} surface by 200 keV Ar ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Siva, Vantari; Datta, D.P. [School of Physical Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050 (India); Chatterjee, S. [Colloids and Materials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Acharya Vihar, Bhubaneswar 751 013 (India); Varma, S. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050 (India)

    2017-07-15

    Highlights: • A sponge-like hydrophobic NiBi{sub 3} surface has been synthesized using 200 keV Ar ion implantation. • A competition between amorphization and re-crystallization was observed in the existing phases owing to comparable magnitudes of nuclear and electronic energy depositions. • The relation between hydrophobic nature and sponge-like NiBi{sub 3} phase seems interesting, which is attributed to ion beam induced sputtering and mixing of the layers. - Abstract: Sponge-like nanostructures develop under Ar-ion implantation of a Ni–Bi bilayer with increasing ion fluence at room temperature. The surface morphology features different stages of evolution as a function of ion fluence, finally resulting in a planar surface at the highest fluence. Our investigations on the chemical composition reveal a spontaneous formation of NiBi{sub 3} phase on the surface of the as deposited bilayer film. Interestingly, we observe a competition between crystallization and amorphization of the existing poly-crystalline phases as a function of the implanted fluence. Measurements of contact angle by sessile drop method clearly show the ion-fluence dependent hydrophobic nature of the nano-structured surfaces. The wettability has been correlated with the variation in roughness and composition of the implanted surface. In fact, our experimental results confirm dominant effect of ion-sputtering as well as ion-induced mixing at the bilayer interface in the evolution of the sponge-like surface.

  7. Preparation of hydrophobic polyvinyl alcohol aerogel via the surface modification of boron nitride for environmental remediation

    Science.gov (United States)

    Zhang, Ruiyang; Wan, Wenchao; Qiu, Lijuan; Wang, Yonghua; Zhou, Ying

    2017-10-01

    Macroscopic polyvinyl alcohol (PVA) aerogel is of great interest in environmental remediation due to its low cost and easy fabrication. However, the hydrophily of PVA aerogel limited its application in oil-water separation. In this work, boron nitride (BN)-modified PVA aerogel has been successfully prepared by a cost-effective frozen-drying method. PVA plays a role as a scaffold of aerogel to support BN nanosheets which can modify the surface properties of PVA aerogel, resulting in a dramatic change of wettability from hydrophily (0°) to hydrophobicity (94.9°-100.8°). Moreover, the obtained BN-modified PVA aerogel possesses a favorable porous structure, low density (41.8-60.0 mg/cm3) and good adsorption capacity (12-38 g/g), which make it a promising wastewater treatment material. Importantly, PVA aerogel with other functions can be easily fabricated through coupling with other inorganic materials by this strategy, which can provide various promising applications for environmental remediation.

  8. Colloid properties of hydrophobic modified alginate: Surface tension, ζ-potential, viscosity and emulsification.

    Science.gov (United States)

    Wu, Zongmei; Wu, Jie; Zhang, Ruling; Yuan, Shichao; Lu, Qingliang; Yu, Yueqin

    2018-02-01

    Micelle properties of hydrophobic modified alginate (HM-alginate) in various dispersion media have been studied by surface tension, ζ-potential, and viscosity measurements. Effect of salt on micelle properties showed that the presence of counter ion weakened the repulsive interaction between surfactant ions, decreased the critical micelle concentration (CMC) value of the HM-alginate, reduced the effective volume dimensions of HM-alginate and hence viscosity, which coincide with the corresponding ζ-potential values. Soy oil-in-water emulsions, stabilized solely by HM-alginate, were produced in high speed homogenization conditions and their stability properties were studied by visual inspection, optical microscopy and droplet size measurements. The results showed that emulsions (oil-water ratio was 1:7) containing 15mg/mL HM-alginate presented better stability during 15days storage, which stating clearly that HM-alginate is an effective emulsifier to stabilize oil-in-water emulsions. The herein presented homogeneous method for preparation of emulsion has the potential to be used in food industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Superhydrophobic cotton fabrics prepared by sol–gel coating of TiO2 and surface hydrophobization

    Directory of Open Access Journals (Sweden)

    Chao-Hua Xue et al

    2008-01-01

    Full Text Available By coating fibers with titania sol to generate a dual-size surface roughness, followed by hydrophobization with stearic acid, 1H,1H,2H,2H-perfluorodecyltrichlorosilane or their combination, hydrophilic cotton fabrics were made superhydrophobic. The surface wettability and topology of cotton fabrics were studied by contact angle measurement and scanning electron microscopy. The UV-shielding property of the treated fabrics was also characterized by UV-vis spectrophotometry.

  10. Elaboration of highly hydrophobic polymeric surface — a potential strategy to reduce the adhesion of pathogenic bacteria?

    Energy Technology Data Exchange (ETDEWEB)

    Poncin-Epaillard, F., E-mail: fabienne.poncin-epaillard@univ-lemans.fr [Institut des Molécules et Matériaux du Mans (IMMM), département Polymères, Colloïdes et Interfaces, UMR CNRS 6283 Université LUNAM, av. O. Messiaen, 72085 Le Mans (France); Herry, J.M. [INRA-AgroParisTech, UMR 1319 MICALIS, équipe B2HM, 25 avenue de la République, 91300 Massy (France); Marmey, P.; Legeay, G. [CTTM, 20 rue Thalès de Milet 72000 Le Mans (France); Debarnot, D. [Institut des Molécules et Matériaux du Mans (IMMM), département Polymères, Colloïdes et Interfaces, UMR CNRS 6283 Université LUNAM, av. O. Messiaen, 72085 Le Mans (France); Bellon-Fontaine, M.N. [INRA-AgroParisTech, UMR 1319 MICALIS, équipe B2HM, 25 avenue de la République, 91300 Massy (France)

    2013-04-01

    Different polymeric surfaces have been modified in order to reach a high hydrophobic character, indeed the superhydrophobicity property. For this purpose, polypropylene and polystyrene have been treated by RF or μwaves CF{sub 4} plasma with different volumes, the results were compared according to the density of injected power. The effect of pretreatment such as mechanical abrasion or plasma activation was also studied. The modified surfaces were shown as hydrophobic, or even superhydrophobic depending of defects density. They were characterized by measurement of wettability and roughness at different scales, i.e. macroscopic, mesoscopic and atomic. It has been shown that a homogeneous surface at the macroscopic scale could be heterogeneous at lower mesoscopic scale. This was associated with the crystallinity of the material. The bioadhesion tests were performed with Gram positive and negative pathogenic strains: Listeria monocytogenes, Pseudomonas aeruginosa and Hafnia alvei. They have demonstrated an antibacterial efficiency of very hydrophobic and amorphous PS treated for all strains tested and a strain-dependent efficiency with modified PP surface being very heterogeneous at the mesoscopic scale. Thus, these biological results pointed out not only the respective role of the surface chemistry and topography in bacterial adhesion, but also the dependence on the peaks and valley distribution at bacteria dimension scale. Highlights: ► Simple, eco-friendly modification of polymers leading to highly hydrophobic property ► Plasma treatment inducing surface fluorination and roughness ► Study of non-adhesion of different types of bacteria onto such polymeric surfaces ► Dependence of their non-adhesion on surface topography whatever their characteristics.

  11. Preparation of enhanced hydrophobic poly(L-lactide-co-ε-caprolactone) films surface and its blood compatibility

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung Il; Lim, Jin Ik; Jung, Youngmee; Mun, Cho Hay [Division of Life and Health Science, Biomaterials Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Kim, Ji Heung, E-mail: kimjh@skku.edu [Department of Chemical Engineering, Polymer Technology Institute, Sungkyunkwan University, Suwon, Kyunggi (Korea, Republic of); Kim, Soo Hyun, E-mail: soohkim@kist.re.kr [Division of Life and Health Science, Biomaterials Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul (Korea, Republic of)

    2013-07-01

    Hydrophobicity-enhanced poly(L-lactide-co-ε-caprolactone) (PLCL) (50:50) films were cast by using the solvent–nonsolvent casting method. PLCL (50:50) was synthesized by the well-known random copolymerization process and confirmed by {sup 1}H NMR analysis. The molecular weight of the synthesized PLCL was measured by gel permeation chromatography (GPC). Number-average (Mn), weight-average (Mw) molecular weights and polydispersity (Mw/Mn) were 7 × 10{sup 4}, 1.2 × 10{sup 5}, and 1.7, respectively. PLCL films were cast in vacuum condition with various nonsolvents and nonsolvent ratios. Tetrahydrofuran (THF) was used as the solvent and three different alcohols were used as the nonsolvent: methanol, ethanol, and isopropyl alcohol (IPA). Surface hydrophobicity was confirmed by water contact angle. The water contact angle was increased from 81° ± 2° to 107° ± 2°. Water contact angle was influenced by surface porosity and topography. The prepared film surfaces were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The change of crystalline property was characterized by X-ray diffraction (XRD). Platelet adhesion tests on the modified PLCL film surfaces were evaluated by platelet-rich plasma (PRP). The modified film surface exhibited enhanced hydrophobicity and reduced platelet adhesion ratio depending on the surface topography. One of the candidate products proposed as a potential blood compatible material showed a markedly reduced platelet adhesion property.

  12. Synthesis and Characterization of Surface Modified, Fluorescent and Biocompatible ZnS Nanoparticles with a Hydrophobic Chitosan Derivative.

    Science.gov (United States)

    Jothimani, B; Sureshkumar, S; Venkatachalapathy, B

    2017-07-01

    The introduction of a hydrophobic moiety on chitosan enhances the self-assembling properties, mucoadhesion, the permeability of the macromolecule and aids in target specific delivery. Our group synthesized a hydrophobic trans N-(6,6-Dimethyl-2-hepten-4-ynyl)chitosan derivative (CSD) and studied the surface modification of ZnS nanoparticles in a single pot reaction. X-ray diffraction studies and FESEM imaging confirms the nano size and morphology of the surface modified Zinc sulfide nanoparticles (ZnS-CSD NPs). The proposed ZnS-CSD NPs showed excellent emission at 457 nm. Photostability studies indicate that the surface modified ZnS-CSD NPs possess better photostability than Rhodamine B and FITC. Cell viability tests confirmed the biocompatibility of the modified nanoparticles. All these features of ZnS- CSD NPs makes these candidates an excellent choice in a wide range of in vitro or in vivo studies as fluorescent biological labels.

  13. The effects of non-solvent on surface morphology and hydrophobicity of dip-coated polypropylene membrane

    Science.gov (United States)

    Faiqotul Himma, Nurul; Kusuma Wardani, Anita; Gede Wenten, I.

    2017-05-01

    Polypropylene (PP) has been widely used for fabrication of hydrophobic microporous membrane due to its good thermal and chemical stability. However, the hydrophobicity of PP is inadequate to prevent membrane wetting which hinders its application in long-term operation of membrane contactor and other hydrophobic membrane processes. Endowing the membrane with superhydrophobicity has become an attractive way to improve wetting resistance. In this work, superhydrophobic PP membrane was prepared by coating with roughened polymer film. A simple technique of two-step dip-coating was used for deposition of the non-solvent solution and polymer solution. The effects of five non-solvent types were investigated, including ethanol, isopropyl alcohol (IPA), acetone, methyl ethyl ketone (MEK), and cyclohexanone. All non-solvents increased the surface roughness, leading to an improvement of membrane hydrophobicity. Superhydrophobic PP membranes with high water contact angle (WCA) of 150.4° and 151.3° have been successfully prepared by using IPA and MEK, respectively. Morphology characterization revealed that both modified membranes had more uniform and larger number of smaller aggregates which might minimize surface area in contact with liquid, resulting in increased contact angle. As the coating was conducted separately, the utilization of non-solvent could be more effective.

  14. Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

    Science.gov (United States)

    Chen, Weimin; Zhou, Xiaoyan; Zhang, Xiaotao; Bian, Jie; Shi, Shukai; Nguyen, Thiphuong; Chen, Minzhi; Wan, Jinglin

    2017-06-01

    The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and Sisbnd Osbnd C. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

  15. In Vitro Effects of Plantago Major Extract, Aucubin, and Baicalein on Candida albicans Biofilm Formation, Metabolic Activity, and Cell Surface Hydrophobicity.

    Science.gov (United States)

    Shirley, Karina Pezo; Windsor, L Jack; Eckert, George J; Gregory, Richard L

    2017-08-01

    To determine the in vitro effectiveness of Plantago major extract, along with two of its active components, aucubin and baicalein, on the inhibition of Candida albicans growth, biofilm formation, metabolic activity, and cell surface hydrophobicity. Twofold dilutions of P. major, aucubin, and baicalein were used to determine the minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and the minimum biofilm inhibitory concentration (MBIC) of each solution. Separately, twofold dilutions of P. major, aucubin, and baicalein were used to determine the metabolic activity of established C. albicans biofilm using a 2,3-bis (2- methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-carboxanilide reduction assay. Twofold dilutions of P. major, aucubin, and baicalein were used to determine the cell surface hydrophobicity of treated C. albicans biofilm by a two-phase assay using hexadecane. The hydrophobicity percentage of the cell surface was then calculated. A mixed-model ANOVA test was used for intergroup comparisons. The MICs of P. major extract (diluted 1:2 to 1:8), aucubin (61 to 244 μg/ml), and baicalein (0.0063 to 100 μg/ml) on the total growth of C. albicans were noticeable at their highest concentrations, and the inhibition was dose dependent. The MFC was evaluated after 48 hours of incubation, and aucubin (244 μg/ml) exhibited a strong fungicidal activity at its highest concentration against C. albicans growth. The MBIC indicated no growth or reduced growth of C. albicans biofilm at the highest concentrations of aucubin (61 to 244 μg/ml) and baicalein (25 to 100 μg/ml). Similarly, the effects of these reagents on C. albicans biofilm metabolic activity and hydrophobicity demonstrated high effectiveness at their highest concentrations. P. major extract, aucubin, and baicalein caused a dose-dependent reduction on the total growth, biofilm formation, metabolic activity, and cell surface hydrophobicity of C. albicans. This demonstrates their

  16. Surface hydrophobicity and acidity effect on alumina catalyst in catalytic methanol dehydration reaction.

    Science.gov (United States)

    Osman, Ahmed I; Abu-Dahrieh, Jehad K; Rooney, David W; Thompson, Jillian; Halawy, Samih A; Mohamed, Mohamed A

    2017-12-01

    Methanol to dimethyl ether (MTD) is considered one of the main routes for the production of clean bio-fuel. The effect of copper loading on the catalytic performance of different phases of alumina that formed by calcination at two different temperatures was examined for the dehydration of methanol to dimethyl ether (DME). A range of Cu loadings of (1, 2, 4, 6, 10 and 15% Cu wt/wt) on Al 2 O 3 calcined at 350 and 550 °C were prepared and characterized by TGA, XRD, BET, NH 3 -TPD, TEM, H 2 -TPR, SEM, EDX, XPS and DRIFT-Pyridine techniques. The prepared catalysts were used in a fixed bed reactor under reaction conditions in which the temperature ranged from 180-300 °C with weight hourly space velocity (WHSV) = 12.1 h -1 . It was observed that all catalysts calcined at 550 °C (γ-Al 2 O 3 support phase) exhibited higher activity than those calcined at 350 °C (γ-AlOOH), and this is due to the phase support change. Furthermore, the optimum Cu loading was found to be 6% Cu/γ-Al 2 O 3 with this catalyst also showing a high degree of stability under steady state conditions and this is attributed to the enhancement in surface acidity and hydrophobicity. The addition of copper to the support improved the catalyst properties and activity. For all the copper modified catalysts, the optimum catalyst with high degree of activity and stability was 6% copper loaded on gamma alumina. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  17. Hydrophobic dielectric surface influenced active layer thickness effect on hysteresis and mobility degradation in organic field effect transistors

    Science.gov (United States)

    Padma, N.

    2016-02-01

    Effect of active layer thickness, influenced by the hydrophobic dielectric surface, on the performance of copper phthalocyanine based organic field effect transistors (OFETs) was studied. While charge carrier mobility was found to be highest for an optimum thickness of 30 nm, hysteresis and threshold voltage shift were found to be minimum for 15 nm thick film which is attributed to the excess availability of photogenerated carriers, especially close to the dielectric/semiconductor interface, as this thickness is within the exciton quenching length in organic semiconductors. But prolonged bias stress resulted in larger decay in drain current for higher thickness indicating the dominant role played by the larger grain boundary density in the increased volume. These results were found to be different from that on unmodified SiO2 dielectric with higher surface energy and were suggested to be caused by the 3D growth mode of CuPc films on the hydrophobic surface. Mobility degradation at higher gate voltages also exhibited a dependence on the active layer thickness which was tuned by the hydrophobic surface induced growth mode at the dielectric/semiconductor interface.

  18. Facile fabrication of hydrophobic surfaces on mechanically alloyed-Mg/HA/TiO{sub 2}/MgO bionanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Khalajabadi, Shahrouz Zamani [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Abdul Kadir, Mohammed Rafiq, E-mail: rafiq@biomedical.utm.my [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Izman, Sudin; Mohd Yusop, Mohd Zamri [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)

    2015-01-01

    Highlights: • Mg/HA/TiO{sub 2}-based nanocomposite was produced using mechanical alloying. • The hydrophobic surface coverage was fabricated on the mechanical alloyed samples by annealing. • The morphological characteristics, phase evolution and wettability of nanocomposites and the hydrophobic surface coverage were investigated. • The activation energies and reaction kinetic of the powder mixture of nanocomposites were calculated. - Abstract: The effect of mechanical alloying and post-annealing on the phase evolution, microstructure, wettability and thermal stability of Mg–HA–TiO{sub 2}–MgO composites was investigated in this study. Phase evolution and microstructure analysis were performed using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy, as well as the wettability determined by contact angle measurements with SBF. The 16-h mechanical alloying resulted in the formation of MgTiO{sub 3}, CaTiO{sub 3}, Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} phases and a decrease in wettability of the nanocomposites. A hydrophobic film with hierarchical structures comprising nanoflakes of MgTiO{sub 3}, nano-cuboids of CaTiO{sub 3}, microspheres of Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} was successfully constructed on the surface of the Mg-based nanocomposites substrates as a result of the post-annealing process. After 1-h annealing at 630 °C, the synthesized hydrophobic surface on the nanocomposite substrates decreased the wettability, as the 8-h-mechanically alloyed samples exhibited a contact angle close to 93°. The formation activation energies and reaction kinetics of the powder mixture were investigated using differential thermal analysis and thermal gravimetric analysis. The released heat, weight loss percentage and reaction kinetics increased, while the formation activation energies of the exothermic reactions decreased following an increase in the milling time.

  19. Influence of impurities and contact scale on the lubricating properties of bovine submaxillary mucin (BSM) films on a hydrophobic surface

    DEFF Research Database (Denmark)

    Nikogeorgos, Nikolaos; Madsen, Jan Busk; Lee, Seunghwan

    2014-01-01

    Lubricating properties of bovine submaxillary mucin (BSM) on a compliant, hydrophobic surface were studied as influenced by impurities, in particular bovine serum albumin (BSA), at macro and nanoscale contacts by means of pin-on-disk tribometry and friction force microscopy (FFM), respectively...... on the underlying substrates, and thus induced higher friction forces compared to the sliding contact on bare substrates.© 2014 Elsevier B.V. All rights reserved...

  20. Interactions between nano-TiO2 and the oral cavity: impact of nanomaterial surface hydrophilicity/hydrophobicity.

    Science.gov (United States)

    Teubl, Birgit J; Schimpel, Christa; Leitinger, Gerd; Bauer, Bettina; Fröhlich, Eleonore; Zimmer, Andreas; Roblegg, Eva

    2015-04-09

    Titanium dioxide (TiO2) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle-cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO2 particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Modeling of Hydrophobic Surfaces by the Stokes Problem With the Stick–Slip Boundary Conditions

    Czech Academy of Sciences Publication Activity Database

    Kučera, R.; Šátek, V.; Haslinger, Jaroslav; Fialová, S.; Pochylý, F.

    2017-01-01

    Roč. 139, č. 1 (2017), č. článku 011202. ISSN 0098-2202 Institutional support: RVO:68145535 Keywords : algebra * boundary conditions * hydrophobicity * Lagrange multipliers * Navier Stokes equations Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 1.437, year: 2016 http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleid=2536532

  2. Super-hydrophilicity to super-hydrophobicity transition of a surface with Ni micro-nano cones array

    Science.gov (United States)

    Geng, Wenyan; Hu, Anmin; Li, Ming

    2012-12-01

    A surface with Ni micro-nano cones array (MCA) was fabricated with electro-deposition method and exhibited super-hydrophilic nature when freshly prepared. Spontaneous transition from super-hydrophilicity to super-hydrophobicity was observed when the surface was exposed in air at room temperature. The special surface structure of MCA played an important role in amplifying the surface wettability. Since the surface structure remained the same as the freshly prepared Ni MCA films during the storage, the transition was proved to be attributed to the change of surface chemical composition. Such wettability transition property of Ni MCA films might shed light on the high-tech areas of self-cleaners, anti-corrosion materials, anti-contamination materials, etc.

  3. Effect of low-concentration rhamnolipid on transport of Pseudomonas aeruginosa ATCC 9027 in an ideal porous medium with hydrophilic or hydrophobic surfaces.

    Science.gov (United States)

    Zhong, Hua; Liu, Guansheng; Jiang, Yongbing; Brusseau, Mark L; Liu, Zhifeng; Liu, Yang; Zeng, Guangming

    2016-03-01

    The success of effective bioaugmentation processes for remediation of soil and groundwater contamination requires effective transport of the injected microorganisms in the subsurface environment. In this study, the effect of low concentrations of monorhamnolipid biosurfactant solutions on transport of Pseudomonas aeruginosa in an ideal porous medium (glass beads) with hydrophilic or hydrophobic surfaces was investigated by conducting miscible-displacement experiments. Transport behavior was examined for both glucose-grown and hexadecane-grown cells, with low and high surface hydrophobicity, respectively. A clean-bed colloid deposition model was used for determination of deposition rate coefficients. Results show that cells with high surface hydrophobicity exhibit greater retention than cells with low surface hydrophobicity. Rhamnolipid affects cell transport primarily by changing cell surface hydrophobicity, with an additional minor effect by increasing solution ionic strength. There is a good linear relation between k and rhamnolipid-regulated cell surface hydrophobicity presented as bacterial-adhesion-to-hydrocarbon (BATH) rate of cells (R(2)=0.71). The results of this study show the importance of hydrophobic interaction for transport of bacterial cells in silica-based porous media, and the potential of using low-concentration rhamnolipid solutions for facilitating bacterial transport in bioaugmentation efforts. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Temperature distribution of a water droplet moving on a heated super-hydrophobic surface under the icing condition

    Science.gov (United States)

    Yamazaki, Masafumi; Sumino, Yutaka; Morita, Katsuaki

    2017-11-01

    In the aviation industry, ice accretion on the airfoil has been a hazardous issue since it greatly declines the aerodynamic performance. Electric heaters and bleed air, which utilizes a part of gas emissions from engines, are used to prevent the icing. Nowadays, a new de-icing system combining electric heaters and super hydrophobic coatings have been developed to reduce the energy consumption. In the system, the heating temperature and the coating area need to be adjusted. Otherwise, the heater excessively consumes energy when it is set too high and when the coating area is not properly located, water droplets which are once dissolved possibly adhere again to the rear part of the airfoil as runback ice In order to deal with these problems, the physical phenomena of water droplets on the hydrophobic surface demand to be figured out. However, not many investigations focused on the behavior of droplets under the icing condition have been conducted. In this research, the temperature profiling of the rolling droplet on a heated super-hydrophobic surface is experimentally observed by the dual luminescent imaging.

  5. Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

    International Nuclear Information System (INIS)

    Chen, Weimin; Zhou, Xiaoyan; Zhang, Xiaotao; Bian, Jie; Shi, Shukai; Nguyen, Thiphuong; Chen, Minzhi; Wan, Jinglin

    2017-01-01

    Highlights: • Plasma working under low pressure is easy to realize industrialization. • Enhancing process finished within 75 s. • Plasma treatment leads to the increase in equilibrium contact angle by 330%. • Tinfoil film with simple chemical structure was used to reveal the mechanism. - Abstract: The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and Si−O−C. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

  6. Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weimin [College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037 (China); Jiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials, Nanjing 210037 (China); Nanjing Suman Plasma Technology Co., Ltd, Enterprise of Graduate Research Station of Jiangsu Province, No. 3 Youyihe Road, Nanjing 210001 (China); Zhou, Xiaoyan, E-mail: zhouxiaoyan@njfu.edu.cn [College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037 (China); Jiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials, Nanjing 210037 (China); Zhang, Xiaotao [College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037 (China); Jiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials, Nanjing 210037 (China); Bian, Jie [Nanjing Suman Plasma Technology Co., Ltd, Enterprise of Graduate Research Station of Jiangsu Province, No. 3 Youyihe Road, Nanjing 210001 (China); Shi, Shukai; Nguyen, Thiphuong; Chen, Minzhi [College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037 (China); Jiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials, Nanjing 210037 (China); Wan, Jinglin [Nanjing Suman Plasma Technology Co., Ltd, Enterprise of Graduate Research Station of Jiangsu Province, No. 3 Youyihe Road, Nanjing 210001 (China)

    2017-06-15

    Highlights: • Plasma working under low pressure is easy to realize industrialization. • Enhancing process finished within 75 s. • Plasma treatment leads to the increase in equilibrium contact angle by 330%. • Tinfoil film with simple chemical structure was used to reveal the mechanism. - Abstract: The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and Si−O−C. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

  7. Optimum design of amphiphilic polymers bearing hydrophobic groups for both cell surface ligand presentation and intercellular cross-linking.

    Science.gov (United States)

    Takeo, Masafumi; Li, Cuicui; Matsuda, Masayoshi; Nagai, Hiroko; Hatanaka, Wataru; Yamamoto, Tatsuhiro; Kishimura, Akihiro; Mori, Takeshi; Katayama, Yoshiki

    2015-01-01

    Amphiphilic polymers bearing hydrophobic alkyl groups are expected to be applicable for both ligand presentation on the cell surface and intercellular crosslinking. To explore the optimum design for each application, we synthesized eight different acyl-modified dextrans with varying molecular weight, alkyl length, and alkyl modification degree. We found that the behenate-modified polymers retained on the cell surface longer than the palmitate-modified ones. Since the polymers were also modified with biotin, streptavidin can be presented on the cell surface through biotin-streptavidin recognition. The duration of streptavidin on the cell surface is longer in the behenate-modified polymer than the palmitate-modified one. As for the intercellular crosslinking, the palmitate-modified polymers were more efficient than the behenate-modified polymers. The findings in this research will be helpful to design the acyl-modified polymers for the cell surface engineering.

  8. Hydrophobic ZnO-TiO2 Nanocomposite with Photocatalytic Promoting Self-Cleaning Surface

    Directory of Open Access Journals (Sweden)

    Qiang Wei

    2015-01-01

    Full Text Available The hydrophobicity and self-cleaning are the important influence factors on the precision and environment resistance of quartz crystal microbalance (QCM in detecting organic gas molecules. In this paper, ZnO nanorod array is prepared via the in situ method on the QCM coated with Au film via hydrothermal process. ZnO nanorod array film on QCM is modified by β-CD in hydrothermal process and then decorated by TiO2 after being impregnated in P25 suspension. The results show that as-prepared ZnO-TiO2 nanocomposite exhibits excellent hydrophobicity for water molecules and superior self-cleaning property for organic molecules under UV irradiation.

  9. Overexpression of NRPS4 leads to increased surface hydrophobicity in Fusarium graminearum

    DEFF Research Database (Denmark)

    Hansen, Frederik Teilfeldt; Droce, Aida; Sørensen, Jens Laurids

    2012-01-01

    ). Most of these are unknown as F. graminearum contains 19 NRPS encoding genes, but only 3 have been assigned products. For the first time, we use deletion and overexpression mutants to investigate the functions and product of NRPS4 in F. graminearum. Deletion of NRPS4 homologues in Alternaria...... might suggest that the peptide product of NRPS4 could be an architectural factor in the cell walls of Fusarium or an indirect regulator of hydrophobicity....

  10. Formation and Mechanism of Superhydrophobic/Hydrophobic Surfaces Made from Amphiphiles through Droplet-Mediated Evaporation-Induced Self-Assembly.

    Science.gov (United States)

    Dong, Fangyuan; Zhang, Mi; Tang, Wai-Wa; Wang, Yi

    2015-04-23

    Superhydrophobic/hydrophobic surfaces have attracted wide attention because of their broad applications in various regions, including coating, textile, packaging, electronic devices, and bioengineering. Many studies have been focused on the fabrication of superhydrophobic/hydrophobic surfaces using natural materials. In this paper, superhydrophobic/hydrophobic surfaces were formed by an amphiphilic natural protein, zein, using electrospinning. Water contact angle (WCA) and scanning electron microscopy (SEM) were used to characterize the hydrophobicity and surface morphology of the electrospun structures. The highest WCA of the zein electrospun surfaces could reach 155.5 ± 1.4°. To further understand the mechanism of superhydrophobic surface formation from amphiphiles using electrospinning, a synthetic amphiphilic polymer was selected, and also, a method similar to electrospinning, spray drying, was tried. The electrospun amphiphilic polymer surface showed a high hydrophobicity with a WCA of 141.4 ± 0.7°. WCA of the spray-dried zein surface could reach 125.3 ± 2.1°. The secondary structures of the zein in the electrospun film and cast-dried film were studied using ATR-FTIR, showing that α-helix to β-sheet transformation happened during the solvent evaporation in the cast drying process but not in the electrospinning process. A formation mechanism was proposed on the basis of the orientation of the amphiphiles during the solvent evaporation of different fabrication methods. The droplet-based or jet-based evaporation during electrospinning and spray drying led to the formation of the superhydrophobic/hydrophobic surface by the accumulation of the hydrophobic groups of the amphiphiles on the surface, while the surface-based evaporation during cast drying led to the formation of the hydrophilic surface by the accumulation of the hydrophilic groups of the amphiphiles on the surface.

  11. Temporal Changes in Extracellular Polymeric Substances on Hydrophobic and Hydrophilic Membrane Surfaces in a Submerged Membrane Bioreactor

    KAUST Repository

    Matar, Gerald Kamil

    2016-03-02

    Membrane surface hydrophilic modification has always been considered to mitigating biofouling in membrane bioreactors (MBRs). Four hollow-fiber ultrafiltration membranes (pore sizes ∼0.1 μm) differing only in hydrophobic or hydrophilic surface characteristics were operated at a permeate flux of 10 L/m2.h in the same lab-scale MBR fed with synthetic wastewater. In addition, identical membrane modules without permeate production (0 L/m2.h) were operated in the same lab-scale MBR. Membrane modules were autopsied after 1, 10, 20 and 30 days of MBR operation, and total extracellular polymeric substances (EPS) accumulated on the membranes were extracted and characterized in detail using several analytical tools, including conventional colorimetric tests (Lowry and Dubois), liquid chromatography with organic carbon detection (LC-OCD), fluorescence excitation - emission matrices (FEEM), fourier transform infrared (FTIR) and confocal laser scanning microscope (CLSM). The transmembrane pressure (TMP) quickly stabilized with higher values for the hydrophobic membranes than hydrophilic ones. The sulfonated polysulfone (SPSU) membrane had the highest negatively charged membrane surface, accumulated the least amount of foulants and displayed the lowest TMP. The same type of organic foulants developed with time on the four membranes and the composition of biopolymers shifted from protein dominance at early stages of filtration (day 1) towards polysaccharides dominance during later stages of MBR filtration. Nonmetric multidimensional scaling of LC-OCD data showed that biofilm samples clustered according to the sampling event (time) regardless of the membrane surface chemistry (hydrophobic or hydrophilic) or operating mode (with or without permeate flux). These results suggest that EPS composition may not be the dominant parameter for evaluating membrane performance and possibly other parameters such as biofilm thickness, porosity, compactness and structure should be considered

  12. A low-cost filler-dissolved process for fabricating super-hydrophobic poly(dimethylsiloxane) surfaces with either lotus or petal effect

    Science.gov (United States)

    Lin, Yung-Tsan; Chou, Jung-Hua

    2014-05-01

    A low-cost filler (salt) water-dissolved method is developed to produce large-area and flexible super-hydrophobic surfaces by using poly(dimethylsiloxane) (PDMS) material. Five levels of salt grain sizes are used to examine the filler size effect on fabricating the super-hydrophobic surfaces and on the hydrophobic mechanism involved. The results show that the surfaces fabricated using grain sizes of 53-74 and 74-104 µm exhibit the lotus effect (cell adhesion (CA) > 150° and self-adhesion (SA) 150° and high adhesion even upside-down). The super-hydrophobic characteristic is achieved mainly by the large micro rib-like structures, small micro rock-like bumps, and textures on the bump due to the fillers.

  13. Graphite intercalated polyaniline composite with superior anticorrosive and hydrophobic properties, as protective coating material on steel surfaces

    International Nuclear Information System (INIS)

    Rathnayake, R.M.N.M.; Mantilaka, M.M.M.G.P.G.; Hara, Masanori; Huang, Hsin-Hui; Wijayasinghe, H.W.M.A.C.; Yoshimura, Masamichi; Pitawala, H.M.T.G.A.

    2017-01-01

    Highlights: • In this paper, it has been utilized a novel method to prepare a new composite material of PANI/NPG graphite composite, using NPG vein graphite variety. • It is found that the composite works as an anti-corrosive coating on steel surfaces. Further, the prepared composite shows good hydrophobic ability, which is very useful in preventing corrosion on metal surfaces. • The prepared PANI/NPG composite material shows a significantly high corrosion resistance compared to alkyd resin/PANI coatings or alkyd resin coatings, on steel surfaces. - Abstract: Solid polymer composite systems are widely being used for potential technological applications in secondary energy sources and electrochromic devices. In this study, we synthesized and characterized a composite material composed of polyaniline (PANI) and natural needle platy (NPG) vein graphite. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, thermogravimetric and differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM) were used to study the structural and electrochemical properties of the prepared PANI/NPG graphite composite. XPS, FTIR, and micro-Raman analysis confirmed the existence of relevant functional groups and bonding in the prepared PANI/NPG composite material. The composite shows a very low corrosion rate, approximately 29 μm per year, and high hydrophobicity on steel surfaces, which helps to prevent the corrosion due to O 2 penetration towards the metal surface. It indicates that the composite can be used as a high potential surface coating material to anticorrosion. The specific capacitance of PANI/NPG composite is 833.3 F g −1 , which is higher than that of PANI. This synergistic electrical performance result proves the prepared PANI/NPG graphite composite as a suitable protective coating material for steel surfaces.

  14. Graphite intercalated polyaniline composite with superior anticorrosive and hydrophobic properties, as protective coating material on steel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rathnayake, R.M.N.M. [National Institute of Fundamental Studies, Kandy (Sri Lanka); Graduate School of Engineering, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Mantilaka, M.M.M.G.P.G. [Sri Lanka Institute of Nanotechnology, Nanotechnology and Science Park, Mahenwatte, Pitipana, Homagama (Sri Lanka); Hara, Masanori; Huang, Hsin-Hui [Graduate School of Engineering, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Wijayasinghe, H.W.M.A.C., E-mail: athula@ifs.ac.lk [National Institute of Fundamental Studies, Kandy (Sri Lanka); Yoshimura, Masamichi [Graduate School of Engineering, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Pitawala, H.M.T.G.A. [Department of Geology, University of Peradeniya, Peradeniya (Sri Lanka)

    2017-07-15

    Highlights: • In this paper, it has been utilized a novel method to prepare a new composite material of PANI/NPG graphite composite, using NPG vein graphite variety. • It is found that the composite works as an anti-corrosive coating on steel surfaces. Further, the prepared composite shows good hydrophobic ability, which is very useful in preventing corrosion on metal surfaces. • The prepared PANI/NPG composite material shows a significantly high corrosion resistance compared to alkyd resin/PANI coatings or alkyd resin coatings, on steel surfaces. - Abstract: Solid polymer composite systems are widely being used for potential technological applications in secondary energy sources and electrochromic devices. In this study, we synthesized and characterized a composite material composed of polyaniline (PANI) and natural needle platy (NPG) vein graphite. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, thermogravimetric and differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM) were used to study the structural and electrochemical properties of the prepared PANI/NPG graphite composite. XPS, FTIR, and micro-Raman analysis confirmed the existence of relevant functional groups and bonding in the prepared PANI/NPG composite material. The composite shows a very low corrosion rate, approximately 29 μm per year, and high hydrophobicity on steel surfaces, which helps to prevent the corrosion due to O{sub 2} penetration towards the metal surface. It indicates that the composite can be used as a high potential surface coating material to anticorrosion. The specific capacitance of PANI/NPG composite is 833.3 F g{sup −1}, which is higher than that of PANI. This synergistic electrical performance result proves the prepared PANI/NPG graphite composite as a suitable protective coating material for steel

  15. Impact of hydrophilic and hydrophobic functionalization of flat TiO2/Ti surfaces on proteins adsorption

    Science.gov (United States)

    Fabre, Héloïse; Mercier, Dimitri; Galtayries, Anouk; Portet, David; Delorme, Nicolas; Bardeau, Jean-François

    2018-02-01

    Controlling adsorption of proteins onto medical devices is a key issue for implant-related infections. As self-assembled monolayers (SAMs) on titanium oxide represent a good model to study the surface-protein interactions, TiO2 surface properties were modified by grafting bisphosphonate molecules terminated with hydrophilic poly(ethylene glycol) groups and hydrophobic perfluoropolyether ones, respectively. Characterisation of the surface chemistry and surface topography of the modified surfaces was performed using XPS and atomic force microscopy (AFM). Quartz-crystal microbalance with dissipation (QCM-D) was used to determine the mass of adsorbed proteins as well as its kinetics. Poly(ethylene glycol)-terminated SAMs were the most effective surfaces to limit the adsorption of both BSA and fibrinogen in comparison to perfluorinated-terminated SAMs and non-modified TiO2 surfaces, as expected. The adsorption was not reversible in the case of BSA, while a partial reversibility was observed with Fg, most probably due to multilayers of proteins. The grafted surfaces adsorbed about the same quantity of proteins in terms of molecules per surface area, most probably in monolayer or island-like groups of adsorbed proteins. The adsorption on pristine TiO2 reveals a more important, non-specific adsorption of proteins.

  16. Adenosine monophosphate is elevated in the bronchoalveolar lavage fluid of mice with acute respiratory toxicity induced by nanoparticles with high surface hydrophobicity.

    Science.gov (United States)

    Dailey, Lea Ann; Hernández-Prieto, Raquel; Casas-Ferreira, Ana Maria; Jones, Marie-Christine; Riffo-Vasquez, Yanira; Rodríguez-Gonzalo, Encarnación; Spina, Domenico; Jones, Stuart A; Smith, Norman W; Forbes, Ben; Page, Clive; Legido-Quigley, Cristina

    2015-02-01

    Inhaled nanomaterials present a challenge to traditional methods and understanding of respiratory toxicology. In this study, a non-targeted metabolomics approach was used to investigate relationships between nanoparticle hydrophobicity, inflammatory outcomes and the metabolic fingerprint in bronchoalveolar fluid. Measures of acute lung toxicity were assessed following single-dose intratracheal administration of nanoparticles with varying surface hydrophobicity (i.e. pegylated lipid nanocapsules, polyvinyl acetate nanoparticles and polystyrene beads; listed in order of increasing hydrophobicity). Broncho-alveolar lavage (BAL) fluid was collected from mice exposed to nanoparticles at a surface area dose of 220 cm(2) and metabolite fingerprints were acquired via ultra pressure liquid chromatography-mass spectrometry-based metabolomics. Particles with high surface hydrophobicity were pro-inflammatory. Multivariate analysis of the resultant small molecule fingerprints revealed clear discrimination between the vehicle control and polystyrene beads (p < 0.05), as well as between nanoparticles of different surface hydrophobicity (p < 0.0001). Further investigation of the metabolic fingerprints revealed that adenosine monophosphate (AMP) concentration in BAL correlated with neutrophilia (p < 0.01), CXCL1 levels (p < 0.05) and nanoparticle surface hydrophobicity (p < 0.001). Our results suggest that extracellular AMP is an intermediary metabolite involved in adenine nucleotide-regulated neutrophilic inflammation as well as tissue damage, and could potentially be used to monitor nanoparticle-induced responses in the lung following pulmonary administration.

  17. Evolution and accumulation of organic foulants on hydrophobic and hydrophilic membrane surfaces in a submerged membrane bioreactor

    KAUST Repository

    Matar, Gerald

    2015-09-07

    Membrane surface modification is attracting more attention to mitigate biofouling in membrane bioreactors (MBRs). Five membranes differing in chemistry and hydrophobic/hydrophilic potential were run in parallel in a lab-scale MBR under the same conditions. Membranes were sampled after 1, 10, 20 and 30 days of MBR operation with synthetic wastewater. Subsequently, accumulated organic foulants were characterised using several chemical analytical tools. Results showed similar development of organic foulants with time, illustrating that membrane surface chemistry did not affect the selection of specific organic foulants. Multivariate analysis showed that biofilm samples clustered according to the day of sampling. The composition of organic foulants shifted from protein-like substances towards humics and polysaccharides-like substances. We propose that to control biofouling in MBRs, one should focus less on the membrane surface chemistry.

  18. Direct measurement of colloidal interactions between polyaniline surfaces in a UV-curable coating formulation: the effect of surface hydrophilicity/hydrophobicity and resin composition.

    Science.gov (United States)

    Jafarzadeh, Shadi; Claesson, Per M; Pan, Jinshan; Thormann, Esben

    2014-02-04

    The interactions between polyaniline particles and polyaniline surfaces in polyester acrylate resin mixed with 1,6-hexanediol diacrylate monomer have been investigated using contact angle measurements and the atomic force microscopy colloidal probe technique. Polyaniline with different characteristics (hydrophilic and hydrophobic) were synthesized directly on spherical polystyrene particles of 10 μm in diameter. Surface forces were measured between core/shell structured polystyrene/polyaniline particles (and a pure polystyrene particle as reference) mounted on an atomic force microscope cantilever and a pressed pellet of either hydrophilic or hydrophobic polyaniline powders, in resins of various polymer:monomer ratios. A short-range purely repulsive interaction was observed between hydrophilic polyaniline (doped with phosphoric acid) surfaces in polyester acrylate resin. In contrast, interactions between hydrophobic polyaniline (doped with n-decyl phosphonic acid) were dominated by attractive forces, suggesting less compatibility and higher tendency for aggregation of these particles in liquid polyester acrylate compared to hydrophilic polyaniline. Both observations are in agreement with the conclusions from the interfacial energy studies performed by contact angle measurements.

  19. Drag penalty due to the asperities in the substrate of super-hydrophobic and liquid infused surfaces

    Science.gov (United States)

    Garcia Cartagena, Edgardo J.; Arenas, Isnardo; Leonardi, Stefano

    2017-11-01

    Direct numerical simulations of two superposed fluids in a turbulent channel with a textured surface made of pinnacles of random height have been performed. The viscosity ratio between the two fluids are N =μo /μi = 50 (μo and μi are the viscosities of outer and inner fluid respectively) mimicking a super-hydrophobic surface (water over air) and N=2.5 (water over heptane) resembling a liquid infused surface. Two set of simulations have been performed varying the Reynolds number, Reτ = 180 and Reτ = 390 . The interface between the two fluids is flat simulating infinite surface tension. The position of the interface between the two fluids has been varied in the vertical direction from the base of the substrate (what would be a rough wall) to the highest point of the roughness. Drag reduction is very sensitive to the position of the interface between the two fluids. Asperities above the interface induce a large form drag and diminish considerably the drag reduction. When the mean height of the surface measured from the interface in the outer fluid is greater than one wall unit, k+ > 1 , the drag increases with respect to a smooth wall. Present results provide a guideline to the accuracy required in manufacturing super-hydrophobic and liquid infused surfaces. This work was supported under ONR MURI Grants N00014-12-0875 and N00014-12- 1-0962, Program Manager Dr. Ki-Han Kim. Numerical simulations were performed on the Texas Advanced Computer Center.

  20. Six-Year Survival and Early Failure Rate of 2918 Implants with Hydrophobic and Hydrophilic Enossal Surfaces.

    Science.gov (United States)

    Gac, Olivier Le; Grunder, Ueli

    2015-02-05

    The aim of this chart review was to obtain an objective, quantitative assessment of the clinical performance of an implant line used in an implantological office setting. Implants with hydrophilic (INICELL) and hydrophobic (TST; both: Thommen Medical AG, Grenchen, Switzerland) enossal surfaces were compared and the cumulative implant survival rate was calculated. The data of 1063 patients that received 2918 implants (1337 INICELL, 1581 TST) was included. The average follow up time was 2.1 (1.1-5.4) years for INICELL and 4.5 (1.3-5.9) years for TST implants (Thommen Medical AG, Switzerland). In the reported period 7 implants with INICELL (0.5%) and 23 TST implants (1.5%) failed. This difference was statistically significant. The analysis of cases treated and followed up in a single implantological office for 6 years confirmed the very good clinical outcome that was achieved with both used implant lines. Within the limitations of this retrospective analysis, the overall early failure rate of the hydrophilic implants was significantly lower than that of hydrophobic implants. The use of hydrophilic implants allows the clinician to obtain less early failures, hence the interest of an up-to-date surface for the daily work of an implant practice.

  1. A rheological study of hydrophobic-surface-active polymer systems structuration; Etude rheologique de la structuration de systemes polymere hydrophobe-tensioactif

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, E.

    1997-01-29

    This work deals with the study of the rheology and the structuration of hydrophobic polymer and surfactant systems. The used associative polymers are acrylamide/nonyl methacrylate copolymers and the surfactant is nonionic. They are particularly used for hydrocarbons extraction techniques as drilling (drilling fluids) or wells cementation. The studied materials are first characterized by different analytic techniques. This preliminary stage of the work gives a good insight of the physico-chemical parameters of the systems. The effect of surfactant was shown by studying the variation of Newtonian viscosity as a function of surfactant concentration. This yields bell curves, whose maximum determines the critical aggregation concentration (cac). The hydrophobic effect is analysed in different polymer concentration regimes, in quasi-static conditions, and under shear. The study of the dynamic visco-elasticity of semi-dilute solutions allows to observe the effect of the hydrophobic associations on the relaxation time of the chains. The system can be described as a superposition of two networks of junctions: the network of physical entanglements and a second one formed by the hydrophobic links. Phenomena of structuration have been observed at room temperature for surfactant concentrations close to the cac. The increase of viscosity or elastic modulus can be 3 to 4 orders of magnitude. The effect of the temperature on the structure of the systems is studied as well. The rheological characterization of the Sol-Gel transition is developed and the rheological behavior of the solutions in a structured state shows a critical stress for rupture of the structure. Microscopic observations of the birefringence of the solutions display the existence of lamellar vesicles, which leads to the following assumption: the formation of big spherulites create a rigidification of the macromolecular network. (author) 190 refs.

  2. Synthesis of Environmentally Responsive Polymers by Atom Transfer Radical Polymerization: Generation of Reversible Hydrophilic and Hydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    Vikas Mittal

    2010-05-01

    Full Text Available Environmentally responsive poly(N-isopropylacrylamide brushes were grafted from the surface of polymer particles or flat surfaces in order to generate reversible hydrophilic and hydrophobic surfaces. The use of atom transfer radical polymerization was demonstrated for the grafting of polymer brushes as it allows efficient control on the amount of grafted polymer. The polymer particles were generated with or without surfactant in the emulsion polymerization and their surface could be modified with the atom transfer radical polymerization (ATRP initiator. The uniform functionalization of the surface with ATRP initiator was responsible for the uniform grafting of polymer brushes. The grafted brushes responded reversibly with changes in temperature indicating that the reversible responsive behavior could be translated to the particle surfaces. The particles were observed to adsorb and desorb protein and virus molecules by changing the temperatures below or higher than 32 °C. The initiator functionalized particles could also be adsorbed on the flat surfaces. The adsorption process also required optimization of the heat treatment conditions to form a uniform layer of the particles on the substrate. The grafted polymer brushes also responded to the changes in temperatures similar to the spherical particles studied through water droplets placed on the flat substrates.

  3. Strong surface effect on direct bulk flexoelectric response in solids

    International Nuclear Information System (INIS)

    Yurkov, A. S.; Tagantsev, A. K.

    2016-01-01

    In the framework of a continuum theory, it is shown that the direct bulk flexoelectric response of a finite sample essentially depends on the surface polarization energy, even in the thermodynamic limit where the body size tends to infinity. It is found that a modification of the surface energy can lead to a change in the polarization response by a factor of two. The origin of the effect is an electric field produced by surface dipoles induced by the strain gradient. The unexpected sensitivity of the polarization response to the surface energy in the thermodynamic limit is conditioned by the fact that the moments of the surface dipoles may scale as the body size

  4. Hydrophilic/hydrophobic surface modification impact on colloid lithography: Schottky-like defects, dislocation, and ideal distribution

    Science.gov (United States)

    Burtsev, Vasilii; Marchuk, Valentina; Kugaevskiy, Artem; Guselnikova, Olga; Elashnikov, Roman; Miliutina, Elena; Postnikov, Pavel; Svorcik, Vaclav; Lyutakov, Oleksiy

    2018-03-01

    Nano-spheres lithography is actually considered as a powerful tool to manufacture various periodic structures with a wide potential in the field of nano- and micro-fabrication. However, during self-assembling of colloid microspheres, various defects and mismatches can appear. In this work the size and quality of single-domains of closed-packed polystyrene (PS), grown up on thin Au layers modified by hydrophilic or hydrophobic functional groups via diazonium chemistry was studied. The effects of the surface modification on the quality and single-domain size of polystyrene (PS) microspheres array were investigated and discussed. Modified surfaces were characterized using the AFM and wettability tests. PS colloidal suspension was deposited using the drop evaporation method. Resulted PS microspheres array was characterized using the SEM, AFM and confocal microscopy technique.

  5. MS2 and Qβ bacteriophages reveal the contribution of surface hydrophobicity on the mobility of non-enveloped icosahedral viruses in SDS-based capillary zone electrophoresis.

    Science.gov (United States)

    Sautrey, Guillaume; Brié, Adrien; Gantzer, Christophe; Walcarius, Alain

    2018-01-01

    SDS is commonly employed as BGE additive in CZE analysis of non-enveloped icosahedral viruses. But the way by which SDS interacts with the surface of such viruses remains to date poorly known, making complicate to understand their behavior during a run. In this article, two related bacteriophages, MS2 and Qβ, are used as model to investigate the migration mechanism of non-enveloped icosahedral viruses in SDS-based CZE. Both phages are characterized by similar size and surface charge but significantly different surface hydrophobicity (Qβ > MS2, where '>' means 'more hydrophobic than'). By comparing their electrophoretic mobility in the presence or not of SDS on both sides of the CMC, we show that surface hydrophobicity of phages is a key factor influencing their mobility and that SDS-virus association is driven by hydrophobic interactions at the surface of virions. The CZE analyses of heated MS2 particles, which over-express hydrophobic domains at their surface, confirm this finding. The correlations between the present results and others from the literature suggest that the proposed mechanism might not be exclusive to the bacteriophages examined here. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction.

    Directory of Open Access Journals (Sweden)

    Ting Lu

    Full Text Available MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs.Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye could firmly bind to the surface of adherent cells (Hela and suspended cells (K562 even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it.These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results.

  7. Light transmittance of 1-piece hydrophobic acrylic intraocular lenses with surface light scattering removed from cadaver eyes.

    Science.gov (United States)

    Werner, Liliana; Morris, Caleb; Liu, Erica; Stallings, Shannon; Floyd, Anne; Ollerton, Andrew; Leishman, Lisa; Bodnar, Zachary

    2014-01-01

    To assess the potential effect of surface light scattering on light transmittance of 1-piece hydrophobic acrylic intraocular lenses (IOLs) with or without a blue-light filter. John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Experimental study. Intraocular lenses were obtained from human cadavers (49 IOLs total; 36 with blue-light filter) and from finished-goods inventory (controls). The IOLs were removed from cadaver eyes and the power and model matched to unused controls. After surface proteins were removed, the IOLs were hydrated for 24 hours at room temperature. Surface light scattering was measured with a Scheimpflug camera (EAS-1000 Anterior Segment Analysis System). Light transmittance was measured with a Lambda 35 UV/Vis spectrophotometer (single-beam configuration; RSA-PE-20 integrating sphere). Hydrated scatter values ranged from 4.8 to 202.5 computer-compatible tape (CCT) units for explanted IOLs with blue-light filter and 1.5 to 11.8 CCT units for controls; values ranged from 6.0 to 137.5 CCT units for explanted IOLs without a blue-light filter and 3.5 to 9.6 CCT units for controls. In both groups, there was a tendency toward increasing scatter values with increasing postoperative time. No differences in light transmittance were observed between explanted IOLs and controls in both groups (IOLs with blue-light filter: P=.407; IOL with no blue-light filter: P=.487; both paired t test). Although surface light scattering of explanted IOLs was significantly higher than that of controls and appeared to increase with time, no effect was observed on light transmittance of 1-piece hydrophobic acrylic IOLs with or without a blue-light filter. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  8. Microbial colonization of irradiated pathogenic yeast to catheter surfaces: Relationship between adherence, cell surface hydrophobicity, biofilm formation and antifungal susceptibility. A scanning electron microscope analysis.

    Science.gov (United States)

    Farrag, Hala Abdallah; A-Karam El-Din, Alzahraa; Mohamed El-Sayed, Zeinab Galal; Abdel-Latifissa, Soheir; Kamal, Mona Mohamed

    2015-06-01

    Technological advances such as long-term indwelling catheters have created milieu in which infections are a major complication. Thus it is essential to be able to recognize, diagnose, and treat infections occurring in immunocompromised patients. Adherence assay and quantitation of biofilms was performed by a spectrophotometric method, hydrophobicity was evaluated by adhesion to p-xylene. The minimum inhibitory concentration (MIC) of Nystatin was carried out by a well dilution method. Out of 100 bladder cancer patients, 23 pathogenic yeast isolates were identified. The samples were taken from urinary catheters and urine collected from their attached drainage bags. Pathogenic yeast identified were species of Candida, Cryptococcus, Saccharomyces, Blastoschizomyces, Trichosporn, Hansenula, Prototheca and Rhodotorula. With the exception of Rhodotorula minuta, the yeast were sensitive to the antimycotic agent (Nystatin) used before and after in vitro gamma irradiation at 24.41 Gy as measured by a disc diffusion method. All tested yeast strains were slime producers and showed positive adherence reactions. There were considerable differences in adherence measurements after irradiation. An increase in adherence measurement values (using a spectrophotometric method) after irradiation were detected in four strains whereas eight other strains showed a reduction in their adherence reaction. The cell surface hydrophobicity (CSH) was evaluated by adhesion to p-xylene. Candida tropicalis showed a hydrophobic reaction with an increase in the cell surface hydrophobicity after irradiation. Scanning electron microscopy of irradiated C. tropicalis showed marked abnormalities in cell shape and size with significant reduction in adherence ability at the MIC level of Nystatin (4 μg/ml). More basic research at the level of pathogenesis and catheter substance is needed to design novel strategies to prevent fungal adherence and to inhibit biofilm formation.

  9. Particle Fabrication Using Inkjet Printing onto Hydrophobic Surfaces for Optimization and Calibration of Trace Contraband Detection Sensors

    Directory of Open Access Journals (Sweden)

    Greg Gillen

    2015-11-01

    Full Text Available A method has been developed to fabricate patterned arrays of micrometer-sized monodisperse solid particles of ammonium nitrate on hydrophobic silicon surfaces using inkjet printing. The method relies on dispensing one or more microdrops of a concentrated aqueous ammonium nitrate solution from a drop-on-demand (DOD inkjet printer at specific locations on a silicon substrate rendered hydrophobic by a perfluorodecytrichlorosilane monolayer coating. The deposited liquid droplets form into the shape of a spherical shaped cap; during the evaporation process, a deposited liquid droplet maintains this geometry until it forms a solid micrometer sized particle. Arrays of solid particles are obtained by sequential translation of the printer stage. The use of DOD inkjet printing for fabrication of discrete particle arrays allows for precise control of particle characteristics (mass, diameter and height, as well as the particle number and spatial distribution on the substrate. The final mass of an individual particle is precisely determined by using gravimetric measurement of the average mass of solution ejected per microdrop. The primary application of this method is fabrication of test materials for the evaluation of spatially-resolved optical and mass spectrometry based sensors used for detecting particle residues of contraband materials, such as explosives or narcotics.

  10. Thermodynamics and kinetics of reduction and species conversion at a hydrophobic surface for mitochondrial cytochromes c and their cardiolipin adducts

    International Nuclear Information System (INIS)

    Ranieri, Antonio; Di Rocco, Giulia; Millo, Diego; Battistuzzi, Gianantonio; Bortolotti, Carlo A.; Lancellotti, Lidia; Borsari, Marco; Sola, Marco

    2015-01-01

    Highlights: • Cytochrome c and its adduct with cardiolipin can be immobilized on a hydrophobic SAM. • Adsorbed cytochrome c and its adduct undergo extensive unfolding and axial ligand substitution. • An equilibrium between a six-coordinated and a five-coordinated form is observed in both cases. • The reduced five-coordinated form is stabilized by cardiolipin binding. • Immobilized cytochrome c exchanges electrons more slowly upon cardiolipin binding. - Abstract: Cytochrome c (cytc) and its adduct with cardiolipin (CL) were immobilized on a hydrophobic SAM-coated electrode surface yielding a construct which mimics the environment experienced by the complex at the inner mitochondrial membrane where it plays a role in cell apoptosis. Under these conditions, both species undergo an equilibrium between a six-coordinated His/His-ligated and a five-coordinated His/- ligated forms stable in the oxidized and in the reduced state, respectively. The thermodynamics of the oxidation-state dependent species conversion were determined by temperature-dependent diffusionless voltammetry experiments. CL binding stabilizes the immobilized reduced His/- ligated form of cytc which was found previously to catalytically reduce dioxygen. Here, this adduct is also found to show pseudoperoxidase activity, catalysing reduction of hydrogen peroxide. These effects would impart CL with an additional role in the cytc-mediated peroxidation leading to programmed cell death. Moreover, immobilized cytc exchanges electrons more slowly upon CL binding possibly due to changes in solvent reorganization effects at the protein-SAM interface

  11. Surface analysis of PEGylated nano-shields on nanoparticles installed by hydrophobic anchors

    DEFF Research Database (Denmark)

    Ebbesen, M F; Whitehead, Bradley Joseph; Gonzalez, Borja Ballarin

    2013-01-01

    Purpose: This work describes a method for functionalisation of nanoparticle surfaces with hydrophilic "nano-shields" and the application of advanced surface characterisation to determine PEG amount and accumulation at the outmost 10 nm surface that is the predominant factor in determining protein....... Surface and bulk analysis was performed including X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR) and zeta potential. Cellular uptake was investigated in RAW 264.7 macrophages by flow cytometry. Results: Sub-micron nanoparticles were formed and the combination of (NMR...

  12. Construction of super-hydrophobic iron with a hierarchical surface structure

    Science.gov (United States)

    Yuan, Zhiqing; Bin, Jiping; Wang, Xian; Wang, Menglei; Peng, Chaoyi; Xing, Suli; Xiao, Jiayu; Zeng, Jingcheng; Xiao, Ximei; Fu, Xin

    2014-04-01

    Wettability of an iron surface is crucial for the wide applications of iron in practice. In this work, a hierarchical structure highly similar to that of the underside of a bamboo leaf was constructed on an iron surface via the template method and controllable etching. After modification by stearic acid, the iron surface with hierarchical structure showed excellent water repellency, with an average contact angle of 156° and a sliding angle of 3°. X-ray diffraction (XRD) techniques and Fourier transform infrared spectroscopy (FTIR) are applied to examine the chemical components of an iron surface.

  13. Construction of hydrophobic wood surfaces by room temperature deposition of rutile (TiO2) nanostructures

    Science.gov (United States)

    Rongbo Zheng; Mandla A. Tshabalala; Qingyu Li; Hongyan Wang

    2015-01-01

    A convenient room temperature approach was developed for growing rutile TiO2 hierarchical structures on the wood surface by direct hydrolysis and crystallization of TiCl3 in saturated NaCl aqueous solution.The morphology and the crystal structure of TiO2 coated on the wood surface were characterized...

  14. Effects of trimethylsilane plasma coating on the hydrophobicity of denture base resin and adhesion of Candida albicans on resin surfaces.

    Science.gov (United States)

    Liu, Tianshuang; Xu, Changqi; Hong, Liang; Garcia-Godoy, Franklin; Hottel, Timothy; Babu, Jegdish; Yu, Qingsong

    2017-12-01

    Candida-associated denture stomatitis is the most common oral mucosal lesion among denture wearers. Trimethylsilane (TMS) plasma coating may inhibit the growth of Candida albicans on denture surfaces. The purpose of this in vitro study was to investigate whether TMS plasma coatings can effectively reduce C albicans adhesion on denture base acrylic resin surfaces. Sixty denture base acrylic resin disks with smooth and rough surfaces were prepared and were either left untreated (control group) or coated with TMS monomer (experimental group) by using plasma. Contact angles were measured immediately after TMS plasma coating. The morphology of C albicans adhesion was observed with scanning electron microscopy (SEM). Energy-dispersive spectroscopy (EDS) was used to characterize the elemental composition of the specimen surface. An adhesion test was performed by incubating the resin disk specimens in C albicans suspensions (1×10 7 cells/mL) at 37°C for 24 hours and further measuring the optical density of the C albicans by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay test. One-way ANOVA and 2-way ANOVA were followed by a post hoc test analysis (α=.05). The group with TMS coating exhibited a more hydrophobic surface than the control group. EDS analysis revealed successful TMS plasma coating. The difference in the mean contact angles between the uncoated group and the TMS-coated group was statistically significant (Pcoating than on the surfaces of the experimental group. In the adhesion test, the amount of C albicans adhering to the surface of denture base resin with the TMS coating was significantly less than that on the surfaces without TMS coating (Pcoating significantly reduced the adhesion of C albicans to the denture base resin and may reduce denture stomatitis. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  15. Adsorption and nanowear properties of bovine submaxillary mucin films on solid surfaces: Influence of solution pH and substrate hydrophobicity

    DEFF Research Database (Denmark)

    Sotres, Javier; Madsen, Jan Busk; Arnebrant, Thomas

    2014-01-01

    The adsorption and mechanical stability of bovine submaxillary mucins (BSM) films at solid-liquid interfaces were studied with respect to both substrate hydrophobicity and solution pH. Dynamic light scattering revealed a single peak distribution in neutral aqueous solution (pH 7.4) and a small...... fraction with enhanced aggregation was observed in acidic solution (pH 3.8). Both substrate hydrophobicity and solution pH were found to affect the spontaneous adsorption of BSM onto solid surfaces; BSM adsorbed more onto hydrophobic surfaces than hydrophilic ones, and adsorbed more at pH 3.8 than at pH 7.......4. Thus, the highest "dry" adsorbed mass was observed for hydrophobic surfaces in pH 3.8 solution. However, a highest "wet" adsorbed mass, i.e. which includes the solvent coupled to the film, was observed for hydrophobic surfaces at pH 7.4. The mechanical stability of the films was studied...

  16. Surface analysis and anti-graffiti behavior of a weathered polyurethane-based coating embedded with hydrophobic nano silica

    Science.gov (United States)

    Rabea, A. Mohammad; Mohseni, M.; Mirabedini, S. M.; Tabatabaei, M. Hashemi

    2012-03-01

    In this study, a permanent anti-graffiti polyurethane coating was prepared using concomitant loading of an OH-functional silicone modified polyacrylate additive ranging from 2 to 15 mol% and hydrophobic silica nanoparticles from 1 to 5 wt%. UV-visible spectroscopy, contact angle measurement and dynamic mechanical thermal analysis (DMTA) analysis were conducted on selected samples to study the weathering performance of samples containing various amounts of silica nanoparticles before and after accelerated weathering conditions. The results showed that higher amounts of additive had inferior effects on the anti-graffiti performance of the coating samples after exposure. However, silica nanoparticles could positively affect the anti-graffiti performance against ageing cycles. This improvement was attributed to lower degradation of samples containing silica nanoparticles and barrier property of nanoparticles against graffiti penetration. The presence of silica nanoparticles did not have any significant effect on the surface free energy of the samples prior and after ageing.

  17. Comparative investigation on a hexane-degrading strain with different cell surface hydrophobicities mediated by starch and chitosan.

    Science.gov (United States)

    Chen, Dong-Zhi; Jiang, Ning-Xin; Ye, Jie-Xu; Cheng, Zhuo-Wei; Zhang, Shi-Han; Chen, Jian-Meng

    2017-05-01

    Bioremediation usually exhibits low removal efficiency toward hexane because of poor water solubility, which limits the mass transfer rate between the substrate and microorganism. This work aimed to enhance the hexane degradation rate by increasing cell surface hydrophobicity (CSH) of the degrader, Pseudomonas mendocina NX-1. The CSH of P. mendocina NX-1 was manipulated by treatment with starch and chitosan solution of varied concentrations, reaching a maximum hydrophobicity of 52%. The biodegradation of hexane conformed to the Haldane inhibition model, and the maximum degradation rate (ν max ) of the cells with 52% CSH was 0.72 mg (mg cell) -1 ·h -1 in comparison with 0.47 mg (mg cell) -1 ·h -1 for cells with 15% CSH. The production of CO 2 by high CSH cells was threefold higher than that by cells at 15% CSH within 30 h, and the cumulative rates of O 2 consumption were 0.16 and 0.05 mL/h, respectively. High CSH was related to low negative charge carried by the cell surface and probably reduced the repulsive electrostatic interactions between hexane and microorganisms. The FT-IR spectra of cell envelopes demonstrated that the methyl chain was inversely proportional to increasing CSH values, but proteins exhibited a positive effect to CSH enhancement. The ratio of extracellular proteins and polysaccharides increased from 0.87 to 3.78 when the cells were treated with starch and chitosan, indicating their possible roles in increased CSH.

  18. Unexpectedly strong energy stabilization inside the hydrophobic core of small protein Rubredoxin mediated by aromatic residues: correlated ab initio quantum chemical calculations

    Czech Academy of Sciences Publication Activity Database

    Vondrášek, Jiří; Bendová, Lada; Klusák, Vojtěch; Hobza, Pavel

    2005-01-01

    Roč. 127, č. 8 (2005), s. 2615-2619 ISSN 0002-7863 R&D Projects: GA AV ČR(CZ) IAA400550510 Institutional research plan: CEZ:AV0Z4055905 Keywords : hydrophobic core * globular proteins * stabilization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.419, year: 2005

  19. Surface hydration drives rapid water imbibition into strongly hydrophilic nanopores.

    Science.gov (United States)

    Fang, Chao; Qiao, Rui

    2017-08-09

    The imbibition of liquids into nanopores plays a critical role in numerous applications, and most prior studies focused on imbibition due to capillary flows. Here we report molecular simulations of the imbibition of water into single mica nanopores filled with pressurized gas. We show that, while capillary flow is suppressed by the high gas pressure, water is imbibed into the nanopore through surface hydration in the form of monolayer liquid films. As the imbibition front moves, the water film behind it gradually densifies. Interestingly, the propagation of the imbibition front follows a simple diffusive scaling law. The effective diffusion coefficient of the imbibition front, however, is more than ten times larger than the diffusion coefficient of the water molecules in the water film adsorbed on the pore walls. We clarify the mechanism for the rapid water imbibition observed here.

  20. Hydrophobic surface functionalization of Philippine natural zeolite for a targeted oil remediation application

    Science.gov (United States)

    Osonio, Airah P.; Olegario-Sanchez, Eleanor M.

    2017-12-01

    The objective of this study is to modify and compare the oil sorption capacity on the surface of natural zeolite (NZ) and functionalized natural zeolite (FNZ) and to compare with activated charcoal samples. The NZ samples were surface modified via esterification process and characterized using XRD, SEM, and IR spectroscopy. The NZ, FNZ and activated charcoal were then tested using ASTM method F726-12 to validate the oil sorption capacity and TGA was used for the oil selectivity of the adsorbents. The results indicate that FNZ has an improved oil/water adsorption capacity than NZ when functionalized with ester and has a comparable capacity with activated charcoal.

  1. The fabrication and hydrophobic property of micro-nano patterned surface on magnesium alloy using combined sparking sculpture and etching route

    International Nuclear Information System (INIS)

    Wu, Yunfeng; Wang, Yaming; Liu, Hao; Liu, Yan; Guo, Lixin; Jia, Dechang; Ouyang, Jiahu; Zhou, Yu

    2016-01-01

    Highlights: • A hydrophobic micro-nano roughness surface on magnesium was fabricated. • Micro-nano structure derives from duplicating ‘over growth’ regions by MAO. • 7–9 μm micro-scale big pores insetting with nano-scale fine pores were fabricated. • Hydrophobicity of micro-nano surface was improved by chemical decoration and stearic treatment. - Abstract: Magnesium alloy with micro-nano structure roughness surface, can serve as the loading reservoirs of medicine capsule and industrial lubricating oil, or mimic ‘lotus leaf’ hydrophobic surface, having the potential applications in medical implants, automobile, aerospace and electronic products, etc. Herein, we propose a novel strategy to design a micro-nano structure roughness surface on magnesium alloy using combined microarc sparking sculpture and etching in CrO 3 aqueous solution. A hydrophobic surface (as an applied example) was further fabricated by chemical decorating on the obtained patterned magnesium alloy surface to enhance the corrosion resistance. The results show that the combined micro-nano structure of 7–9 μm diameter big pores insetting with nano-scale fine pores was duplicated after etched the sparking sculptured ‘over growth’ oxide regions towards the magnesium substrate. The micro-nano structure surface was chemically decorated using AgNO 3 and stearic acid, which enables the contact angle increased from 60° to 146.8°. The increasing contact angle is mainly attributed to the micro-nano structure and the chemical composition. The hydrophobic surface of magnesium alloy improved the corrosion potential from −1.521 V of the bare magnesium to −1.274 V. Generally, the sparking sculpture and then etching route demonstrates a low-cost, high-efficacy method to fabricate a micro-nano structure hydrophobic surface on magnesium alloy. Furthermore, our research on the creating of micro-nano structure roughness surface and the hydrophobic treatment can be easily extended to the

  2. The fabrication and hydrophobic property of micro-nano patterned surface on magnesium alloy using combined sparking sculpture and etching route

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yunfeng [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Wang, Yaming, E-mail: wangyaming@hit.edu.cn [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Liu, Hao [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Liu, Yan [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); Guo, Lixin; Jia, Dechang; Ouyang, Jiahu; Zhou, Yu [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China)

    2016-12-15

    Highlights: • A hydrophobic micro-nano roughness surface on magnesium was fabricated. • Micro-nano structure derives from duplicating ‘over growth’ regions by MAO. • 7–9 μm micro-scale big pores insetting with nano-scale fine pores were fabricated. • Hydrophobicity of micro-nano surface was improved by chemical decoration and stearic treatment. - Abstract: Magnesium alloy with micro-nano structure roughness surface, can serve as the loading reservoirs of medicine capsule and industrial lubricating oil, or mimic ‘lotus leaf’ hydrophobic surface, having the potential applications in medical implants, automobile, aerospace and electronic products, etc. Herein, we propose a novel strategy to design a micro-nano structure roughness surface on magnesium alloy using combined microarc sparking sculpture and etching in CrO{sub 3} aqueous solution. A hydrophobic surface (as an applied example) was further fabricated by chemical decorating on the obtained patterned magnesium alloy surface to enhance the corrosion resistance. The results show that the combined micro-nano structure of 7–9 μm diameter big pores insetting with nano-scale fine pores was duplicated after etched the sparking sculptured ‘over growth’ oxide regions towards the magnesium substrate. The micro-nano structure surface was chemically decorated using AgNO{sub 3} and stearic acid, which enables the contact angle increased from 60° to 146.8°. The increasing contact angle is mainly attributed to the micro-nano structure and the chemical composition. The hydrophobic surface of magnesium alloy improved the corrosion potential from −1.521 V of the bare magnesium to −1.274 V. Generally, the sparking sculpture and then etching route demonstrates a low-cost, high-efficacy method to fabricate a micro-nano structure hydrophobic surface on magnesium alloy. Furthermore, our research on the creating of micro-nano structure roughness surface and the hydrophobic treatment can be easily

  3. Fabrication of high aspect ratio nanopillars and micro/nano combined structures with hydrophobic surface characteristics by injection molding

    Science.gov (United States)

    Zhou, Mingyong; Xiong, Xiang; Jiang, Bingyan; Weng, Can

    2018-01-01

    Polymer products with micro/nano-structures have excellent mechanical and optical properties, chemical resistance, and other advantages. Injection molding is one of the most potential techniques to fabricate polymer products with micro/nano-structures artificially in large numbers. In this study, a surface approach to fabricate high aspect ratio nanopillars and micro/nano combined structures was presented. Mold insert with micropillar arrays and nanopillars on its surface was prepared by combing anodic aluminum oxide (AAO) template and etched plate. Anti-sticking modification was done on the template to realize a better demolding quality. The influences of mold temperature and polymer material on the final replication quality were investigated. The results showed that the final replication quality of high aspect ratio nanopillars was greatly improved as compared with the unprocessed template. Polymer with low elongation at break was not suitable to fabricate structures with high aspect ratio via injection molding. For polypropylene surface, the experimental results of static contact angles were almost consistent with Cassie-Baxter equation. When the mold temperature reached 178 °C, hair-like polycarbonate nanopillars were observed, resulting in an excellent hydrophobic characteristic.

  4. Spontaneous Structuration of Hydrophobic Polymer Surfaces in Contact with Salt Solutions

    NARCIS (Netherlands)

    Sîretanu, Igor; Saadaoui, Hassan; Chapel, Jean Paul; Drummond, Carlos; Rodriguez-Hernandez, Juan; Drummond, Carlos

    2015-01-01

    It has been described in previous chapters how spontaneous instabilities related to interfacial phenomena can be used to produce controlled patterns on polymer surfaces. Strategies of polymer patterning assisted by dewetting or water drop condensation were described. In this chapter we present a

  5. Structural changes and molecular interactions of hydrophobin SC3 in solution and on a hydrophobic surface

    NARCIS (Netherlands)

    Wang, X.; Vocht, M.L. de; Poolman, B.; Robillard, G.T.; Wang, [No Value; Jonge, J. de

    2002-01-01

    The hydrophobin SC3 belongs to a class of small proteins functioning in the growth and development of fungi. Its unique amphipathic property and remarkable surface activity make it interesting not only for biological studies but also for medical and industrial applications. Biophysical studies have

  6. Bacterial adhesion and biofilm formation on surfaces of variable roughness and hydrophobicity

    DEFF Research Database (Denmark)

    Tang, Lone; Pillai, Saju; Iversen, Anders

    L.Biofilm formation on surfaces in food production and processing can deteriorate the quality of food products and be a hazard to consumers. The food industry currently uses a number of approaches to either remove biofilm or prevent its formation. Due to the inherent resilience of bacteria...

  7. Biosurfactant-enhanced bioremediation of hydrophobic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Cameotra, S.S.; Makkar, R.S. [Inst. of Microbial Technology, Chandigarh (India)

    2010-01-15

    Biosurfactants are surface-active compounds synthesized by a wide variety of microorganisms. They are molecules that have both hydrophobic and - philic domains and are capable of lowering the surface tension and the interfacial tension of the growth medium. Biosurfactants possess different chemical structures-lipopeptides, glycolipids, neutral lipids, and fatty acids. They are nontoxic biomolecules that are biodegradable. Biosurfactants also exhibit strong emulsification of hydrophobic compounds and form stable emulsions. Polycyclic aromatic hydrocarbons (PAHs), crude on sludge, and pesticides call be toxic, mutagenic, and carcinogenic compounds that pollute the environment. They are released into the environment as a result of oil spillage and by-products of coal treatment processes. The low water solubility of these compounds limits their availability to microorganisms, which is a potential problem for bioremediation of contaminated sites. Microbially produced surfactants enhance the bioavailability of these hydrophobic compounds for bioremediation. Therefore, biosurfactant-enhanced solubility of pollutants has potential hioremediation applications.

  8. Competitive adsorption of monoclonal antibodies and nonionic surfactants at solid hydrophobic surfaces

    DEFF Research Database (Denmark)

    Kapp, Sebastian J; Larsson, Iben; van de Weert, Marco

    2015-01-01

    , such as infusion bags and i.v. lines. Total internal reflection fluorescence and quartz crystal microbalance with dissipation monitoring were used to follow and quantify this. Furthermore, the influence of the nonionic surfactant polysorbate 80 (PS80) on the adsorption process of these two antibodies...... was investigated. Despite belonging to two different IgG subclasses, both antibodies displayed comparable adsorption behavior. Both antibodies readily adsorbed in the absence of PS80, whereas adsorption was reduced in the presence of 30 mg/L surfactant. The sequence of exposure of the surfactant and protein...... to the surface was found to have a major influence on the extent of protein adsorption. Although only a fraction of adsorbed protein could be removed by rinsing with 30 mg/L surfactant solution, adsorption was entirely prevented when surfaces were pre-exposed to PS80. © 2014 Wiley Periodicals, Inc...

  9. Engineering of Nanoscale Antifouling and Hydrophobic Surfaces on Naval Structural Steel HY-80 by Anodizing

    Science.gov (United States)

    2015-06-01

    form a biofilm—an assemblage of attached cells, which is commonly referred to as slime [29]. These microorganisms adhere to the surface by...extracellular polymeric substances (EPS). So the biofilm, which is the result of micro fouling, comprises both the microorganisms and the EPS, and thus the... sponges , anemones, tunicates, and hydroids, whilst hard fouling comprises invertebrates such as barnacles, mussels, and tubeworms. The specific

  10. Particle size, surface hydrophobicity and interaction with serum of parenteral fat emulsions and model drug carriers as parameters related to RES uptake.

    Science.gov (United States)

    Carrstensen, H; Müller, R H; Müller, B W

    1992-10-01

    Fat emulsions for parenteral nutrition, stabilized by egg lecithin, were characterized in terms of parameters relevant to uptake by the reticuloendothelial system (RES), e.g. size distribution, surface hydrophobicity and adsorption of serum components as a measure of the degree of opsonization. Adsorption of serum components was quantified by zeta potential measurement. Fat emulsions for nutrition were compared with emulsions used for drug delivery and model drug carries for intravenous injection. The emulsions for drug delivery were stabilized by the blockcopolymers Poloxamer 188 and 407 (Pluronic F68 and F127) and Poloxamine 908. Model drug carriers were hydrophobic and hydrophilic polystyrene latex particles. Hydrophilic particles were prepared by adsorption of Poloxamine 908 (coating) onto the particle surface. The hydrophobicity and serum protein adsorption decreased from hydrophobic latex particles to egg lecithin emulsions and blockcopolymer emulsions and particles. The data correlated with that in the literature concerning liver uptake in vivo showing complete RES clearance of hydrophobic latex particles, reduced uptake of egg lecithin emulsions and avoidance of RES uptake by Poloxamine 908 coated particles.

  11. Confined laminar flow on a super-hydrophobic surface drives the initial stages of tau protein aggregation

    KAUST Repository

    Moretti, Manola

    2018-02-01

    Super-hydrophobic micro-patterned surfaces are ideal substrates for the controlled self-assembly and substrate-free characterization of biological molecules. In this device, the tailored surface supports a micro-volume drop containing the molecules of interest. While the quasi-spherical drop is evaporating under controlled conditions, its de-wetting direction is guided by the pillared microstructure on top of the device, leading to the formation of threads between the neighboring pillars. This effect has been exploited here to elucidate the mechanism triggering the formation of amyloid fibers and oligomers in tau related neurodegenerative diseases. By using Raman spectroscopy, we demonstrate that the fiber bridging the pillars contains β-sheets, a characteristic feature of amyloid aggregation. We propose that the combination of laminar flow, shear stress and molecular crowding taking place while the drop is evaporating on the SHMS, induces the reorganization of the tau protein secondary structure and we suggest that this effect could in fact closely mimic the actual mechanism occurring in the human brain environment. Such a straightforward technique opens up new possibilities in the field of self-assembly of biomolecules and their characterization by different methods (SEM, AFM, Raman spectroscopy, TEM), in a single device.

  12. No relationship between the cell surface hydrophobicity of coagulase-negative staphylococci and their ability to adhere onto fluorinated poly(ethylene-propylene)

    NARCIS (Netherlands)

    Brokke, P.; Brokke, P.; Dankert, J.; Hogt, A.H.; Feijen, Jan

    1992-01-01

    The cell surface hydrophobicity of 14 encapsulated and 21 non-encapsulated coagulase-negative staphylococci (CN staph) as determined with the salt aggregation test (SAT) as well as with the xylene-water method ranged widely. Non-encapsulated strains adhered well onto fluorinated

  13. Detachment of colloidal particles from collector surfaces with different electrostatic charge and hydrophobicity by attachment to air bubbles in a parallel plate flow chamber

    NARCIS (Netherlands)

    Suarez, CG; van der Mei, HC; Busscher, HJ

    1999-01-01

    The detachment of polystyrene particles adhering to collector surfaces with different electrostatic charge and hydrophobicity by attachment to a passing air bubble has been studied in a parallel plate flow chamber. Particle detachment decreased linearly with increasing air bubble velocity and

  14. New insight in the structural features of haloadaptation in α-amylases from halophilic Archaea following homology modeling strategy: folded and stable conformation maintained through low hydrophobicity and highly negative charged surface

    Science.gov (United States)

    Zorgani, Mohamed Amine; Patron, Kevin; Desvaux, Mickaël

    2014-07-01

    Proteins from halophilic archaea, which live in extreme saline conditions, have evolved to remain folded, active and stable at very high ionic strengths. Understanding the mechanism of haloadaptation is the first step toward engineering of halostable biomolecules. Amylases are one of the main enzymes used in industry. Yet, no three-dimensional structure has been experimentally resolved for α-amylases from halophilic archaea. In this study, homology structure modeling of α-amylases from the halophilic archaea Haloarcula marismortui, Haloarcula hispanica, and Halalkalicoccus jeotgali were performed. The resulting models were subjected to energy minimization, evaluation, and structural analysis. Calculations of the amino acid composition, salt bridges and hydrophobic interactions were also performed and compared to a set of non-halophilic counterparts. It clearly appeared that haloarchaeal α-amylases exhibited lower propensities for helix formation and higher propensities for coil-forming regions. Furthermore, they could maintain a folded and stable conformation in high salt concentration through highly negative charged surface with over representation of acidic residues, especially Asp, and low hydrophobicity with increase of salt bridges and decrease in hydrophobic interactions on the protein surface. This study sheds some light on the stability of α-amylases from halophilic archaea and provides strong basis not only to understand haloadaptation mechanisms of proteins in microorganisms from hypersalines environments but also for biotechnological applications.

  15. Comparative Analysis of Structural Responses of Rat Subcutaneous Fat on the Implantation of Samples of Polymethyl Methacrylate with Hydrophobic and Hydrophilic Surface.

    Science.gov (United States)

    Kudasova, E O; Vlasova, L F; Semenov, D E; Lushnikova, E L

    2017-03-01

    Morphological analysis of the subcutaneous fat was performed in rats after subcutaneous implantation of basic dental plastic materials with different hydrophobic and hydrophilic properties. It was shown that subcutaneous implantation of dental plastics with mostly hydrophobic surface and low biocompatibility induced destructive and inflammatory processes of various intensities, sometimes with allergic component; morphological signs of processes persisted for 6 weeks. Modification of basic plastics using glow-discharge plasma and enhancement of their hydrophilicity and biocompatibility significantly reduced the intensity of destructive and inflammatory processes and ensured more rapid (in 2 weeks) repair of the destroyed tissues with the formation of fibrous capsule around the implant.

  16. Thermal, Electrical and Surface Hydrophobic Properties of Electrospun Polyacrylonitrile Nanofibers for Structural Health Monitoring.

    Science.gov (United States)

    Alarifi, Ibrahim M; Alharbi, Abdulaziz; Khan, Waseem S; Swindle, Andrew; Asmatulu, Ramazan

    2015-10-14

    This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals with the fabrication of PAN-based nanofibers via electrospinning followed by stabilization and carbonization in order to remove all non-carbonaceous material and ensure pure carbon fibers as the resulting material. Electrochemical impedance spectroscopy was used to determine the ionic conductivity of PAN fibers. The X-ray diffraction study showed that the repeated peaks near 42° on the activated nanofiber film were α and β phases, respectively, with crystalline forms. Contact angle, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were also employed to examine the surface, thermal and chemical properties of the carbonized electrospun PAN fibers. The test results indicated that the carbonized PAN nanofibers have superior physical properties, which may be useful for structural health monitoring (SHM) applications in different industries.

  17. From petal effect to lotus effect: a facile solution immersion process for the fabrication of super-hydrophobic surfaces with controlled adhesion

    Science.gov (United States)

    Cheng, Zhongjun; Du, Ming; Lai, Hua; Zhang, Naiqing; Sun, Kening

    2013-03-01

    In this paper, a convenient approach based on the reaction between an alkyl thiol and hierarchical structured Cu(OH)2 substrates is reported for the fabrication of super-hydrophobic surfaces with controlled adhesion. This reaction can etch the Cu(OH)2 microstructures and simultaneously introduce a coating with low surface energy. By simply controlling the reaction time or the chain length of the thiol, super-hydrophobic surfaces with controlled adhesion can be achieved, and the adhesive force between the surface and the water droplet can be adjusted from extreme low (~14 μN) to very high (~65 μN). The tunable effect of the adhesion is ascribed to the different wetting states for the droplet on the surface that results from the change of the morphology and microstructure scale after the thiolate reaction. Noticeably, the as-prepared surfaces are acid/alkali-resisting; the acidic and basic water droplets have similar contact angles and adhesive forces to that of the neutral water droplet. Moreover, we demonstrate a proof of water droplet transportation for application in droplet-based microreactors via our surfaces. We believe that the results reported here would be helpful for the further understanding of the effect of wetting states on the surface adhesion and the fabrication principle for a super-hydrophobic surface with controlled adhesion.In this paper, a convenient approach based on the reaction between an alkyl thiol and hierarchical structured Cu(OH)2 substrates is reported for the fabrication of super-hydrophobic surfaces with controlled adhesion. This reaction can etch the Cu(OH)2 microstructures and simultaneously introduce a coating with low surface energy. By simply controlling the reaction time or the chain length of the thiol, super-hydrophobic surfaces with controlled adhesion can be achieved, and the adhesive force between the surface and the water droplet can be adjusted from extreme low (~14 μN) to very high (~65 μN). The tunable effect of the

  18. Constructing Fluorine-Free and Cost-Effective Superhydrophobic Surface with Normal-Alcohol-Modified Hydrophobic SiO2 Nanoparticles.

    Science.gov (United States)

    Ye, Hui; Zhu, Liqun; Li, Weiping; Liu, Huicong; Chen, Haining

    2017-01-11

    Superhydrophobic coatings have drawn much attention in recent years for their wide potential applications. However, a simple, cost-effective, and environmentally friendly approach is still lacked. Herein, a promising approach using nonhazardous chemicals was proposed, in which multiple hydrophobic functionalized silica nanoparticles (SiO 2 NPs) were first prepared as core component, through the efficient reaction between amino group containing SiO 2 NPs and the isocyanate containing hydrophobic surface modifiers synthesized by normal alcohols, followed by simply spraying onto various substrates for superhydrophobic functionalization. Furthermore, to further improve the mechanical durability, an organic-inorganic composite superhydrophobic coating was fabricated by incorporating cross-linking agent (polyisocyanate) into the mixture of hydrophobic-functionalized SiO 2 NPs and hydroxyl acrylic resin. The hybrid coating with cross-linked network structures is very stable with excellent mechanical durability, self-cleaning property and corrosion resistance.

  19. The effects of processing conditions on the surface morphology and hydrophobicity of polyvinylidene fluoride membranes prepared via vapor-induced phase separation

    Science.gov (United States)

    Peng, Yuelian; Fan, Hongwei; Ge, Ju; Wang, Shaobin; Chen, Ping; Jiang, Qi

    2012-12-01

    The present investigation reveals how the surface morphology and the hydrophobicity of polyvinylidene fluoride (PVDF) membranes, which were prepared via a vapor-induced phase separation method, were affected by the initial PVDF content in the casting solution and the air temperature. The surface morphology was characterized with scanning electron microscopy. A ternary phase diagram of PVDF/N, N-dimethylacetamide/water was constructed to explain the formation mechanism of the different morphologies. The results show that different membrane morphologies and hydrophobicities can be obtained by changing the processing conditions. Low air temperature and high PVDF contents facilitate the crystallization process, resulting in the formation of a porous skin and particle morphology, which increases the hydrophobicity of the surface. High air temperature and low PVDF contents are favorable for the formation of a net-like surface morphology via spinodal decomposition and lead to a superhydrophobic surface. Theoretical calculations were performed to testify that the net-like surface was more favorable for superhydrophobicity than the particle-based surface.

  20. Permeable reactive barrier of surface hydrophobic granular activated carbon coupled with elemental iron for the removal of 2,4-dichlorophenol in water

    International Nuclear Information System (INIS)

    Yang Ji; Cao Limei; Guo Rui; Jia Jinping

    2010-01-01

    Granular activated carbon was modified with dimethyl dichlorosilane to improve its surface hydrophobicity, and therefore to improve the performance of permeable reactive barrier constructed with the modified granular activated carbon and elemental iron. X-ray photoelectron spectroscopy shows that the surface silicon concentration of the modified granular activated carbon is higher than that of the original one, leading to the increased surface hydrophobicity. Although the specific surface area decreased from 895 to 835 m 2 g -1 , the modified granular activated carbon could adsorb 20% more 2,4-dichlorophenol than the original one did in water. It is also proven that the permeable reactive barrier with the modified granular activated carbon is more efficient at 2,4-dichlorophenol dechlorination, in which process 2,4-dichlorophenol is transformed to 2-chlorophenol or 4-chlorophenol then to phenol, or to phenol directly.

  1. Permeable reactive barrier of surface hydrophobic granular activated carbon coupled with elemental iron for the removal of 2,4-dichlorophenol in water

    Energy Technology Data Exchange (ETDEWEB)

    Yang Ji, E-mail: yangji@ecust.edu.cn [School of Resources and Environmental Engineering, State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Cao Limei; Guo Rui; Jia Jinping [School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2010-12-15

    Granular activated carbon was modified with dimethyl dichlorosilane to improve its surface hydrophobicity, and therefore to improve the performance of permeable reactive barrier constructed with the modified granular activated carbon and elemental iron. X-ray photoelectron spectroscopy shows that the surface silicon concentration of the modified granular activated carbon is higher than that of the original one, leading to the increased surface hydrophobicity. Although the specific surface area decreased from 895 to 835 m{sup 2} g{sup -1}, the modified granular activated carbon could adsorb 20% more 2,4-dichlorophenol than the original one did in water. It is also proven that the permeable reactive barrier with the modified granular activated carbon is more efficient at 2,4-dichlorophenol dechlorination, in which process 2,4-dichlorophenol is transformed to 2-chlorophenol or 4-chlorophenol then to phenol, or to phenol directly.

  2. Mesoscopic Simulations of the Phase Behavior of Aqueous EO 19 PO 29 EO 19 Solutions Confined and Sheared by Hydrophobic and Hydrophilic Surfaces

    KAUST Repository

    Liu, Hongyi

    2012-01-25

    The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs -1 and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO mPO nEO m) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones. © 2011 American Chemical Society.

  3. A facile method of hydrophobic surface modification for acrylonitrile-styrene-acrylate terpolymer based on the out-migration property of metallic soaps

    Science.gov (United States)

    Qi, Yanli; Chen, Tingting; Zhang, Jun

    2018-03-01

    Hydrophobic surface modification is conducted in this study by using additives with long alkyl chains. Several kinds of metallic soaps, such as calcium stearate (CaSt), zinc stearate (ZnSt), magnesium stearate (MgSt) and barium stearate (BaSt) were employed. Polymer matrix is acrylonitrile-styrene-acrylate (ASA) terpolymer due to its wonderful weather resistance property. The surface chemical characterization was studied by Fourier transformed infrared (FTIR) technology and X-ray photoelectron spectroscopy (XPS). Carboxylate (Osbnd Csbnd O-) indexes of composites in both transmittance and reflection modes were calculated according to FTIR results. As to the ratio of carboxylate index in reflection mode to that in transmittance mode, the sample added with 5 wt% ZnSt shows a higher value of 8.77, and a much higher value of 14.47 for the sample added with 10 wt% ZnSt. The corresponding Csbnd C/ Csbnd H /Cdbnd C peak areas of the samples added with 5 wt% or 10 wt% ZnSt are 75.4% and 77.3% respectively, much higher than other samples. This indicates ZnSt is much easier to out-migrate to material surface and therefore is more suitable for hydrophobic surface modification. In particular, the water contact angle of the ASA/ZnSt composite added with 10 wt% ZnSt significantly increased to 127o (40o increase in comparison with pure ASA), successfully converting the surface wettability from hydrophilic to hydrophobic.

  4. Effect of surface hydrophobicity on the dynamics of water at the nanoscale confinement: A molecular dynamics simulation study

    International Nuclear Information System (INIS)

    Choudhury, Niharendu

    2013-01-01

    Highlights: • We present atomistic MD simulation of water confined between two paraffin-like plates. • Effect of plate hydrophobicity on the confined water dynamics is investigated. • Diffusivity of confined water is calculated from mean squared displacements. • Rotational dynamics of the confined water has bimodal nature of relaxation. • Monotonic dependence of translational and rotational dynamics on hydrophobicity. - Abstract: We present detailed molecular dynamics simulations of water in and around a pair of plates immersed in water to investigate the effect of degree of hydrophobicity or hydrophilicity of the plates on dynamics of water confined between the two plates. The nature of the plate has been tuned from hydrophobic to hydrophilic and vice versa by varying plate-water dispersion interaction. Analyses of the translational dynamics as performed by calculating mean squared displacements of the confined water reveal a monotonically decreasing trend of the diffusivity with increasing hydrophilicity of the plates. Orientational dynamics of the confined water also follows the same monotonic trend. Although orientational time constant almost does not change with the increase of plate-water dispersion interaction in the hydrophobic regime corresponding to the smaller plate-water attraction, it changes considerably in the hydrophilic regime corresponding to larger plate-water dispersion interactions

  5. Effects of content and surface hydrophobic modification of BaTiO3 on the cooling properties of ASA (acrylonitrile-styrene-acrylate copolymer)

    Science.gov (United States)

    Xiang, Bo; Zhang, Jun

    2018-01-01

    For the field of cool material, barium titanate (BaTiO3, BT) is still a new member that needs to be further studied. Herein, the effects of both content and surface hydrophobic modification of BT on the cooling properties of acrylonitrile-styrene-acrylate copolymer (ASA) were detailedly investigated, aiming to fabricate composited cool material. Butyl acrylate (BA) was employed to convert the surface of BT from hydrophilic to hydrophobic. The addition of unmodified BT could significantly improve the solar reflectance of ASA, especially when the addition amount is 3 vol%, the near infrared (NIR) reflectance increased from 22.02 to 72.60%. However, serious agglomeration occurred when the addition amount increased to 5 vol% and therefore led to a relatively smaller increase in solar reflectance and an obvious decline in impact strength. After surface hydrophobic modification, the modified BT (M-BT) presented better dispersibility in ASA matrix, which contributed to the improvement of both solar reflectance and impact strength. In addition, the temperature test provided a more sufficient and intuitive way to evaluate the cooling effect of the composited cool materials, and a significant decrease (over 10 °C) could be achieved in the temperature test when M-BT particles were introduced.

  6. Surface Tension Estimates for Droplet Formation in Slurries with Low Concentrations of Hydrophobic Particles, Polymer Flocculants or Surface-Active Contaminants

    Energy Technology Data Exchange (ETDEWEB)

    Gauglitz, Phillip A.; Mahoney, Lenna A.; Blanchard, Jeremy; Bamberger, Judith A.

    2011-06-10

    In support of the K-Basin project, Pacific Northwest National Laboratory (PNNL) was requested to evaluate the appropriate surface tension value to use in models predicting the formation of droplets from spray leaks of K-Basin slurries. The specific issue was whether it was more appropriate to use the surface tension of pure water in model predictions for all plausible spray leaks or to use a lower value. The surface tension of K-Basin slurries is potentially affected not only by particles but by low concentrations of nonionic polyacrylamide flocculant and perhaps by contaminants with surfactant properties, which could decrease the surface tension below that of water. A lower surface tension value typically results in smaller droplets being formed with a larger fraction of droplets in the respirable size range, so using the higher surface tension value of pure water is not conservative and thus needs a strong technical basis.

  7. Strong coupling electrostatics for randomly charged surfaces: antifragility and effective interactions.

    Science.gov (United States)

    Ghodrat, Malihe; Naji, Ali; Komaie-Moghaddam, Haniyeh; Podgornik, Rudolf

    2015-05-07

    We study the effective interaction mediated by strongly coupled Coulomb fluids between dielectric surfaces carrying quenched, random monopolar charges with equal mean and variance, both when the Coulomb fluid consists only of mobile multivalent counterions and when it consists of an asymmetric ionic mixture containing multivalent and monovalent (salt) ions in equilibrium with an aqueous bulk reservoir. We analyze the consequences that follow from the interplay between surface charge disorder, dielectric and salt image effects, and the strong electrostatic coupling that results from multivalent counterions on the distribution of these ions and the effective interaction pressure they mediate between the surfaces. In a dielectrically homogeneous system, we show that the multivalent counterions are attracted towards the surfaces with a singular, disorder-induced potential that diverges logarithmically on approach to the surfaces, creating a singular but integrable counterion density profile that exhibits an algebraic divergence at the surfaces with an exponent that depends on the surface charge (disorder) variance. This effect drives the system towards a state of lower thermal 'disorder', one that can be described by a renormalized temperature, exhibiting thus a remarkable antifragility. In the presence of an interfacial dielectric discontinuity, the singular behavior of counterion density at the surfaces is removed but multivalent counterions are still accumulated much more strongly close to randomly charged surfaces as compared with uniformly charged ones. The interaction pressure acting on the surfaces displays in general a highly non-monotonic behavior as a function of the inter-surface separation with a prominent regime of attraction at small to intermediate separations. This attraction is caused directly by the combined effects from charge disorder and strong coupling electrostatics of multivalent counterions, which dominate the surface-surface repulsion due to

  8. Significance of the rdar and bdar morphotypes in the hydrophobicity and attachment to abiotic surfaces of Salmonella Sofia and other poultry-associated Salmonella serovars.

    Science.gov (United States)

    Chia, T W R; McMeekin, T A; Fegan, N; Dykes, G A

    2011-11-01

    To investigate the relative role of the red dry and rough (rdar) and brown dry and rough (bdar) morphotypes on hydrophobicity and ability to attach to abiotic surfaces of poultry-associated Salmonella strains with a focus on S. Sofia. Cellulose synthase gene null mutants were constructed in five Salmonella strains converting them from rdar to bdar morphotypes. One S. Sofia null mutant displayed reduced hydrophobicity and attachment to Teflon® relative to its parent strain. The S. Virchow and S. Infantis null mutants attached less well to glass relative to their parent strains. The rdar or bdar morphotype may influence S. Sofia persistence but did not explain why bdar strains predominate in this serotype. This work provides some insight into why some Salmonella strains survive in poultry environments and may ultimately contribute to their control. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

  9. Mutations in the hydrophobic surface of an amphipathic groove of 14-3-3zeta disrupt its interaction with Raf-1 kinase.

    Science.gov (United States)

    Wang, H; Zhang, L; Liddington, R; Fu, H

    1998-06-26

    14-3-3 proteins bind to a diverse group of regulatory molecules such as Raf-1, Cbl, and c-Bcr that are involved in signal transduction pathways. The crystal structure of 14-3-3zeta reveals a conserved amphipathic groove that may mediate the association of 14-3-3 with diverse ligands. Consistently, mutations on the charged surface of the groove (Lys-49, Arg-56, and Arg-60) decrease the binding of 14-3-3zeta to the ligands tested (Zhang, L., Wang, H., Liu, D., Liddington, R., and Fu, H. (1997) J. Biol. Chem. 272, 13717-13724). Here we report that mutations that altered the hydrophobic property of the groove, V176D, L216D, L220D, and L227D, disrupted the interaction of 14-3-3zeta with Raf-1 kinase. The reduced binding of the 14-3-3zeta mutants to Raf-1 was apparently not because of gross structural changes in the mutants as judged by their ability to form dimers, by partial proteolysis profiles, and by circular dichroism analysis. These hydrophobic residues appeared to be required for the binding of 14-3-3zeta to distinct activation states of Raf-1 because mutations V176D, L216D, L220D, and L227D reduced the interaction of 14-3-3zeta with Raf-1 from both phorbol 12-myristate 13-acetate-stimulated and unstimulated Jurkat T cells. These same mutations also disrupted the association of 14-3-3zeta with other regulatory molecules such as Cbl and c-Bcr, suggesting that the hydrophobic surface of the amphipathic groove represents part of a binding site shared by a number of 14-3-3-associated proteins. The conservation of the hydrophobic residues Val-176, Leu-216, Leu-220, and Leu-227 among known 14-3-3 family members implies their general importance in ligand binding.

  10. Effect of Eugenol on Cell Surface Hydrophobicity, Adhesion, and Biofilm of Candida tropicalis and Candida dubliniensis Isolated from Oral Cavity of HIV-Infected Patients

    Directory of Open Access Journals (Sweden)

    Suelen Balero de Paula

    2014-01-01

    Full Text Available Most Candida spp. infections are associated with biofilm formation on host surfaces. Cells within these communities display a phenotype resistant to antimicrobials and host defenses, so biofilm-associated infections are difficult to treat, representing a source of reinfections. The present study evaluated the effect of eugenol on the adherence properties and biofilm formation capacity of Candida dubliniensis and Candida tropicalis isolated from the oral cavity of HIV-infected patients. All isolates were able to form biofilms on different substrate surfaces. Eugenol showed inhibitory activity against planktonic and sessile cells of Candida spp. No metabolic activity in biofilm was detected after 24 h of treatment. Scanning electron microscopy demonstrated that eugenol drastically reduced the number of sessile cells on denture material surfaces. Most Candida species showed hydrophobic behavior and a significant difference in cell surface hydrophobicity was observed after exposure of planktonic cells to eugenol for 1 h. Eugenol also caused a significant reduction in adhesion of most Candida spp. to HEp-2 cells and to polystyrene. These findings corroborate the effectiveness of eugenol against Candida species other than C. albicans, reinforcing its potential as an antifungal applied to limit both the growth of planktonic cells and biofilm formation on different surfaces.

  11. Generic strong coupling behavior of Cooper pairs in the surface of superfluid nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Pillet, N. [DPTA/Service de Physique nucleaire, CEA/DAM Ile de France, BP12, F-91680 Bruyeres-le-Chatel (France); Sandulescu, N. [DPTA/Service de Physique nucleaire, CEA/DAM Ile de France, BP12, F-91680 Bruyeres-le-Chatel (France)]|[Institute of Physics and Nuclear Engineering, 76900 Bucharest (Romania)]|[Institut de Physique Nucleaire, CNRS, UMR 8608, Orsay, F-91406 (France); Schuck, P. [Institut de Physique Nucleaire, CNRS, UMR 8608, Orsay, F-91406 (France)]|[Universite Paris-Sud, Orsay, F-91505 (France)

    2007-01-15

    With realistic HFB calculations, using the D1S Gogny force, we reveal a generic behavior of concentration of small sized Cooper pairs (2-3 fm) in the surface of superfluid nuclei. This study confirms and extends previous results given in the literature that use more schematic approaches. It is shown that the strong concentration of pair probability of small Cooper pairs in the nuclear surface is a quite general and generic feature and that nuclear pairing is much closer to the strong coupling regime than previously assumed.

  12. On the Concept of Electrode to Discharge Phenomena in Surface Roughness With Reference Strongly Electronegative Gases

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1986-01-01

    The use of geometrically well-defined protrusions in studies es of the effects of electrode surface roughness upon the insulation strength of strongly electronegative gases is discussed. It is argued that, with respect to the roughness associated with production processes, the dimensions of artif......The use of geometrically well-defined protrusions in studies es of the effects of electrode surface roughness upon the insulation strength of strongly electronegative gases is discussed. It is argued that, with respect to the roughness associated with production processes, the dimensions...

  13. Experimental Investigation on the Effect of Size and Pitch of Hydrophobic Square Patterns on the Pool Boiling Heat Transfer Performance of Cylindrical Copper Surface

    Directory of Open Access Journals (Sweden)

    Sujith Kumar C. S.

    2018-03-01

    Full Text Available In this work, pool boiling heat transfer tests were conducted for investigating the effects of the size and pitch of the hydrophobic square patterns on a copper test piece with the following dimensions: 40 mm long, 25 mm outer diameter, and 18 mm inner diameter. The size of the square patterns and the pitch were varied with an increment of 0.5 mm from 1 mm to 3 mm and from 4.5 to 5.5 mm, respectively. Among the various square patterns of different size and pitch, the 2 mm size square pattern with 5 mm pitch (inter-distance 3 mm was found to be the best because it gives the advantage of bubble coalescence behavior and also the rewetting phenomenon. The observed bubble departure diameter was 2.35 mm, and using this diameter, we predicted the maximum inter-distance between the patterns for producing inter coalescence of bubbles in the axial direction was 3.12 mm. Therefore, a side-by-side distance of 3 mm, which was closed to the estimated inter-distance graphically, can avoid the earlier inter coalescence of the bubbles between patterns on the surface in the axial direction. This results in better pool boiling heat transfer performance. Highlights: (1 Heterogeneous wettable structures were obtained on the copper surface using screen printing techniques; (2 The effect of the size and pitch of the hydrophobic patterns on the bubble dynamics was determined; (3 The wall superheats of all the heterogeneous wettable surfaces were less than the plain copper surface; (4 The highest heat transfer coefficient was obtained from the hydrophobic pattern with 2 mm size and 5 mm pitch.

  14. Microstructural characterization of hydrophobic Ti{sub 1-x}Al{sub x}N coatings with moth-eye-like surface morphology

    Energy Technology Data Exchange (ETDEWEB)

    Godinho, V., E-mail: godinho@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla CSIC-Uni. Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain); Lopez-Santos, C. [NAmur Research Institute for LIfe Sciences (NARILIS), Research Center in Physics of Matter and Radiation (PMR), University of Namur -FUNDP, 61 Rue de Bruxelles, 5000 Namur (Belgium); Rojas, T.C.; Philippon, D.; Jimenez de Haro, M.C. [Instituto de Ciencia de Materiales de Sevilla CSIC-Uni. Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain); Lucas, S. [NAmur Research Institute for LIfe Sciences (NARILIS), Research Center in Physics of Matter and Radiation (PMR), University of Namur - FUNDP, 61 Rue de Bruxelles, 5000 Namur (Belgium); Fernandez, A. [Instituto de Ciencia de Materiales de Sevilla CSIC-Uni. Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Moth-eye-like structures were obtained by changing the power supplied to the targets at a constant N{sub 2} pressure. Black-Right-Pointing-Pointer The antireflecting properties and hydrophobicity of the coatings are discussed. Black-Right-Pointing-Pointer HREM and related techniques revealed the formation of meso- and nano-columns and different degree of open porosity. - Abstract: Ti{sub 1-x}Al{sub x}N thin films with different Al content were deposited by magnetron sputtering. The combination of electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) was used to evaluate the composition of the coatings. The effect of Al content on the morphology and properties of the coatings was investigated. High resolution electron microscopy and related techniques revealed the formation of a pillared moth-eye-like nanostructure with variable size and distribution of meso- and nano-columns and different degree of open porosity that depends on the Al content on the coating. For low Al content (x {<=} 0.21) c-(Ti,Al)N highly porous columns ending in a sharp pyramidal shape present low reflectivity and high hydrophobicity. While the precipitation of h-AlN phase at the column boundaries for x = 0.71 suppresses the c-(Ti,Al)N columnar growth and produces a smother surface, with higher reflectivity and less hydrophobic character.

  15. A hydrophobic gold surface triggers misfolding and aggregation of the amyloidogenic Josephin domain in monomeric form, while leaving the oligomers unaffected.

    Directory of Open Access Journals (Sweden)

    Alessandra Apicella

    Full Text Available Protein misfolding and aggregation in intracellular and extracellular spaces is regarded as a main marker of the presence of degenerative disorders such as amyloidoses. To elucidate the mechanisms of protein misfolding, the interaction of proteins with inorganic surfaces is of particular relevance, since surfaces displaying different wettability properties may represent model systems of the cell membrane. Here, we unveil the role of surface hydrophobicity/hydrophilicity in the misfolding of the Josephin domain (JD, a globular-shaped domain of ataxin-3, the protein responsible for the spinocerebellar ataxia type 3. By means of a combined experimental and theoretical approach based on atomic force microscopy, Fourier transform infrared spectroscopy and molecular dynamics simulations, we reveal changes in JD morphology and secondary structure elicited by the interaction with the hydrophobic gold substrate, but not by the hydrophilic mica. Our results demonstrate that the interaction with the gold surface triggers misfolding of the JD when it is in native-like configuration, while no structural modification is observed after the protein has undergone oligomerization. This raises the possibility that biological membranes would be unable to affect amyloid oligomeric structures and toxicity.

  16. Hydrophobic nano-carrier for lysozyme adsorption

    Indian Academy of Sciences (India)

    phobic interaction chromatography' to describe the separation of proteins adsorbed onto hydrophobic medium by salts [19]. HIC is based on the interaction between hydrophobic ligand carrying support material and hydrophobic amino acids bear- ing non-polar regions of protein surface [20]. The main driv- ing force for this ...

  17. Spectral asymptotics of a strong delta ' interaction supported by a surface

    Czech Academy of Sciences Publication Activity Database

    Exner, Pavel; Jex, M.

    2014-01-01

    Roč. 378, 30-31 (2014), s. 2091-2095 ISSN 0375-9601 R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : delta ' surface interaction * strong coupling expansion Subject RIV: BE - Theoretical Physics Impact factor: 1.683, year: 2014

  18. Spectral asymptotics of a strong δ′ interaction supported by a surface

    International Nuclear Information System (INIS)

    Exner, Pavel; Jex, Michal

    2014-01-01

    Highlights: • Attractive δ ′ interactions supported by a smooth surface are considered. • Surfaces can be either infinite and asymptotically planar, or compact and closed. • Spectral asymptotics is determined by the geometry of the interaction support. - Abstract: We derive asymptotic expansion for the spectrum of Hamiltonians with a strong attractive δ ′ interaction supported by a smooth surface in R 3 , either infinite and asymptotically planar, or compact and closed. Its second term is found to be determined by a Schrödinger type operator with an effective potential expressed in terms of the interaction support curvatures

  19. Strong asymmetry for surface modes in nonlinear lattices with long-range coupling

    International Nuclear Information System (INIS)

    Martinez, Alejandro J.; Vicencio, Rodrigo A.; Molina, Mario I.

    2010-01-01

    We analyze the formation of localized surface modes on a nonlinear cubic waveguide array in the presence of exponentially decreasing long-range interactions. We find that the long-range coupling induces a strong asymmetry between the focusing and defocusing cases for the topology of the surface modes and also for the minimum power needed to generate them. In particular, for the defocusing case, there is an upper power threshold for exciting staggered modes, which depends strongly on the long-range coupling strength. The power threshold for dynamical excitation of surface modes increases (decreases) with the strength of long-range coupling for the focusing (defocusing) cases. These effects seem to be generic for discrete lattices with long-range interactions.

  20. <strong>Cell-surface expression of Hsp70 on hematopoietic cancer cells after inhibition of HDAC activitystrong>

    DEFF Research Database (Denmark)

    Jensen, Helle

    frequently express Hsp70 on their cell surface, whereas the corresponding normal tissues do not. In addition, several clinically applied reagents, such as alkyl-lysophospholipides, chemotherapeutic agents, and anti-inflammatory reagents, have been found to enhance Hsp70 cell surface expression on cancer...

  1. Modelling the fate of hydrophobic organic contaminants in a boreal forest catchment: A cross disciplinary approach to assessing diffuse pollution to surface waters

    International Nuclear Information System (INIS)

    Bergknut, Magnus; Meijer, Sandra; Halsall, Crispin; Agren, Anneli; Laudon, Hjalmar; Koehler, Stephan; Jones, Kevin C.; Tysklind, Mats; Wiberg, Karin

    2010-01-01

    The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day -1 during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons. - The fate of hydrophobic organic contaminants in a boreal forest catchment is connected to the flux of dissolved organic carbon and seasonal deposition.

  2. Density-waves instability and a skyrmion lattice on the surface of strong topological insulators

    Science.gov (United States)

    Baum, Yuval; Stern, Ady

    2012-11-01

    In this work we analyze the instability conditions for spin-density-wave (SDW) formation on the surface of strong topological insulators. We find that for a certain range of Fermi energies and strength of interactions the SDW state is favored compared to the unmagnetized and the uniform-magnetization states. We also find that the SDWs are of spiral nature and, for a certain range of parameters, a Skyrmion lattice may form on the surface. We show that this phase may have a nontrivial Chern number even in the absence of an external magnetic field.

  3. Wind speed and direction shears with associated vertical motion during strong surface winds

    Science.gov (United States)

    Alexander, M. B.; Camp, D. W.

    1984-01-01

    Strong surface winds recorded at the NASA 150-Meter Ground Winds Tower facility at Kennedy Space Center, Florida, are analyzed to present occurrences representative of wind shear and vertical motion known to be hazardous to the ascent and descent of conventional aircraft and the Space Shuttle. Graphical (percentage frequency distributions) and mathematical (maximum, mean, standard deviation) descriptions of wind speed and direction shears and associated updrafts and downdrafts are included as functions of six vertical layers and one horizontal distance for twenty 5-second intervals of parameters sampled simultaneously at the rate of ten per second during a period of high surface winds.

  4. Strong near-surface seismic anisotropy of Taiwan revealed by coda interferometry

    Science.gov (United States)

    Chen, Li-Wei; Chen, Ying-Nien; Gung, Yuancheng; Lee, Jian-Cheng; Liang, Wen-Tzong

    2017-10-01

    We report the near-surface (OPA (Orogeny-Parallel Anisotropy) and SAA (Stress-Aligned Anisotropy). Both types of anisotropy fit well the local geological fabrics and/or the ambient stress, and show strong correlation with the Poisson's ratios at the borehole sites. With these new findings and reported tomographic results, we infer that the SAA are likely confined to the uppermost portion of the crust, in particular to the fluid-saturated late-Quaternary deposits. The strong near-surface anisotropy also implies that delay times contributed by the shallow crust might have been underestimated in studies of shear-wave splitting measurements using the direct arrivals of earthquake waves.

  5. Structural and Mechanical Properties of Thin Films of Bovine Submaxillary Mucin versus Porcine Gastric Mucin on a Hydrophobic Surface in Aqueous Solutions

    DEFF Research Database (Denmark)

    Madsen, Jan Busk; Sotres, Javier; Pakkanen, Kirsi I.

    2016-01-01

    The structural and mechanical properties of thin films generated from two types of mucins, namely, bovine submaxillary mucin (BSM) and porcine gastric mucin (PGM) in aqueous environment were investigated with several bulk and surface analytical techniques. Both mucins generated hydrated films...... on hydrophobic polydimethylsiloxane (PDMS) surfaces from spontaneous adsorption arising from their amphiphilic characteristic. However, BSM formed more elastic films than PGM at neutral pH condition. This structural difference was manifested from the initial film formation processes to the responses to shear...... stresses applied to the films. Acidification of environmental pH led to strengthening the elastic character of BSM films with increased adsorbed mass, whereas an opposite trend was observed for PGM films. We propose that this contrast originates from that negatively charged motifs are present for both...

  6. How Much Surface Coating of Hydrophobic Azithromycin Is Sufficient to Prevent Moisture-Induced Decrease in Aerosolisation of Hygroscopic Amorphous Colistin Powder?

    Science.gov (United States)

    Zhou, Qi Tony; Loh, Zhi Hui; Yu, Jiaqi; Sun, Si-Ping; Gengenbach, Thomas; Denman, John A; Li, Jian; Chan, Hak-Kim

    2016-09-01

    Aerosolisation performance of hygroscopic particles of colistin could be compromised at elevated humidity due to increased capillary forces. Co-spray drying colistin with a hydrophobic drug is known to provide a protective coating on the composite particle surfaces against moisture-induced reduction in aerosolisation performance; however, the effects of component ratio on surface coating quality and powder aerosolisation at elevated relative humidities are unknown. In this study, we have systematically examined the effects of mass ratio of hydrophobic azithromycin on surface coating quality and aerosolisation performance of the co-spray dried composite particles. Four combination formulations with varying drug ratios were prepared by co-spray drying drug solutions. Both of the drugs in each combination formulation had similar in vitro deposition profiles, suggesting that each composite particle comprises two drugs in the designed mass ratio, which is supported by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) data. XPS and ToF-SIMS measurements also revealed that 50% by weight (or 35% by molecular fraction) of azithromycin in the formulation provided a near complete coating of 96.5% (molar fraction) on the composite particle surface, which is sufficient to prevent moisture-induced reduction in fine particle fraction (FPF)recovered and FPFemitted. Higher azithromycin content did not increase coating coverage, while contents of azithromycin lower than 20% w/w did not totally prevent the negative effects of humidity on aerosolisation performance. This study has highlighted that a critical amount of azithromycin is required to sufficiently coat the colistin particles for short-term protection against moisture.

  7. How much surface coating of hydrophobic azithromycin is sufficient to prevent moisture-induced decrease in aerosolisation of hygroscopic colistin powder?

    Science.gov (United States)

    Zhou, Qi (Tony); Loh, Zhi Hui; Yu, Jiaqi; Sun, Si-ping; Gengenbach, Thomas; Denman, John A.; Li, Jian; Chan, Hak-Kim

    2017-01-01

    Aerosolisation performance of hygroscopic particles of colistin could be compromised at elevated humidity due to increased capillary forces. Co-spray drying colistin with a hydrophobic drug is known to provide a protective coating on the composite particle surfaces against moisture-induced reduction in aerosolisation performance; however, the effects of component ratio on surface coating quality and powder aerosolisation at elevated relative humidities are unknown. In this study, we have systematically examined the effects of mass ratio of hydrophobic azithromycin on surface coating quality and aerosolisation performance of the co-spray dried composite particles. Four combination formulations with varying drug ratios were prepared by co-spray drying drug solutions. Both of the drugs in each combination formulation had similar in vitro deposition profiles, suggesting that each composite particle comprise two drugs in the designed mass ratio, which is supported by XPS and ToF-SIMS data. XPS and ToF-SIMS measurements also revealed that 50 % by weight (or 35 % by molecular fraction) of azithromycin in the formulation provided a near-complete coating of 96.5 % (molar fraction) on the composite particle surface, which is sufficient to prevent moisture-induced reduction in FPFrecovered and FPFemitted. Higher azithromycin content did not increase coating coverage, while contents of azithromycin lower than 20 %w/w did not totally prevent the negative effects of humidity on aerosolisation performance. This study has highlighted that a critical amount of azithromycin is required to sufficiently coat the colistin particles for short-term protection against moisture. PMID:27255350

  8. Phosphorylation of hormone-sensitive lipase by protein kinase A in vitro promotes an increase in its hydrophobic surface area

    DEFF Research Database (Denmark)

    Krintel, Christian; Mörgelin, Matthias; Logan, Derek T

    2009-01-01

    Hormone-sensitive lipase (EC 3.1.1.79; HSL) is a key enzyme in the mobilization of fatty acids from stored triacylglycerols. HSL activity is controlled by phosphorylation of at least four serines. In rat HSL, Ser563, Ser659 and Ser660 are phosphorylated by protein kinase A (PKA) in vitro as well...... as in vivo, and Ser660 and Ser659 have been shown to be the activity-controlling sites in vitro. The exact molecular events of PKA-mediated activation of HSL in vitro are yet to be determined, but increases in both Vmax and S0.5 seem to be involved, as recently shown for human HSL. In this study......, the hydrophobic fluorescent probe 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) was found to inhibit the hydrolysis of triolein by purified recombinant rat adipocyte HSL, with a decrease in the effect of bis-ANS upon PKA phosphorylation of HSL. The interaction of HSL with bis-ANS was found to have...

  9. Aqueous electrolyte surfaces in strong electric fields: molecular insight into nanoscale jets and bridges

    Science.gov (United States)

    Jirsák, Jan; Moučka, Filip; Škvor, Jiří; Nezbeda, Ivo

    2015-04-01

    Exposing aqueous surfaces to a strong electric field gives rise to interesting phenomena, such as formation of a floating water bridge or an eruption of a jet in electrospinning. In an effort to account for the phenomena at the molecular level, we performed molecular dynamics simulations using several protocols on both pure water and aqueous solutions of sodium chloride subjected to an electrostatic field. All simulations consistently point to the same mechanisms which govern the rearrangement of the originally planar surface. The results show that the phenomena are primarily governed by an orientational reordering of the water molecules driven by the applied field. It is demonstrated that, for pure water, a sufficiently strong field yields a columnar structure parallel to the field with an anisotropic arrangement of the water molecules with their dipole moments aligned along the applied field not only in the surface layer but over the entire cross section of the column. Nonetheless, the number of hydrogen bonds per molecule does not seem to be affected by the field regardless of its strength and molecule's orientation. In the electrolyte solutions, the ionic charge is able to overcome the effect of the external field tending to arrange the water molecules radially in the first coordination shell of an ion. The ion-water interaction interferes thus with the water-electric field interaction, and the competition between these two forces (i.e., strength of the field versus concentration) provides the key mechanism determining the stability of the observed structures.

  10. Particularities of surface plasmon-exciton strong coupling with large Rabi splitting

    International Nuclear Information System (INIS)

    Symonds, C; Bonnand, C; Plenet, J C; Brehier, A; Parashkov, R; Lauret, J S; Deleporte, E; Bellessa, J

    2008-01-01

    This paper presents some of the particularities of the strong coupling regime occurring between surface plasmon (SP) modes and excitons. Two different active materials were deposited on a silver film: a cyanine dye J-aggregate, and a two-dimensional layered perovskite-type semiconductor. The dispersion relations, which are deduced from angular resolved reflectometry spectra, present an anticrossing characteristic of the strong coupling regime. The wavevector is a good parameter to determine the Rabi splitting. Due to the large interaction energies (several hundreds of milli-electron-volts), the calculations at constant angle can induce an overestimation of the Rabi splitting of more than a factor of two. Another property of polaritons based on SP is their nonradiative character. In order to observe the polaritonic emission, it is thus necessary to use particular extraction setups, such as gratings or prisms. Otherwise only the incoherent emission can be detected, very similar to the bare exciton emission

  11. Energy density and energy flow of surface waves in a strongly magnetized graphene

    Science.gov (United States)

    Moradi, Afshin

    2018-01-01

    General expressions for the energy density and energy flow of plasmonic waves in a two-dimensional massless electron gas (as a simple model of graphene) are obtained by means of the linearized magneto-hydrodynamic model and classical electromagnetic theory when a strong external magnetic field perpendicular to the system is present. Also, analytical expressions for the energy velocity, wave polarization, wave impedance, transverse and longitudinal field strength functions, and attenuation length of surface magneto-plasmon-polariton waves are derived, and numerical results are prepared.

  12. Distribution of Candida albicans and non-albicans Candida species in oral candidiasis patients: Correlation between cell surface hydrophobicity and biofilm forming activities.

    Science.gov (United States)

    Muadcheingka, Thaniya; Tantivitayakul, Pornpen

    2015-06-01

    The purposes of this investigation were to study the prevalence of Candida albicans and non-albicans Candida (NAC) species from oral candidiasis patients and evaluate the cell surface hydrophobicity (CSH) and biofilm forming capacity of the clinical isolates Candida species from oral cavity. This study identified a total of 250 Candida strains isolated from 207 oral candidiasis patients with PCR-RFLP technique. CSH value, total biomass of biofilm and biofilm forming ability of 117 oral Candida isolates were evaluated. C. albicans (61.6%) was still the predominant species in oral candidiasis patients with and without denture wearer, respectively, followed by C. glabrata (15.2%), C. tropicalis (10.4%), C. parapsilosis (3.2%), C. kefyr (3.6%), C. dubliniensis (2%), C. lusitaniae (2%), C. krusei (1.6%), and C. guilliermondii (0.4%). The proportion of mixed colonization with more than one Candida species was 18% from total cases. The relative CSH value and biofilm biomass of NAC species were greater than C. albicans (poral isolates NAC species had biofilm forming ability, whereas 78% of C. albicans were biofilm formers. Furthermore, the significant difference of relative CSH values between biofilm formers and non-biofilm formers was observed in the NAC species (poral cavity was gradually increasing. The possible contributing factors might be high cell surface hydrophobicity and biofilm forming ability. The relative CSH value could be a putative factor for determining biofilm formation ability of the non-albicans Candida species. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Effects of fluconazole treatment of mice infected with fluconazole-susceptible and -resistant Candida tropicalis on fungal cell surface hydrophobicity, adhesion and biofilm formation

    Directory of Open Access Journals (Sweden)

    R L Kanoshiki

    2015-01-01

    Full Text Available Background : The incidence of Candida tropicalis less susceptible to fluconazole (FLC has been reported in many parts of the world. Objectives : The aim of this study was to examine the changes of putative virulence attributes of Candida tropicalis accompanying the development of resistance to FLC in vitro and in vivo. Materials and Methods : A FLC-resistant strain (FLC-R was obtained after sequential exposure of a clinical isolate FLC-sensitive (FLC-S to increasing concentrations of the antifungal. The course of infection by both strains was analyzed in BALB/c mice. Analyses of gene expression were performed by real-time polymerase chain reaction PCR. The cell surface hydrophobicity, adhesion and biofilm formation were also determined. Results : Development of resistance to FLC could be observed after 15 days of subculture in azole-containing medium. Overexpression of MDR1 and ERG11 genes were observed in FLC-R, and this strain exhibited enhanced virulence in mice, as assessed by the mortality rate. All mice challenged with the FLC-R died and FLC-treatment caused earlier death in mice infected with this strain. All animals challenged with FLC-S survived the experiment, regardless of FLC-treatment. Overall, FLC-R derivatives strains were significantly more hydrophobic than FLC-S strains and showed greater adherence and higher capacity to form biofilm on polystyrene surface. Conclusions : The expression of virulence factors was higher in FLC-R-C. tropicalis and it was enhanced after FLC-exposure. These data alert us to the importance of identifying microorganisms that show resistance to the antifungals to establish an appropriate management of candidiasis therapy.

  14. Evolution of the lower planetary boundary layer over strongly contrasting surfaces

    International Nuclear Information System (INIS)

    Coulter, R.L.; Gao, W.; Martin, T.J.; Shannon, J.D.; Doran, J.C.; Hubbe, J.M.; Shaw, W.M.

    1992-01-01

    In a multilaboratory field study held near Boardman in northeastern Oregon in June 1991, various properties of the surface and lower atmospheric boundary layer over heavily irrigated cropland and adjacent desert steppe were investigated in the initial campaign of the Atmospheric Radiation Measurement (ARM) program. The locale was selected because its disparate characteristics over various spatial scales stress the ability of general circulation models (GCMS) to describe lower boundary conditions, particularly across the discontinuity between desert (in which turbulent flux of heat must be primarily as sensible heat) and large irrigated tracts (in which turbulent flux of latent heat should be the larger term). This campaign of ARM seeks to increase knowledge in three critical areas: (1) determination of the relationships between surface heat fluxes measured over multiple scales and the controlling surface parameters within each scale, (2) integration of local and nearly local heat flux estimates to produce estimates appropriate for GCM grid cells of 100-200 km horizontal dimension, and (3) characterization of the growth and development of the atmospheric boundary layer near transitions between surfaces with strongly contrasting moisture availabilities

  15. Proteolytic Degradation of Bovine Submaxillary Mucin (BSM) and Its Impact on Adsorption and Lubrication at a Hydrophobic Surface

    DEFF Research Database (Denmark)

    Madsen, Jan Busk; Svensson, Birte; Abou Hachem, Maher

    2015-01-01

    The effects of proteolytic digestion on bovinesubmaxillary mucin (BSM) were investigated in terms ofchanges in size, secondary structure, surface adsorption, and lubricating properties. Two proteases with distinctly different cleavage specificities, namely trypsin and pepsin, were employed. SDS...

  16. Modeling the effect of structural details of nonionic surfactant on micellization in solution and adsorption onto hydrophobic surfaces

    NARCIS (Netherlands)

    Jodar-Reyes, A.B.; Ortega-Vinuesa, J.L.; Martin-Rodriguez, A.; Leermakers, F.A.M.

    2002-01-01

    Applying the classical one-gradient self-consistent-field (SCF) theory for adsorption and/or association, we can show that the molecular architecture of nonionic surfactants influences strongly the micellization in solution and the adsorption on solid-liquid interfaces. This is illustrated by using

  17. Study of the Internal Flow and Evaporation Characteristic Inside a Water Droplet on a Vertical Vibrating Hydrophobic Surface

    Energy Technology Data Exchange (ETDEWEB)

    Park, Chang-Seok; Lim, Hee-Chang [Pusan Nat’l Univ., Busan (Korea, Republic of)

    2017-01-15

    Thermal Marangoni flow has been observed inside droplets on heated surfaces, finally resulting in a coffee stain effect. This study aims to visualize and control the thermal Marangoni flow by employing periodic vertical vibration. The variations in the contact angle and internal volume of the droplet as it evaporates is observed by using a combination of continuous light and a still camera. With regard to the internal velocity, the particle image velocimetry system is applied to visualize the internal thermal Marangoni flow. In order to estimate the internal temperature gradient and surface tension on the surface of a droplet, the theoretical model based on the conduction and convection theory of heat transfer is applied. Thus, the internal velocity increases with an increase in plate temperature. The flow directions of the Marangoni and gravitational flows are opposite, and hence, it may be possible to control the coffee stain effect.

  18. Lipoprotein hydrophobic core lipids are partially extruded to surface in smaller HDL: “Herniated” HDL, a common feature in diabetes

    Science.gov (United States)

    Amigó, Núria; Mallol, Roger; Heras, Mercedes; Martínez-Hervás, Sergio; Blanco-Vaca, Francisco; Escolà-Gil, Joan Carles; Plana, Núria; Yanes, Óscar; Masana, Lluís; Correig, Xavier

    2016-01-01

    Recent studies have shown that pharmacological increases in HDL cholesterol concentrations do not necessarily translate into clinical benefits for patients, raising concerns about its predictive value for cardiovascular events. Here we hypothesize that the size-modulated lipid distribution within HDL particles is compromised in metabolic disorders that have abnormal HDL particle sizes, such as type 2 diabetes mellitus (DM2). By using NMR spectroscopy combined with a biochemical volumetric model we determined the size and spatial lipid distribution of HDL subclasses in a cohort of 26 controls and 29 DM2 patients before and after two drug treatments, one with niacin plus laropiprant and another with fenofibrate as an add-on to simvastatin. We further characterized the HDL surface properties using atomic force microscopy and fluorescent probes to show an abnormal lipid distribution within smaller HDL particles, a subclass particularly enriched in the DM2 patients. The reduction in the size, force cholesterol esters and triglycerides to emerge from the HDL core to the surface, making the outer surface of HDL more hydrophobic. Interestingly, pharmacological interventions had no effect on this undesired configuration, which may explain the lack of clinical benefits in DM2 subjects. PMID:26778677

  19. A variant surface glycoprotein of Trypanosoma brucei is synthesized with a hydrophobic carboxy-terminal extension from purified glycoprotein.

    NARCIS (Netherlands)

    J.C. Boothroyd; G.A.M. Cross; J.H.J. Hoeijmakers (Jan); P. Borst (Piet)

    1980-01-01

    textabstractSequential expression of variant surface glycoproteins (VSGs) enables the parasitic protozoan Trypanosoma brucei to evade the immune response of its mammalian hosts. Studies of several VSGs, which have been isolated as soluble molecules following disruption of cells in the absence of

  20. Tribology and hydrophobicity of a biocompatible GPTMS/PFPE coating on Ti6Al4V surfaces.

    Science.gov (United States)

    Panjwani, Bharat; Sinha, Sujeet K

    2012-11-01

    Tribological properties of perfluoropolyether (PFPE) coated 3-glycidoxypropyltrimethoxy silane (GPTMS) SAMs (self-assembled monolayers) onto Ti6Al4V alloy substrate were studied using ball-on-disk experiments. GPTMS SAMs deposition onto a Ti6Al4V alloy surface was carried out using solution phase method. Ultra-thin layer of PFPE was dip-coated onto SAMs modified specimens. Tribological tests were carried out at 0.2 N normal load and rotational speed of 200 rpm using track radius of 2 mm. Wear track and counterface surface conditions were investigated using optical microscopy. PFPE modified specimens were baked at 150 °C for 1h to investigate the effect of thermal treatment on tribological properties. Surface characterization tests such as contact angle measurement, AFM morphology and X-ray photoelectron spectroscopy were carried out for differently modified specimens. PFPE overcoat meets the requirements of cytotoxicity test using the ISO 10993-5 elution method. PFPE top layer lowered the coefficient of friction and increased wear durability for different specimens (with and without GPTMS intermediate layer). PFPE overcoat onto GPTMS showed significant increase in the wear resistance compared with overcoat onto bare Ti6Al4V specimens. The observed improvement in the tribological properties can be attributed to the change in the interaction of PFPE molecules with the substrate surface due to the GPTMS intermediate layer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Measurements on hydrophobic and hydrophilic surfaces using a porous gamma alumina nanoparticle aggregate mounted on Atomic Force Microscopy cantilevers

    NARCIS (Netherlands)

    Das, Theerthankar; Becker, Thomas; Nair, Balagopal N.

    2010-01-01

    Atomic Force Microscopy (AFM) measurements are extensively used for a detailed understanding of molecular and surface forces. In this study, we present a technique for measuring such forces, using an AFM cantilever attached with a porous gamma alumina nanoparticle aggregate. The modified cantilever

  2. Transport of Dirac fermions on the surface of strong topological insulator and graphene

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Arijit

    2012-06-14

    In this dissertation I study electronic transport through Dirac Fermions on the surface of strong topological insulator and graphene. I start by reviewing the physics of topological insulator and graphene and the low energy effective theory for the electronic states of the surface of a 3D strong topological insulator and graphene. Using this theory the electronic structure of the surface states of strong topological insulators of geometries with large surface to bulk ratio like nanowire and thin film are obtained. Then the energy spectrum and the spin-parity structure of the eigenstates for a finite size topological insulator quantum dot of the shape of a nanotube are considered. Numerical calculations show that even at the lowest energy scales, the ''spin-surface locking'' is broken, that is, the spin direction in a topologically protected surface mode is not locked to the surface. The calculations also show the existence of ''zero-momentum'' modes, and sub-gap states localized near the ''caps'' of the dot. Both the energy spectrum and the spin texture of the eigenstates are basically reproduced from an analytical surface Dirac fermion description. The results are compared to microscopic calculations using a tight-binding model for a strong topological insulator in a finite-length nanowire geometry, which shows qualitative similarity. Then, a theoretical study of electron-phonon scattering effects in thin films made of a strong topological insulator is presented. Phonons are modeled by isotropic elastic continuum theory with stress-free boundary conditions, and the interaction with the helical surface Dirac fermions is mediated by the deformation potential. The temperature-dependent electrical resistivity ρ(T) and the quasi-particle decay rate Γ(T) observable in photo-emission are computed numerically. The low and high-temperature power laws for both quantities are obtained analytically. Detailed

  3. Scaling of turbulence spectra measured in strong shear flow near the Earth’s surface

    Science.gov (United States)

    Mikkelsen, T.; Larsen, S. E.; Jørgensen, H. E.; Astrup, P.; Larsén, X. G.

    2017-12-01

    Within the lowest kilometer of the Earth’s atmosphere, in the so-called atmospheric boundary layer, winds are often gusty and turbulent. Nearest to the ground, the turbulence is predominately generated by mechanical wall-bounded wind shear, whereas at higher altitudes turbulent mixing of heat and moisture also play a role. The variance (square of the standard deviation) of the fluctuation around the mean wind speed is a measure of the kinetic energy content of the turbulence. This kinetic energy can be resolved into the spectral distributions, or spectra, as functions of eddy size, wavenumber, or frequency. Spectra are derived from Fourier transforms of wind records as functions of space or time corresponding to wavenumber and frequency spectra, respectively. Atmospheric spectra often exhibit different subranges that can be distinguished and scaled by the physical parameters responsible for: (1) their generation; (2) the cascade of energy across the spectrum from large- to small-scale; and (3) the eventual decay of turbulence into heat owing to viscosity effects on the Kolmogorov microscale, in which the eddy size is only a fraction of a millimeter. This paper addresses atmospheric turbulence spectra in the lowest part of the atmospheric boundary layer—the so-called surface layer—where the wind shear is strong owing to the nonslip condition at the ground. Theoretical results dating back to Tchen’s early work in 1953 ‘on the spectrum of energy in turbulent shear flow’ led Tchen to predict a shear production subrange with a distinct inverse-linear power law for turbulence in a strongly sheared high-Reynolds number wall-bounded flow, as is encountered in the lowest sheared part of the atmospheric boundary layer, also known as the eddy surface layer. This paper presents observations of spectra measured in a meteorological mast at Høvsøre, Denmark, that support Tchen’s prediction of a shear production subrange following a distinct power law of degree

  4. Determination of functionalized gold nanoparticles incorporated in hydrophilic and hydrophobic microenvironments by surface modification of quartz crystal microbalance

    International Nuclear Information System (INIS)

    Wu, Tsui-Hsun; Liao, Shu-Chuan; Chen, Ying-Fang; Huang, Yi-You; Wei, Yi-Syuan; Tu, Shu-Ju; Chen, Ko-Shao

    2013-01-01

    In this study, plasma deposition methods were used to immobilize Au electrode of a quartz crystal microbalance (QCM) to create different microenvironments for mass measurement of various modified Au nanoparticles (AuNPs). AuNPs were modified by 11-mercaptoundecanoic acid (MUA) and 1-decanethiol (DCT) for potential applications to drug release, protective coatings, and immunosensors. We aimed to develop a highly sensitive and reliable method to quantify the mass of various modified AuNPs. The surface of AuNPs and Au electrode was coated with polymer films, as determined by Fourier transform infrared spectroscopy and atomic force microscopy. Measurements obtained for various AuNPs and the plasma-treated surface of the Au electrode were compared with those obtained for an untreated Au electrode. According to the resonant frequency shift of QCM, a linear relationship was observed that significantly differed for AuNPs, MUA-AuNPs, and DCT-AuNPs (R 2 range, 0.94–0.965, 0.934–0.972, and 0.874–0.9514, respectively). Compared to inductively coupled plasma and micro-computerized tomography, the QCM method with plasma treatment has advantages of real-time monitoring, greater sensitivity, and lower cost. Our results demonstrate that surface modifications measured by a QCM system for various modified AuNPs were reliable.

  5. Scaling of turbulence spectra measured in strong shear flow near the Earth’s surface

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Larsen, Søren Ejling; Ejsing Jørgensen, Hans

    2017-01-01

    Within the lowest kilometer of the Earth's atmosphere, in the so-called atmospheric boundary layer, winds are often gusty and turbulent. Nearest to the ground, the turbulence is predominately generated by mechanical wall-bounded wind shear, whereas at higher altitudes turbulent mixing of heat......) their generation; (2) the cascade of energy across the spectrum from large- to small-scale; and (3) the eventual decay of turbulence into heat owing to viscosity effects on the Kolmogorov microscale, in which the eddy size is only a fraction of a millimeter. This paper addresses atmospheric turbulence spectra...... in the lowest part of the atmospheric boundary layer—the so-called surface layer—where the wind shear is strong owing to the nonslip condition at the ground. Theoretical results dating back to Tchen's early work in 1953 'on the spectrum of energy in turbulent shear flow' led Tchen to predict a shear production...

  6. The Role of Hydrophobicity and Surface Receptors at Hyphae of Lyophyllum sp. Strain Karsten in the Interaction with Burkholderia terrae BS001 – Implications for Interactions in Soil

    Science.gov (United States)

    Vila, Taissa; Nazir, Rashid; Rozental, Sonia; dos Santos, Giulia M. P.; Calixto, Renata O. R.; Barreto-Bergter, Eliana; Wick, Lukas Y.; van Elsas, Jan Dirk

    2016-01-01

    The soil bacterium Burkholderia terrae strain BS001 can interact with varying soil fungi, using mechanisms that range from the utilization of carbon/energy sources such as glycerol to the ability to reach novel territories in soil via co-migration with growing fungal mycelia. Here, we investigate the intrinsic properties of the B. terrae BS001 interaction with the basidiomycetous soil fungus Lyophyllum sp. strain Karsten. In some experiments, the ascomycetous Trichoderma asperellum 302 was also used. The hyphae of Lyophyllum sp. strain Karsten were largely hydrophilic on water-containing media versus hydrophobic when aerial, as evidenced by contact angle analyses (CA). Co-migration of B. terrae strain BS001 cells with the hyphae of the two fungi occurred preferentially along the - presumably hydrophilic - soil-dwelling hyphae, whereas aerial hyphae did not allow efficient migration, due to reduced thickness of their surrounding mucous films. Moreover, the cell numbers over the length of the hyphae in soil showed an uneven distribution, i.e., the CFU numbers increased from minima at the inoculation point to maximal numbers in the middle of the extended hyphae, then decreasing toward the terminal side. Microscopic analyses of the strain BS001 associations with the Lyophyllum sp. strain Karsten hyphae in the microcosms confirmed the presence of B. terrae BS001 cells on the mucous matter that was present at the hyphal surfaces of the fungi used. Cell agglomerates were found to accumulate at defined sites on the hyphal surfaces, which were coined ‘fungal-interactive’ hot spots. Evidence was further obtained for the contention that receptors for a physical bacterium-fungus interaction occur at the Lyophyllum sp. strain Karsten hyphal surface, in which the specific glycosphingolipid ceramide monohexoside (CMH) plays an important role. Thus, bacterial adherence may be mediated by heterogeneously distributed fungal-specific receptors, implying the CMH moieties. This

  7. Continuum Lowering and Fermi-Surface Rising in Strongly Coupled and Degenerate Plasmas

    Science.gov (United States)

    Hu, S. X.

    2017-08-01

    Continuum lowering is a well known and important physics concept that describes the ionization potential depression (IPD) in plasmas caused by thermal- or pressure-induced ionization of outer-shell electrons. The existing IPD models are often used to characterize plasma conditions and to gauge opacity calculations. Recent precision measurements have revealed deficits in our understanding of continuum lowering in dense hot plasmas. However, these investigations have so far been limited to IPD in strongly coupled but nondegenerate plasmas. Here, we report a first-principles study of the K -edge shifting in both strongly coupled and fully degenerate carbon plasmas, with quantum molecular dynamics calculations based on the all-electron density-functional theory. The resulting K -edge shifting versus plasma density, as a probe to the continuum lowering and the Fermi-surface rising, is found to be significantly different from predictions of existing IPD models. In contrast, a simple model of "single-atom-in-box," developed in this work, accurately predicts K -edge locations as ab initio calculations provide.

  8. Investigating the effects of polymer molecular weight and non-solvent content on the phase separation, surface morphology and hydrophobicity of polyvinyl chloride films

    Science.gov (United States)

    Khoryani, Zahra; Seyfi, Javad; Nekoei, Mehdi

    2018-01-01

    The main aim of this research is to study the effects of polymer molecular weight as well as non-solvent concentration on the phase separation, surface morphology and wettability of polyvinyl chloride (PVC) films. Gel permeation chromatography (GPC) results showed that the Mn of the used PVC grades is 6 × 104, 8.7 × 104 and 1.26 × 105 g/mol. It was found that a proper combination of polymer molecular weight and non-solvent content could result in superhydrophobic and self-cleaning behaviors. Scanning electron microscopy (SEM) results demonstrated that addition of ethanol causes the polymer chains to be severely aggregated at the films' surface forming strand-like structures decorated by nano-scale polymer spheres. The polymer molecular weight was found to affect the degree of porosity which is highly influential on the hydrophobicity of the films. The mechanism of phase separation process was also discussed and it was found that the instantaneous demixing is the dominant mechanism once higher contents of non-solvent were used. However, a delayed demixing mechanism was detected when the lower molecular weight PVC has been used which resulted in a pore-less and dense skin layer. Differential scanning calorimetry was also utilized to study the crystallization and glass transition behavior of samples.

  9. An ellipsometry study on the effect of aluminium chloride and ferric chloride formulations on mucin layers adsorbed at hydrophobic surfaces.

    Science.gov (United States)

    Hamit-Eminovski, Jildiz; Eskilsson, Krister; Arnebrant, Thomas

    2010-07-01

    Ellipsometry was used to investigate the effect of polyaluminium chloride (PAC) formulations of different degrees of hydrolysation on an adsorbed mucin film. The results were compared to the effect of aluminium chloride (AlCl(3)) and ferric chloride. A compaction of the mucin film took place upon addition of the formulations and this occurred to different extents and at different concentrations for the different formulations. The compaction of PAC of a low degree of hydrolysis behaved similarly to AlCl(3). PAC of a high degree of hydrolysis showed a greater compaction effect than the other aluminium formulations. The initial compaction concentration was found to be 0.001 mM which is less than previously found for aluminium-mucin complex formation in bulk. The reversibility of the compaction was also investigated. The compaction of the mucin film was found to be partly reversible for AlCl(3) and PAC of low degree of hydrolysis. No reversibility was observed for the formulations of PAC of high hydrolysis grade or for ferric chloride. The results are consistent with previously observed effects of PAC of a low degree of hydrolysis on bacterial surfaces where a compaction of surface polymers was indicated by the reduced range of repulsive steric interactions.

  10. Experimental study of the Marangoni flow in evaporating water droplet placed on vertical vibration and heated hydrophobic surface

    Science.gov (United States)

    Park, Chang Seok; Lim, Hee Chang

    2015-11-01

    In general, the heated surface generates a Marangoni flow inside a droplet yielding a coffee stain effect in the end. This study aims to visualize and control the Marangoni flow by using periodic vertical vibration. While the droplet is evaporating, the variation of contact angle and internal volume of droplet was observed by using the combination of a continuous light and a DSLR still camera. Regarding the internal velocity, the PIV(Particle Image Velocimetry) system was applied to visualize the internal Marangoni flow. In order to estimate the temperature gradient inside and surface tension on the droplet, a commercial software Comsol Multiphysics was used. In the result, the internal velocity increases with the increase of the plate temperature and both flow directions of Marangoni and gravitational flow are opposite so that there seems to be a possibility to control the coffee stain effect. In addition, the Marangoni flow was controlled at relatively lower range of frequency 30 ~ 50Hz. Work supported by Korea government Ministry of Trade, Industry and Energy KETEP grant No. 20134030200290, Ministry of Education NRF grant No. NRF2013R1A1A2005347.

  11. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J. de; Polder, R.B.; Borsje, H.

    1998-01-01

    The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Several types of tests were carried out to study the performance of

  12. Hydrophobicity Tuning by the Fast Evolution of Mold Temperature during Injection Molding

    Directory of Open Access Journals (Sweden)

    Sara Liparoti

    2018-03-01

    Full Text Available The surface topography of a molded part strongly affects its functional properties, such as hydrophobicity, cleaning capabilities, adhesion, biological defense and frictional resistance. In this paper, the possibility to tune and increase the hydrophobicity of a molded polymeric part was explored. An isotactic polypropylene was injection molded with fast cavity surface temperature evolutions, obtained adopting a specifically designed heating system layered below the cavity surface. The surface topology was characterized by atomic force microscopy (AFM and, concerning of hydrophobicity, by measuring the water static contact angle. Results show that the hydrophobicity increases with both the temperature level and the time the cavity surface temperature was kept high. In particular, the contact angle of the molded sample was found to increase from 90°, with conventional molding conditions, up to 113° with 160 °C of cavity surface temperature kept for 18 s. This increase was found to be due to the presence of sub-micro and nano-structures characterized by high values of spatial frequencies which could be more accurately replicated by adopting high heating temperatures and times. The surface topography and the hydrophobicity resulted therefore tunable by selecting appropriate injection molding conditions.

  13. Liquid extraction surface analysis (LESA) of hydrophobic TLC plates coupled to chip-based nanoelectrospray high-resolution mass spectrometry.

    Science.gov (United States)

    Himmelsbach, Markus; Varesio, Emmanuel; Hopfgartner, Gérard

    2014-01-01

    Direct identification and structural characterization of analyte spots on TLC plates have always been of great interest and the development of interfaces that allow TLC to be combined with MS is making steady progress. The recently introduced liquid extraction surface analysis (LESA) approach has the potential to hyphenate TLC with MS. A mixture of lipid standards was separated on HPTLC RP-18 glass plates using chloroform:methanol :acetonitrile 2:1:1 (v:v:v) as mobile phase. After visualization with primuline dye (0.02% in acetone:water 8:2 (v:v)), LESA was performed, followed by a chip-based nanoflow infusion in combination with FTICRMS. The optimized extraction solvent composition was methanol:chloroform:water:formic acid 52:24:24:0.2 (v:v:v:v). A nanoelectrospray voltage of 1.6 kV and a gas pressure of 0.2 psi were applied in all experiments. All phospholipids were extracted successfully and detected unambiguously using the optimized TLC-LESA-FTICRMS procedure. Sampling the tricaprylin spot gave the most intense signals and also tricaprin was detected. Three other triacylglycerols of higher molecular mass have logP values between 15.5 and 21.6, which are the highest among all investigated compounds and are not detected from their corresponding spots, due to the fact that the solubility of very apolar lipids is not high enough in the extraction solvent. It was demonstrated that TLC can be elegantly combined with mass spectrometry based on the LESA approach. In general, apart from the analysis of lipids, TLC-LESA-MS has a high potential for medium-polar compounds separated on reversed-phase TLC plates, but limitations are present when very apolar compounds have to be extracted.

  14. Ethyl cellulose amphiphilic graft copolymers with LCST-UCST transition: Opposite self-assembly behavior, hydrophilic-hydrophobic surface and tunable crystalline morphologies.

    Science.gov (United States)

    Yuan, Hua; Chi, Hai; Yuan, Weizhong

    2016-08-20

    Novel and well-defined graft copolymer with block copolymer side chain, ethyl cellulose-graft-(poly(ε-caprolactone)-block-poly(N,N-dimethylaminoethylmeth acrylate)) (EC-g-(PCL-b-PDMAEMA)) with a lower critical solution temperature (LCST) was successfully synthesized via the combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). EC-g-(PCL-b-PDMAEMA) copolymers with various PCL-b-PDMAEMA block lengths were obtained by adjusting the molar ratios of the N,N-dimethylaminoethyl methacrylate monomer to ε-caprolactone. The EC-g-(PCL-b-PDMAPS) with an upper critical solution temperature (UCST) was obtained via facile quaternization reaction of PDMAEMA with 1,3-propane sultone. EC-g-(PCL-b-PDMAEMA) and EC-g-(PCL-b-PDMAPS) micelle solutions showed opposite thermoresponsiviness and hydrophilic-hydrophobic surface. Moreover, the tunable crystalline morphologies could be obtained from these graft copolymers through changing the polymer structure and PDMAEMA contents. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Confined surface plasmon sensors based on strongly coupled disk-in-volcano arrays.

    Science.gov (United States)

    Ai, Bin; Wang, Limin; Möhwald, Helmuth; Yu, Ye; Zhang, Gang

    2015-02-14

    Disk-in-volcano arrays are reported to greatly enhance the sensing performance due to strong coupling in the nanogaps between the nanovolcanos and nanodisks. The designed structure, which is composed of a nanovolcano array film and a disk in each cavity, is fabricated by a simple and efficient colloidal lithography method. By tuning structural parameters, the disk-in-volcano arrays show greatly enhanced resonances in the nanogaps formed by the disks and the inner wall of the volcanos. Therefore they respond to the surrounding environment with a sensitivity as high as 977 nm per RIU and with excellent linear dependence on the refraction index. Moreover, through mastering the fabrication process, biological sensing can be easily confined to the cavities of the nanovolcanos. The local responsivity has the advantages of maximum surface plasmon energy density in the nanogaps, reducing the sensing background and saving expensive reagents. The disk-in-volcano arrays also possess great potential in applications of optical and electrical trapping and single-molecule analysis, because they enable establishment of electric fields across the gaps.

  16. Strong uniaxial magnetic anisotropy in Co films on highly ordered grating-like nanopatterned Ge surfaces

    Science.gov (United States)

    Alam Mollick, Safiul; Singh, Ranveer; Kumar, Mohit; Bhattacharyya, Satyaranjan; Som, Tapobrata

    2018-03-01

    We present a systematic investigation on uniaxial magnetic anisotropy (UMA) in Co thin films induced by high aspect ratio nanopatterned anisotropic substrates. Self-organized long grating-like nanostructures, with extreme regularities, are fabricated on Ge surfaces using Au-ion implantation at room temperature. Subsequently deposition of Co films are carried out on the same at two different angles. Magneto-optical Kerr effect measurements show strong UMA in Co films grown on ion-patterned Ge substrates, fabricated under different ion fluences, along and perpendicular to the direction of the patterns (long grating-like nanostructures). Magnetic force microscopy measurements under different externally applied magnetic fields reveal an easy domain wall motion when the field is applied along the grating-like nanostructures. On the other hand, high amplitude grating-like nanostructures hinder the spin rotation when the field is applied along the hard axis. The present study will be useful for magnetic recording media and ultra-small magnetic field sensors.

  17. A comparative study of surface waves inversion techniques at strong motion recording sites in Greece

    Science.gov (United States)

    Panagiotis C. Pelekis,; Savvaidis, Alexandros; Kayen, Robert E.; Vlachakis, Vasileios S.; Athanasopoulos, George A.

    2015-01-01

    Surface wave method was used for the estimation of Vs vs depth profile at 10 strong motion stations in Greece. The dispersion data were obtained by SASW method, utilizing a pair of electromechanical harmonic-wave source (shakers) or a random source (drop weight). In this study, three inversion techniques were used a) a recently proposed Simplified Inversion Method (SIM), b) an inversion technique based on a neighborhood algorithm (NA) which allows the incorporation of a priori information regarding the subsurface structure parameters, and c) Occam's inversion algorithm. For each site constant value of Poisson's ratio was assumed (ν=0.4) since the objective of the current study is the comparison of the three inversion schemes regardless the uncertainties resulting due to the lack of geotechnical data. A penalty function was introduced to quantify the deviations of the derived Vs profiles. The Vs models are compared as of Vs(z), Vs30 and EC8 soil category, in order to show the insignificance of the existing variations. The comparison results showed that the average variation of SIM profiles is 9% and 4.9% comparing with NA and Occam's profiles respectively whilst the average difference of Vs30 values obtained from SIM is 7.4% and 5.0% compared with NA and Occam's.

  18. Elastic and viscous bond components in the adhesion of colloidal particles and fibrillated streptococci to QCM-D crystal surfaces with different hydrophobicities using Kelvin-Voigt and Maxwell models.

    Science.gov (United States)

    van der Westen, Rebecca; Sharma, Prashant K; De Raedt, Hans; Vermue, Ijsbrand; van der Mei, Henny C; Busscher, Henk J

    2017-09-27

    A quartz-crystal-microbalance with dissipation (QCM-D) can measure molecular mass adsorption as well as register adhesion of colloidal particles. However, analysis of the QCM-D output to quantitatively analyze adhesion of (bio)colloids to obtain viscoelastic bond properties is still a subject of debate. Here, we analyze the QCM-D output to analyze the bond between two hydrophilic streptococcal strains 91 nm long and without fibrillar surface appendages and micron-sized hydrophobic polystyrene particles on QCM-D crystal surfaces with different hydrophobicities, using the Kelvin-Voigt model and the Maxwell model. A Poisson distribution was implemented in order to determine the possible virtues of including polydispersity when fitting model parameters to the data. The quality of the fits did not indicate whether the Kelvin-Voigt or the Maxwell model is preferable and only polydispersity in spring-constants improved the fit for polystyrene particles. The Kelvin-Voigt and Maxwell models both yielded higher spring-constants for the bald streptococcus than for the fibrillated one. In both models, the drag coefficients increased for the bald streptococcus with the ratio of electron-donating over electron-accepting parameters of the crystal surface, while for the fibrillated strain the drag coefficient was similar on all crystal surfaces. Combined with the propensity of fibrillated streptococci to bind to the sensor crystal as a coupled-resonator above the crystal surface, this suggests that the drag experienced by resonator-coupled, hydrophilic particles is more influenced by the viscosity of the bulk water than by interfacial water adjacent to the crystal surface. Hydrophilic particles that lack a surface tether are mass-coupled just above the crystal surface and accordingly probe the drag due to the thin layer of interfacial water that is differently structured on hydrophobic and hydrophilic surfaces. Hydrophobic particles without a surface tether are also mass

  19. Multivariate analysis of hydrophobic descriptors

    Directory of Open Access Journals (Sweden)

    Stefan Dove

    2014-04-01

    Full Text Available Multivariate approaches like principal component analysis (PCA are powerful tools to investigate hydrophobic descriptors and to discriminate between intrinsic hydrophobicity and polar contributions as hydrogen bonds and other electronic effects. PCA of log P values measured for 37 solutes in eight solvent-water systems and of hydrophobic octanol-water substituent constants p for 25 meta- and para-substituents from seven phenyl series were performed (re-analysis of previous work. In both cases, the descriptors are repro­duced within experimental errors by two principal components, an intrinsic hydrophobic component and a second component accounting for differences between the systems due to electronic interactions. Underlying effects were identified by multiple linear regression analysis. Log P values depend on the water solubility of the solvents and hydrogen bonding capabilities of both the solute and the solvents. Results indicate different impacts of hydrogen bonds in nonpolar and polar solvent-water systems on log P and their dependence on isotropic and hydrated surface areas. In case of the p-values, the second component (loadings and scores correlates with electronic substituent constants. More detailed analysis of the data as p-values of disubstituted benzenes XPhY has led to extended symmetric bilinear Hammett-type models relating interaction increments to cross products pX sY, pY sX and sX sY which are mainly due to mutual effects on hydrogen-bonds with octanol.

  20. Surface wave site characterization at 27 locations near Boston, Massachusetts, including 2 strong-motion stations

    Science.gov (United States)

    Thompson, Eric M.; Carkin, Bradley A.; Baise, Laurie G.; Kayen, Robert E.

    2014-01-01

    The geotechnical properties of the soils in and around Boston, Massachusetts, have been extensively studied. This is partly due to the importance of the Boston Blue Clay and the extent of landfill in the Boston area. Although New England is not a region that is typically associated with seismic hazards, there have been several historical earthquakes that have caused significant ground shaking (for example, see Street and Lacroix, 1979; Ebel, 1996; Ebel, 2006). The possibility of strong ground shaking, along with heightened vulnerability from unreinforced masonry buildings, motivates further investigation of seismic hazards throughout New England. Important studies that are pertinent to seismic hazards in New England include source-parameter studies (Somerville and others, 1987; Boore and others, 2010), wave-propagation studies (Frankel, 1991; Viegas and others, 2010), empirical ground-motion prediction equations (GMPE) for computing ground-motion intensity (Tavakoli and Pezeshk, 2005; Atkinson and Boore, 2006), site-response studies (Hayles and others, 2001; Ebel and Kim, 2006), and liquefaction studies (Brankman and Baise, 2008). The shear-wave velocity (VS) profiles collected for this report are pertinent to the GMPE, site response, and liquefaction aspects of seismic hazards in the greater Boston area. Besides the application of these data for the Boston region, the data may be applicable throughout New England, through correlations with geologic units (similar to Ebel and Kim, 2006) or correlations with topographic slope (Wald and Allen, 2007), because few VS measurements are available in stable tectonic regions.Ebel and Hart (2001) used felt earthquake reports to infer amplification patterns throughout the greater Boston region and noted spatial correspondence with the dominant period and amplification factors obtained from ambient noise (horizontal-to-vertical ratios) by Kummer (1998). Britton (2003) compiled geotechnical borings in the area and produced a

  1. A method for detecting hydrophobic patches protein

    NARCIS (Netherlands)

    Lijnzaad, P.; Berendsen, H.J.C.; Argos, P.

    1996-01-01

    A method for the detection of hydrophobic patches on the surfaces of protein tertiary structures is presented, it delineates explicit contiguous pieces of surface of arbitrary size and shape that consist solely of carbon and sulphur atoms using a dot representation of the solvent-accessible surface,

  2. Super-hydrophobic fluorine containing aerogels

    Science.gov (United States)

    Coronado, Paul R [Livermore, CA; Poco, John F [Livermore, CA; Hrubesh, Lawrence W [Pleasanton, CA

    2007-05-01

    An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.

  3. Evaporation rate of water in hydrophobic confinement.

    Science.gov (United States)

    Sharma, Sumit; Debenedetti, Pablo G

    2012-03-20

    The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 Å and surface areas between 1 and 9 nm(2)), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 Å. The computed free energy barriers are of the order of 50 kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm(2)) than by the smaller (1 nm(2)) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube.

  4. Water interaction with hydrophobic and hydrophilic soot particles.

    Science.gov (United States)

    Popovicheva, Olga; Persiantseva, Natalia M; Shonija, Natalia K; DeMott, Paul; Koehler, Kirsten; Petters, Markus; Kreidenweis, Sonia; Tishkova, Victoria; Demirdjian, Benjamin; Suzanne, Jean

    2008-05-07

    The interaction of water with laboratory soots possessing a range of properties relevant for atmospheric studies is examined by two complementary methods: gravimetrical measurement of water uptake coupled with chemical composition and porosity analysis and HTDMA (humidified tandem differential mobility analyzer) inference of water uptake accompanied by separate TEM (transmission electron microscopy) analysis of single particles. The first method clarifies the mechanism of water uptake for bulk soot and allows the classification of soot with respect to its hygroscopicity. The second method highlights the dependence of the soot aerosol growth factor on relative humidity (RH) for quasi-monodisperse particles. Hydrophobic and hydrophilic soot are qualitatively defined by their water uptake and surface polarity: laboratory soot particles are thus classified from very hydrophobic to very hydrophilic. Thermal soot particles produced from natural gas combustion are classified as hydrophobic with a surface of low polarity since water is found to cover only half of the surface. Graphitized thermal soot particles are proposed for comparison as extremely hydrophobic and of very low surface polarity. Soot particles produced from laboratory flame of TC1 aviation kerosene are less hydrophobic, with their entire surface being available for statistical monolayer water coverage at RH approximately 10%. Porosity measurements suggest that, initially, much of this surface water resides within micropores. Consequently, the growth factor increase of these particles to 1.07 at RH > 80% is attributed to irreversible swelling that accompanies water uptake. Hysteresis of adsorption/desorption cycles strongly supports this conclusion. In contrast, aircraft engine soot, produced from burning TC1 kerosene in a gas turbine engine combustor, has an extremely hydrophilic surface of high polarity. Due to the presence of water soluble organic and inorganic material it can be covered by many water

  5. Study of the grazing-incidence X-ray scattering of strongly disturbed fractal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Roshchin, B. S., E-mail: ross@crys.ras.ru; Chukhovsky, F. N.; Pavlyuk, M. D.; Opolchentsev, A. M.; Asadchikov, V. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Centre “Crystallography and Photonics” (Russian Federation)

    2017-03-15

    The applicability of different approaches to the description of hard X-ray scattering from rough surfaces is generally limited by a maximum surface roughness height of no more than 1 nm. Meanwhile, this value is several times larger for the surfaces of different materials subjected to treatment, especially in the initial treatment stages. To control the roughness parameters in all stages of surface treatment, a new approach has been developed, which is based on a series expansion of wavefield over the plane eigenstate-function waves describing the small-angle scattering of incident X-rays in terms of plane q-waves propagating through the interface between two media with a random function of relief heights. To determine the amplitudes of reflected and transmitted plane q-waves, a system of two linked integral equations was derived. The solutions to these equations correspond (in zero order) to the well-known Fresnel expressions for a smooth plane interface. Based on these solutions, a statistical fractal model of an isotropic rough interface is built in terms of root-mean-square roughness σ, two-point correlation length l, and fractal surface index h. The model is used to interpret X-ray scattering data for polished surfaces of single-crystal cadmium telluride samples.

  6. On eigenvalue asymptotics for strong delta-interactions supported by surfaces with boundaries

    Czech Academy of Sciences Publication Activity Database

    Dittrich, Jaroslav; Exner, Pavel; Kuhn, C.; Pankrashkin, K.

    2016-01-01

    Roč. 97, 1-2 (2016), s. 1-25 ISSN 0921-7134 R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : singular Schrodinger operator * delta-interaction * strong coupling * eigenvalue Subject RIV: BE - Theoretical Physics Impact factor: 0.933, year: 2016

  7. Increasing prion propensity by hydrophobic insertion.

    Directory of Open Access Journals (Sweden)

    Aaron C Gonzalez Nelson

    Full Text Available Prion formation involves the conversion of proteins from a soluble form into an infectious amyloid form. Most yeast prion proteins contain glutamine/asparagine-rich regions that are responsible for prion aggregation. Prion formation by these domains is driven primarily by amino acid composition, not primary sequence, yet there is a surprising disconnect between the amino acids thought to have the highest aggregation propensity and those that are actually found in yeast prion domains. Specifically, a recent mutagenic screen suggested that both aromatic and non-aromatic hydrophobic residues strongly promote prion formation. However, while aromatic residues are common in yeast prion domains, non-aromatic hydrophobic residues are strongly under-represented. Here, we directly test the effects of hydrophobic and aromatic residues on prion formation. Remarkably, we found that insertion of as few as two hydrophobic residues resulted in a multiple orders-of-magnitude increase in prion formation, and significant acceleration of in vitro amyloid formation. Thus, insertion or deletion of hydrophobic residues provides a simple tool to control the prion activity of a protein. These data, combined with bioinformatics analysis, suggest a limit on the number of strongly prion-promoting residues tolerated in glutamine/asparagine-rich domains. This limit may explain the under-representation of non-aromatic hydrophobic residues in yeast prion domains. Prion activity requires not only that a protein be able to form prion fibers, but also that these fibers be cleaved to generate new independently-segregating aggregates to offset dilution by cell division. Recent studies suggest that aromatic residues, but not non-aromatic hydrophobic residues, support the fiber cleavage step. Therefore, we propose that while both aromatic and non-aromatic hydrophobic residues promote prion formation, aromatic residues are favored in yeast prion domains because they serve a dual

  8. Age of oil palm plantations causes a strong change in surface biophysical variables

    Science.gov (United States)

    Sabajo, Clifton; le Maire, Guerric; Knohl, Alexander

    2016-04-01

    Over the last decades, Indonesia has experienced dramatic land transformations with an expansion of oil palm plantations at the expense of tropical forests. As vegetation is a modifier of the climate near the ground these large-scale land transformations are expected to have major impacts on the surface biophysical variables i.e. surface temperature, albedo, and vegetation indices, e.g. the NDVI. Remote sensing data are needed to assess such changes at regional scale. We used 2 Landsat images from Jambi Province in Sumatra/Indonesia covering a chronosequence of oil palm plantations to study the 20 - 25 years life cycle of oil palm plantations and its relation with biophysical variables. Our results show large differences between the surface temperature of young oil palm plantations and forest (up to 9.5 ± 1.5 °C) indicating that the surface temperature is raised substantially after the establishment of oil palm plantations following the removal of forests. During the oil palm plantation lifecycle the surface temperature differences gradually decreases and approaches zero around an oil palm plantation age of 10 years. Similarly, NDVI increases and the albedo decreases approaching typical values of forests. Our results show that in order to assess the full climate effects of oil palm expansion biophysical processes play an important role and the full life cycle of oil palm plantations need to be considered.

  9. Heat-resistant hydrophobic-oleophobic coatings

    OpenAIRE

    Uyanik, Mehmet; Arpac, Ertugrul; Schmidt, Helmut K.; Akarsu, Murat; Sayilkan, Funda; Sayilkan, Hikmet

    2006-01-01

    Thermally and chemically durable hydrophobic oleophobic coatings, containing different ceramic particles such as SiO2, SiC, Al 2O3, which can be alternative instead of Teflon, have been developed and applied on the aluminum substrates by spin-coating method. Polyimides, which are high-thermal resistant heteroaromatic polymers, were synthesized, and fluor oligomers were added to these polymers to obtain hydrophobic-oleophobic properties. After coating, Al surface was subjected to Taber-abrasio...

  10. Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States.

    Science.gov (United States)

    Bentmann, H; Maaß, H; Krasovskii, E E; Peixoto, T R F; Seibel, C; Leandersson, M; Balasubramanian, T; Reinert, F

    2017-09-08

    A comprehensive understanding of spin-polarized photoemission is crucial for accessing the electronic structure of spin-orbit coupled materials. Yet, the impact of the final state in the photoemission process on the photoelectron spin has been difficult to assess in these systems. We present experiments for the spin-orbit split states in a Bi-Ag surface alloy showing that the alteration of the final state with energy may cause a complete reversal of the photoelectron spin polarization. We explain the effect on the basis of ab initio one-step photoemission theory and describe how it originates from linear dichroism in the angular distribution of photoelectrons. Our analysis shows that the modulated photoelectron spin polarization reflects the intrinsic spin density of the surface state being sampled differently depending on the final state, and it indicates linear dichroism as a natural probe of spin-orbit coupling at surfaces.

  11. Strong and tough cellulose nanopaper with high specific surface area and porosity.

    Science.gov (United States)

    Sehaqui, Houssine; Zhou, Qi; Ikkala, Olli; Berglund, Lars A

    2011-10-10

    In order to better understand nanostructured fiber networks, effects from high specific surface area of nanofibers are important to explore. For cellulose networks, this has so far only been achieved in nonfibrous regenerated cellulose aerogels. Here, nanofibrillated cellulose (NFC) is used to prepare high surface area nanopaper structures, and the mechanical properties are measured in tensile tests. The water in NFC hydrogels is exchanged to liquid CO2, supercritical CO2, and tert-butanol, followed by evaporation, supercritical drying, and sublimation, respectively. The porosity range is 40-86%. The nanofiber network structure in nanopaper is characterized by FE-SEM and nitrogen adsorption, and specific surface area is determined. High-porosity TEMPO-oxidized NFC nanopaper (56% porosity) prepared by critical point drying has a specific surface area as high as 482 m(2) g(-1). The mechanical properties of this nanopaper structure are better than for many thermoplastics, but at a significantly lower density of only 640 kg m(-3). The modulus is 1.4 GPa, tensile strength 84 MPa, and strain-to-failure 17%. Compared with water-dried nanopaper, the material is softer with substantiallly different deformation behavior.

  12. Prediction of strong earthquake motions on rock surface using evolutionary process models

    International Nuclear Information System (INIS)

    Kameda, H.; Sugito, M.

    1984-01-01

    Stochastic process models are developed for prediction of strong earthquake motions for engineering design purposes. Earthquake motions with nonstationary frequency content are modeled by using the concept of evolutionary processes. Discussion is focused on the earthquake motions on bed rocks which are important for construction of nuclear power plants in seismic regions. On this basis, two earthquake motion prediction models are developed, one (EMP-IB Model) for prediction with given magnitude and epicentral distance, and the other (EMP-IIB Model) to account for the successive fault ruptures and the site location relative to the fault of great earthquakes. (Author) [pt

  13. Definition and display of steric, hydrophobic, and hydrogen-bonding properties of ligand binding sites in proteins using Lee and Richards accessible surface: validation of a high-resolution graphical tool for drug design.

    Science.gov (United States)

    Bohacek, R S; McMartin, C

    1992-05-15

    The accessible surface, described by Lee and Richards (the L&R surface: J. Mol. Biol. 1971, 55, 379), has remarkably useful properties for displaying ligand-protein interactions. The surface is placed one van der Waals radius plus one probe radius away from the protein atoms. The ligands are displayed in skeletal form. With a suitable probe radius, those parts of the ligand in good van der Waals contact with the protein binding site are found superimposed on the L&R surface. Display of the surface using parallel contours therefore provides a very powerful guide for interactive drug design because only ligand atoms lying on or close to the surface are in low-energy contact. The ability of the surface to accurately display steric complementarity between ligands and proteins was optimized using data from small molecule crystal structures. The possibility of displaying the chemical specificity of the binding site was also investigated. The surface can be colored to give precise information about chemical specificity. Electrostatic potential, electrostatic gradient, and distance to hydrogen-bonding groups were tested as methods of displaying chemical specificity. The ability of these methods to describe the complementarity actually observed in the interior of proteins was compared. High-resolution crystal data for ribonuclease and trypsin was used. The environment surrounding extended peptide chains in the protein was treated as a virtual binding site. The peptide chain served as a virtual ligand. This large sample of experimental data was used to measure the correlation between type of ligand atom and the calculated property of the nearest binding site surface. The best correlation was obtained using hydrogen-bonding properties of the binding site. Using this parameter the surface could be divided into three separate zones representing the hydrophobic, hydrogen-bond-acceptor, and hydrogen-bond-donor properties of the binding site. The percentage of hydrophobic ligand

  14. Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces

    Science.gov (United States)

    Iliev, Stanimir; Pesheva, Nina

    2016-06-01

    We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1 -0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012), 10.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

  15. Surface Nanostructures Formed by Phase Separation of Metal Salt-Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications

    Science.gov (United States)

    Con, Celal; Cui, Bo

    2017-12-01

    This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt-polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.

  16. Experimental study on the flow/ heat transfer performance of micro-scale pin fin coating with super-hydrophobic surface adding Nano particle

    Science.gov (United States)

    Hua, Junye; Duan, Yuanyuan; Li, Gui; Xu, Qiong; Li, Dong; Wu, Wei; Zhao, Xiaobao; Qiu, Delai

    2018-02-01

    The experimental studies on heat transfer and flow resistance characteristics of ellipse-shape micro pin fin have been conducted which is drafted with hydrophobic material, holding the various contact angles fulfilled by adjusting the amount of Nano particle. The results show that with the increases of contact angle(83°,99.5°, 119.5°and 151.5°), the bottom wall temperature rises under the same flow rate. Under a certain heating condition with heating power as 100 W, the average convective heat transfer coefficient decreases with the increase of contact angle with the same Re. The value of Nu for ellipse-shape micro pin fin increases with a higher Re, with the maximum value under experimental condition of Nu as 25. Besides, the friction coefficient of micro pin fin experimental section drafted hydrophobicity treatment significantly decreases, compared with the smooth micro pin fin experimental section (θ = 83°). While the higher contact angle has obvious positive influences on friction coefficient under the same Re. Generally, the flow resistance performance of ellipse-shape micro pin fin drafted with hydrophobic material is better than that without any treatment.

  17. Exchange interaction of strongly anisotropic tripodal erbium single-ion magnets with metallic surfaces

    DEFF Research Database (Denmark)

    Dreiser, Jan; Wäckerlin, Christian; Ali, Md. Ehesan

    2014-01-01

    We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed....... Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD M(H) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals...

  18. Drops on hydrophobic surfaces & vibrated fluid surfaces

    DEFF Research Database (Denmark)

    Wind-Willassen, Øistein

    of a droplet is then given, after which we set up a 2D computational Finite-Element Method (FEM) model for a neutrally buoyant drop immersed in another liquid. The model is validated by considering the volume loss over time. Subsequent to an introduction to the physics of wetting, the developed FEM model......-leap dynamics, exotic trajectories and the emergence of statistical behavior when the forcing is near the Faraday threshold....

  19. Hydrophobicity of carbohydrates and related hydroxy compounds.

    Science.gov (United States)

    Buttersack, Christoph

    2017-06-29

    The hydrophobic interaction of carbohydrates and other hydroxy compounds with a C18-modified silica gel column was measured with pure water as eluent, thereby expanding the range of measurements already published. The interaction is augmented by structure strengthening salts and decreasing temperature. Although the interaction of the solute with the hydrophobic interface is expected to only imperfectly reflect its state in aqueous bulk solution, the retention can be correlated to hydration numbers calculated from molecular mechanics studies given in the literature. No correlation can be established towards published hydration numbers obtained by physical methods (isentropic compressibility, O-17 NMR relaxation, terahertz spectroscopy, and viscosity). The hydrophobicity is discussed with respect to the chemical structure. It increases with the fraction and size of hydrophobic molecular surface regions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Highly tunable hybrid metamaterials employing split-ring resonators strongly coupled to graphene surface plasmons

    Science.gov (United States)

    Liu, Peter Q.; Luxmoore, Isaac J.; Mikhailov, Sergey A.; Savostianova, Nadja A.; Valmorra, Federico; Faist, Jérôme; Nash, Geoffrey R.

    2015-01-01

    Metamaterials and plasmonics are powerful tools for unconventional manipulation and harnessing of light. Metamaterials can be engineered to possess intriguing properties lacking in natural materials, such as negative refractive index. Plasmonics offers capabilities of confining light in subwavelength dimensions and enhancing light–matter interactions. Recently, the technological potential of graphene-based plasmonics has been recognized as the latter features large tunability, higher field-confinement and lower loss compared with metal-based plasmonics. Here, we introduce hybrid structures comprising graphene plasmonic resonators coupled to conventional split-ring resonators, thus demonstrating a type of highly tunable metamaterial, where the interaction between the two resonances reaches the strong-coupling regime. Such hybrid metamaterials are employed as high-speed THz modulators, exhibiting ∼60% transmission modulation and operating speed in excess of 40 MHz. This device concept also provides a platform for exploring cavity-enhanced light–matter interactions and optical processes in graphene plasmonic structures for applications including sensing, photo-detection and nonlinear frequency generation. PMID:26584781

  1. Highly tunable hybrid metamaterials employing split-ring resonators strongly coupled to graphene surface plasmons

    Science.gov (United States)

    Liu, Peter Q.; Luxmoore, Isaac J.; Mikhailov, Sergey A.; Savostianova, Nadja A.; Valmorra, Federico; Faist, Jérôme; Nash, Geoffrey R.

    2015-11-01

    Metamaterials and plasmonics are powerful tools for unconventional manipulation and harnessing of light. Metamaterials can be engineered to possess intriguing properties lacking in natural materials, such as negative refractive index. Plasmonics offers capabilities of confining light in subwavelength dimensions and enhancing light-matter interactions. Recently, the technological potential of graphene-based plasmonics has been recognized as the latter features large tunability, higher field-confinement and lower loss compared with metal-based plasmonics. Here, we introduce hybrid structures comprising graphene plasmonic resonators coupled to conventional split-ring resonators, thus demonstrating a type of highly tunable metamaterial, where the interaction between the two resonances reaches the strong-coupling regime. Such hybrid metamaterials are employed as high-speed THz modulators, exhibiting ~60% transmission modulation and operating speed in excess of 40 MHz. This device concept also provides a platform for exploring cavity-enhanced light-matter interactions and optical processes in graphene plasmonic structures for applications including sensing, photo-detection and nonlinear frequency generation.

  2. Probing Sub-GeV Mass Strongly Interacting Dark Matter with a Low-Threshold Surface Experiment.

    Science.gov (United States)

    Davis, Jonathan H

    2017-11-24

    Using data from the ν-cleus detector, based on the surface of Earth, we place constraints on dark matter in the form of strongly interacting massive particles (SIMPs) which interact with nucleons via nuclear-scale cross sections. For large SIMP-nucleon cross sections, the sensitivity of traditional direct dark matter searches using underground experiments is limited by the energy loss experienced by SIMPs, due to scattering with the rock overburden and experimental shielding on their way to the detector apparatus. Hence, a surface-based experiment is ideal for a SIMP search, despite the much larger background resulting from the lack of shielding. We show using data from a recent surface run of a low-threshold cryogenic detector that values of the SIMP-nucleon cross section up to approximately 10^{-27}  cm^{2} can be excluded for SIMPs with masses above 100 MeV.

  3. Solvent fluctuations at hydrophobic, hydrophilic, and electrochemical interfaces

    Science.gov (United States)

    Willard, Adam Phillip

    Using both coarse grained and atomistic models we study the behavior of water at the hydrophobic, hydrophilic and electrochemical interface. We show that the structural and fluxional properties of the water-solute interface are much different for small hydrophobic solutes than for large hydrophobic solutes. In the former case the solute is accommodated within the bulk hydrogen bonding network and interfacial properties are governed by the preservation of this network. In the latter case the solute-solvent interface forms what is akin to an ordinary water-vapor interface which is reflected in the interfacial properties. We examine the effect of introducing dispersive-like solute-solvent attractive interactions and find that the interface of a small hydrophobic solute is only slightly susceptible to the magnitude of solute-solvent attractions. We find that although the fluctuations of the large hydrophobic solute-solvent interface depend strongly on the magnitude of the solute-solvent attraction, the inherent structure of the liquid-vapor-like interface is insensitive to the magnitude of the solute-solvent attraction. In a separate analysis we use coarse-grained models to investigate the behavior of water adjacent to an extended hydrophobic surface peppered with various fractions of hydrophilic patches of different sizes. We study the spatial dependence of the mean interface height, the solvent density fluctuations related to drying the patchy substrate, and the spatial dependence of interfacial fluctuations. We find that adding small uniform attractive interactions between the substrate and solvent cause the mean position of the interface to be very close to the substrate. Nevertheless, the interfacial fluctuations are large and spatially heterogeneous in response to the underlying patchy substrate. We discuss the implications of these findings for the assembly of heterogeneous surfaces. We also use a coarse-grained solvent model to study the self-assembly of two

  4. Stick-Jump (SJ) Evaporation of Strongly Pinned Nanoliter Volume Sessile Water Droplets on Quick Drying, Micropatterned Surfaces.

    Science.gov (United States)

    Debuisson, Damien; Merlen, Alain; Senez, Vincent; Arscott, Steve

    2016-03-22

    We present an experimental study of stick-jump (SJ) evaporation of strongly pinned nanoliter volume sessile water droplets drying on micropatterned surfaces. The evaporation is studied on surfaces composed of photolithographically micropatterned negative photoresist (SU-8). The micropatterning of the SU-8 enables circular, smooth, trough-like features to be formed which causes a very strong pinning of the three phase (liquid-vapor-solid) contact line of an evaporating droplet. This is ideal for studying SJ evaporation as it contains sequential constant contact radius (CCR) evaporation phases during droplet evaporation. The evaporation was studied in nonconfined conditions, and forced convection was not used. Micropatterned concentric circles were defined having an initial radius of 1000 μm decreasing by a spacing ranging from 500 to 50 μm. The droplet evaporates, successively pinning and depinning from circle to circle. For each pinning radius, the droplet contact angle and volume are observed to decrease quasi-linearly with time. The experimental average evaporation rates were found to decrease with decreasing pining radii. In contrast, the experimental average evaporation flux is found to increase with decreasing droplet radii. The data also demonstrate the influence of the initial contact angle on evaporation rate and flux. The data indicate that the total evaporation time of a droplet depends on the specific micropattern spacing and that the total evaporation time on micropatterned surfaces is always less than on flat, homogeneous surfaces. Although the surface patterning is observed to have little effect on the average droplet flux-indicating that the underlying evaporation physics is not significantly changed by the patterning-the total evaporation time is considerably modified by patterning, up to a factor or almost 2 compared to evaporation on a flat, homogeneous surface. The closely spaced concentric circle pinning maintains a large droplet radius and

  5. Corrosion protection of reinforcement by hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Polder, R.B.; Vries, H. de

    1999-01-01

    Penetration of de-icing salts into concrete bridge decks may cause corrosion of reinforcement. Hydrophobic treatment of concrete was studied as additional protection. It was shown that hydrophobic treatment strongly reduces chloride ingress, during semi-permanent contact and in wetting/drying

  6. Prevention of reinforcement corrosion by hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Polder, R.B.; Borsje, H.; Vries, H. de

    2001-01-01

    Corrosion of reinforcement in concrete bridge decks may occur due to penetration of de-icing salts, even in the presence of an asphalt overlay. This paper reports a laboratory study into additional protection of concrete by hydrophobic treatment. It was found that hydrophobic treatment strongly

  7. Personally committed to emotional labor: Surface acting, emotional exhaustion and performance among service employees with a strong need to belong.

    Science.gov (United States)

    Yagil, Dana; Medler-Liraz, Hana

    2017-10-01

    Individual differences in emotional labor and subsequent vulnerability to burnout have been explored through the prism of Congruence Theory, which examines the congruence between personality traits and job requirements (Bono & Vey, 2007; Moskowitz & Coté, 1995). Drawing on theory and research dealing with the association between the need to belong and self-regulation (Baumeister, DeWall, Ciarocco & Twenge, 2005), this study examined the relationship between need to belong and service employees' surface acting and associated outcomes. In Study 1, participants (N = 54) were asked to write a response to an aggressive email from a hypothetical customer. The need to belong was positively related to display of positive emotions and negatively to display of negative emotions in the responses, but not related to felt anger, suggesting that it is associated with the inclination to engage in surface acting. In Study 2, a field study conducted with 170 service employee-customer dyads, surface acting mediated the positive relationship between fear of isolation and emotional exhaustion, and emotional exhaustion mediated the relationship between surface acting and customer satisfaction. These results suggested that service employees with a strong need to belong might have a heightened risk of burnout because of their inclination to engage in emotional labor. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  8. Is Br2 hydration hydrophobic?

    Science.gov (United States)

    Alcaraz-Torres, A; Gamboa-Suárez, A; Bernal-Uruchurtu, M I

    2017-02-28

    The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

  9. Localized surface disruptions observed by InSAR during strong earthquakes in Java and Hawai'i

    Science.gov (United States)

    Poland, M.

    2010-01-01

    Interferometric Synthetic Aperture Radar data spanning strong earthquakes on the islands of Java and Hawai‘i in 2006 reveal patches of subsidence and incoherence indicative of localized ground failure. Interferograms spanning the 26 May 2006 Java earthquake suggest an area of about 7.5 km2 of subsidence (~2 cm) and incoherence south of the city of Yogyakarta that correlates with significant damage to housing, high modeled peak ground accelerations, and poorly consolidated geologic deposits. The subsidence and incoherence is inferred to be a result of intense shaking and/or damage. At least five subsidence patches on the west side of the Island of Hawai‘i, ranging 0.3–2.2 km2 in area and 3–8 cm in magnitude, occurred as a result of a pair of strong earthquakes on 15 October 2006. Although no felt reports or seismic data are available from the areas in Hawai‘i, the Java example suggests that the subsidence patches indicate areas of amplified earthquake shaking. Surprisingly, all subsidence areas in Hawai‘i were limited to recent, and supposedly stable, lava flows and may reflect geological conditions not detectable at the surface. In addition, two ‘a‘ā lava flows in Hawai‘i were partially incoherent in interferograms spanning the earthquakes, indicating surface disruption as a result of the earthquake shaking. Coearthquake incoherence of rubbly deposits, like ‘a‘ā flows, should be explored as a potential indicator of earthquake intensity and past strong seismic activity.

  10. Strong Dependence of U.S. Summertime Air Quality on the Decadal Variability of Atlantic Sea Surface Temperatures

    Science.gov (United States)

    Shen, Lu; Mickley, Loretta J.; Leibensperger, Eric M.; Li, Mingwei

    2017-12-01

    We find that summertime air quality in the eastern U.S. displays strong dependence on North Atlantic sea surface temperatures, resulting from large-scale ocean-atmosphere interactions. Using observations, reanalysis data sets, and climate model simulations, we further identify a multidecadal variability in surface air quality driven by the Atlantic Multidecadal Oscillation (AMO). In one-half cycle ( 35 years) of the AMO from cold to warm phase, summertime maximum daily 8 h ozone concentrations increase by 1-4 ppbv and PM2.5 concentrations increase by 0.3-1.0 μg m-3 over much of the east. These air quality changes are related to warmer, drier, and more stagnant weather in the AMO warm phase, together with anomalous circulation patterns at the surface and aloft. If the AMO shifts to the cold phase in future years, it could partly offset the climate penalty on U.S. air quality brought by global warming, an effect which should be considered in long-term air quality planning.

  11. Hydrophobic and hydrophilic control in polyphosphazene materials

    Science.gov (United States)

    Steely, Lee Brent

    This thesis is the culmination of several recent studies focused on the surface characterization of polyphosphazenes specifically the properties of water repellency or hydrophobicity. Chapter 1 is a background account of polyphosphazene chemistry and the hydrophobicity of polyphosphazenes. Chapter 2 provides an examination of the role of surface morphology on hydrophobicity. This study deals in depth with the electrospinning of poly[bis(2,2,2-trifluoroethoxy)phosphazene] in tetrahydrofuran. This process yields fiber mats or bead and fiber mats which exhibit roughness in continuous contact with the water droplet (fiber mats) or discontinuous contact (bead and fiber mats). These surface roughness types are compared to spun cast films using water contact angles to measure the air-water-polymer interface. The influence of aromatic moieties and fluorine content on the air-water-polymer interface is examined in Chapter 3. This study examines the influence of fluorine content and aryloxy groups on the hydrophobicity of a polyphosphazene surface via static water contact angle measurements on a goniometer. Polymer surfaces of spun cast and electrospun mats were probed with advancing, receeding, and static water contact angle and dip coated slides of the same materials were also examined with a Langmuir-Blogett trough. Chapter 4 is a description of the environmental plasma surface treatments of polyphosphazenes as a method of functionalizing solid polymer surfaces. The treatment procedure of functionalizing spun cast and electrospun poly[bis(2,2,2-trifluoroethoxy)phosphazene] surfaces with plasma gases of oxygen, nitrogen, methane, and tetrafluoromethane is detailed. The resulting functionalization of the surface is examined with XPS and water contact angle data. In Chapter 5 fluoroalkoxy polyphosphazenes were processed with liquid carbon dioxide into foams. The foams were then tested for flame retardance and hydrophobicity. Appendixes A-C contain studies on moisture

  12. Hydrophobically modified polyelectrolytes : synthesis, properties and interactions with surfactants

    NARCIS (Netherlands)

    Nieuwkerk, A.C.

    1998-01-01

    Hydrophobically modified polyelectrolytes can form micelle-like aggregates, so-called microdomains, in aqueous solution. The hydrophobic side chains constitute the apolar inner part of these microdomains and the hydrophilic groups on the polyelectrolyte backbone are at the surface of the

  13. Defining the Ail Ligand-Binding Surface: Hydrophobic Residues in Two Extracellular Loops Mediate Cell and Extracellular Matrix Binding To Facilitate Yop Delivery.

    Science.gov (United States)

    Tsang, Tiffany M; Wiese, Jeffrey S; Alhabeil, Jamal A; Usselman, Lisa D; Thomson, Joshua J; Matti, Rafla; Kronshage, Malte; Maricic, Natalie; Williams, Shanedah; Sleiman, Naama H; Felek, Suleyman; Krukonis, Eric S

    2017-04-01

    Yersinia pestis , the causative agent of plague, binds host cells to deliver cytotoxic Yop proteins into the cytoplasm that prevent phagocytosis and generation of proinflammatory cytokines. Ail is an eight-stranded β-barrel outer membrane protein with four extracellular loops that mediates cell binding and resistance to human serum. Following the deletion of each of the four extracellular loops that potentially interact with host cells, the Ail-Δloop 2 and Ail-Δloop 3 mutant proteins had no cell-binding activity while Ail-Δloop 4 maintained cell binding (the Ail-Δloop 1 protein was unstable). Using the codon mutagenesis scheme SWIM (selection without isolation of mutants), we identified individual residues in loops 1, 2, and 3 that contribute to host cell binding. While several residues contributed to the binding of host cells and purified fibronectin and laminin, as well as Yop delivery, three mutations, F80A (loop 2), S128A (loop 3), and F130A (loop 3), produced particularly severe defects in cell binding. Combining these mutations led to an even greater reduction in cell binding and severely impaired Yop delivery with only a slight defect in serum resistance. These findings demonstrate that Y. pestis Ail uses multiple extracellular loops to interact with substrates important for adhesion via polyvalent hydrophobic interactions. Copyright © 2017 American Society for Microbiology.

  14. Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

    2017-10-19

    Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  15. Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

    KAUST Repository

    Huang, Jianfeng

    2015-08-13

    Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H2O2 solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

  16. Size-dependent Young’s modulus in ZnO nanowires with strong surface atomic bonds

    Science.gov (United States)

    Fan, Shiwen; Bi, Sheng; Li, Qikun; Guo, Qinglei; Liu, Junshan; Ouyang, Zhongliang; Jiang, Chengming; Song, Jinhui

    2018-03-01

    The mechanical properties of size-dependent nanowires are important in nano-electro-mechanical systems (NEMSs), and have attracted much research interest. Characterization of the size effect of nanowires in atmosphere directly to broaden their practical application instead of just in high vacuum situations, as reported previously, is desperately needed. In this study, we systematically studied the Young’s modulus of vertical ZnO nanowires in atmosphere. The diameters ranged from 48 nm to 239 nm with a resonance method using non-contact atomic force microscopy. The values of Young’s modulus in atmosphere present extremely strong increasing tendency with decreasing diameter of nanowire due to stronger surface atomic bonds compared with that in vacuum. A core-shell model for nanowires is proposed to explore the Young’s modulus enhancement in atmosphere, which is correlated with atoms of oxygen occurring near the nanowire surface. The modified model is more accurate for analyzing the mechanical behavior of nanowires in atmosphere compared with the model in vacuum. Furthermore, it is possible to use this characterization method to measure the size-related elastic properties of similar wire-sharp nanomaterials in atmosphere and estimate the corresponding mechanical behavior. The study of the size-dependent Young’s modulus in ZnO nanowires in atmosphere will improve the understanding of the mechanical properties of nanomaterials as well as providing guidance for applications in NEMSs, nanogenerators, biosensors and other related areas.

  17. Experimental investigation of effect of surface gravity waves and spray on heat and momentum flux at strong wind conditions

    Science.gov (United States)

    Troitskaya, Yuliya; Sergeev, Daniil; Vdovin, Maxim; Kandaurov, Alexander; Ermakova, Olga; Kazakov, Vassily

    2015-04-01

    The most important characteristics that determine the interaction between atmosphere and ocean are fluxes of momentum, heat and moisture. For their parameterization the dimensionless exchange coefficients (the surface drag coefficient CD and the heat transfer coefficient or the Stanton number CT) are used. Numerous field and laboratory experiments show that CD increases with increasing wind speed at moderate and strong wind, and as it was shows recently CD decreases at hurricane wind speed. Waves are known to increase the sea surface resistance due to enhanced form drag, the sea spray is considered as a possible mechanism of the 'drag reduction' at hurricane conditions. The dependence of heat transfer coefficient CD on the wind speed is not so certain and the role of the mechanism associated with the wave disturbances in the mass transfer is not completely understood. Observations and laboratory data show that this dependence is weaker than for the CD, and there are differences in the character of the dependence in different data sets. The purpose of this paper is investigation of the effect of surface waves on the turbulent exchange of momentum and heat within the laboratory experiment, when wind and wave parameters are maintained and controlled. The effect of spray on turbulent exchange at strong winds is also estimated. A series of experiments to study the processes of turbulent exchange of momentum and heat in a stably stratified temperature turbulent boundary layer air flow over waved water surface were carried out at the Wind - wave stratified flume of IAP RAS, the peculiarity of this experiment was the option to change the surface wave parameters regardless of the speed of the wind flow in the channel. For this purpose a polyethylene net with the variable depth (0.25 mm thick and a cell of 1.6 mm × 1.6mm) has been stretched along the channel. The waves were absent when the net was located at the level of the undisturbed water surface, and had maximum

  18. Bioaccessible Porosity: A new approach to assess residual contamination after bioremediation of hydrophobic organic compounds in sub-surface microporous environments

    Science.gov (United States)

    Akbari, A.; Ghoshal, S.

    2016-12-01

    We define a new parameter, "bioaccessible porosity", the fraction of aggregate volume accessible to soil bacteria, towards a priori assessment of hydrocarbon bioremediation end points. Microbial uptake of poorly soluble hydrocarbons occurs through direct uptake or micellar solubilzation/emulsification associated with biosurfactant production, and requires close proximity of bacteria and hydrocarbon phase. In subsurface microporous environments, bioremediation rates are attenuated when residual hydrophobic contamination is entrapped in sterically restrictive environments which is not accessible to soil bacteria. This study presents new approaches for characterization of the microstructure of porous media and as well, the ability of indigenous hydrocarbon degraders to access to a range of pore sizes. Bacterial access to poorly soluble hydrocarbons in soil micro pores were simulated with bioreactors with membranes with different pore sizes containing the hydrocarbon degrading bacteria, Dietzia maris. D. maris is Gram-positive, and nonmotile that we isolated as the major hydrocarbon degrader from a fine-grained, weathered, hydrocarbon-contaminated site soil. Under nutritional stress, planktonic D. maris cells were aggregated and accessed 5 µm but not 3 µm and smaller pores. However, when hexadecane was available at the pore mouth, D. maris colonized the pore mouth, and accessed pores as small as 0.4 µm. This suggests bacterial accessibility to different pore sizes is regulated by nutritional conditions. A combination of X-ray micro-CT scanning, gas adsorption and mercury intrusion porosimetry was used to characterize the range of pore sizes of soil aggregates. In case of the studied contaminated soil, the bioaccessible porosity were determined as 25% , 27% and 29% (assuming 4, 1, 0.4 µm respectively as accessibility criteria), and about 2.7% of aggregate volume was attributed to 0.006-0.4 µm pores. The 2% aggregate volume at an assumed saturation of 10% could

  19. Liposomes coated with hydrophobically modified hydroxyethyl cellulose: Influence of hydrophobic chain length and degree of modification.

    Science.gov (United States)

    Smistad, Gro; Nyström, Bo; Zhu, Kaizheng; Grønvold, Marthe Karoline; Røv-Johnsen, Anne; Hiorth, Marianne

    2017-08-01

    Nanoparticulate systems with an uncharged hydrophilic surface may have a great potential in mucosal drug delivery. In the present study liposomes were coated with hydrophobically modified hydroxyethyl cellulose (HM-HEC) to create a sterically stabilized liposomal system with an uncharged surface. The aim was to clarify the influence of the amount of hydrophobic modification of HEC and the length of the hydrophobic moiety, on the stability of the system and on the release properties. HM-HEC with different degrees of hydrophobic modification (1 and 2mol%) and hydrophobic groups with different chain lengths (C8, C12, C16) were included in the study, as well as fluid phase and gel phase liposomes. Both types of liposomes were successfully coated with HM-HEC containing 1mol% of hydrophobic groups, while 2mol% did not work for the intended pharmaceutical applications. The polymer coated gel phase liposomes were stable (size, zeta potential, leakage) for 24 weeks at 4°C, with no differences between the C8 and C16 HM-HEC coating. For the fluid phase liposomes a size increase was observed after 24 weeks at 4°C for all formulations; the C8 HM-HEC coated liposomes increased the most. No differences in the leakage during storage at 4°C or in the release at 35°C were observed between the fluid phase formulations. To conclude; HM-HEC with a shorter hydrophobic chain length resulted in a less stable product for the fluid phase liposomes, while no influence of the chain length was observed for the gel phase liposomes (1mol% HM). Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Hydrophobic properties and chemical characterisation of natural water repellent materials in Australian sands

    Science.gov (United States)

    Franco, C. M. M.; Clarke, P. J.; Tate, M. E.; Oades, J. M.

    2000-05-01

    Water-repellency in non-wetting sands is due to hydrophobic waxes present on the surface of sand grains and contained in particulate organic matter present in these sands. This study investigates the physico-chemical characteristics of these natural waxes and compares them to waxes extracted from potential original source materials. Non-polar and polar hydrophobic wax extracts were obtained from whole non-wetting sand, and its individual constituents, and associated organic matter. These included the sand fraction, the intrinsic particulate organic matter, tree litter, eucalyptus leaves, bark, lucerne and lupin plants, and fungi and actinomycetes isolated from these sands. Waxes were characterised for their hydrophobic properties and composition of their chemical constituents. The hydrophobicities of the waxes were assessed by measuring the water-repellency induced after treating acid washed sand with wax extracts. Non-polar and polar wax extracts of the tree litter displayed hydrophobic properties that were similar to the corresponding waxes isolated from non-wetting sand and intrinsic particulate organic matter. Unlike these plant-derived waxes, the microbial wax extracts possessed different hydrophobic properties. Characterisation of the components of the extracted waxes by gas chromatography-mass spectroscopy (GC-MS) analysis revealed a strong similarity in the composition of waxes isolated from non-wetting sand, tree litter and other plant material. The major components found were unbranched and branched C16 to C36 fatty acids and their esters, alkanes, phytanols, phytanes, and sterols. Some of these components were not detected in the microbial waxes. Unextracted samples, as well as wax extracts of non-wetting sand, intrinsic particulate organic matter, tree litter and fresh plant material were further analysed by solution and solid state Nuclear Magnetic Resonance spectroscopy which revealed the relative content of the different chemical species present.

  1. Effects of strong earthquakes in variations of electrical and meteorological parameters of the near-surface atmosphere in Kamchatka region

    Science.gov (United States)

    Smirnov, S. E.; Mikhailova, G. A.; Mikhailov, Yu. M.; Kapustina, O. V.

    2017-09-01

    The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, M = 8.3; January 13, 2007, M = 8.1; January 30, 2016, M = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six-seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

  2. Insights into the Hendra virus NTAIL-XD complex: Evidence for a parallel organization of the helical MoRE at the XD surface stabilized by a combination of hydrophobic and polar interactions.

    Science.gov (United States)

    Erales, Jenny; Beltrandi, Matilde; Roche, Jennifer; Maté, Maria; Longhi, Sonia

    2015-08-01

    The Hendra virus is a member of the Henipavirus genus within the Paramyxoviridae family. The nucleoprotein, which consists of a structured core and of a C-terminal intrinsically disordered domain (N(TAIL)), encapsidates the viral genome within a helical nucleocapsid. N(TAIL) partly protrudes from the surface of the nucleocapsid being thus capable of interacting with the C-terminal X domain (XD) of the viral phosphoprotein. Interaction with XD implies a molecular recognition element (MoRE) that is located within N(TAIL) residues 470-490, and that undergoes α-helical folding. The MoRE has been proposed to be embedded in the hydrophobic groove delimited by helices α2 and α3 of XD, although experimental data could not discriminate between a parallel and an antiparallel orientation of the MoRE. Previous studies also showed that if the binding interface is enriched in hydrophobic residues, charged residues located close to the interface might play a role in complex formation. Here, we targeted for site directed mutagenesis two acidic and two basic residues within XD and N(TAIL). ITC studies showed that electrostatics plays a crucial role in complex formation and pointed a parallel orientation of the MoRE as more likely. Further support for a parallel orientation was afforded by SAXS studies that made use of two chimeric constructs in which XD and the MoRE were covalently linked to each other. Altogether, these studies unveiled the multiparametric nature of the interactions established within this complex and contribute to shed light onto the molecular features of protein interfaces involving intrinsically disordered regions. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Coating with genetic engineered hydrophobin promotes growth of fibroblasts on a hydrophobic solid

    NARCIS (Netherlands)

    Janssen, M.I.; Leeuwen, M.B.M. van; Scholtmeijer, K.; Kooten, T.G. van; Dijkhuizen, L.; Wösten, H.A.B.

    2002-01-01

    Class I Hydrophobins self-assemble at hydrophilic-hydrophobic interfaces into a highly insoluble amphipathic film. Upon self-assembly of these fungal proteins hydrophobic solids turn hydrophilic, while hydrophilic materials can be made hydrophobic. Hydrophobins thus change the nature of a surface.

  4. The new view of hydrophobic free energy.

    Science.gov (United States)

    Baldwin, Robert L

    2013-04-17

    In the new view, hydrophobic free energy is measured by the work of solute transfer of hydrocarbon gases from vapor to aqueous solution. Reasons are given for believing that older values, measured by solute transfer from a reference solvent to water, are not quantitatively correct. The hydrophobic free energy from gas-liquid transfer is the sum of two opposing quantities, the cavity work (unfavorable) and the solute-solvent interaction energy (favorable). Values of the interaction energy have been found by simulation for linear alkanes and are used here to find the cavity work, which scales linearly with molar volume, not accessible surface area. The hydrophobic free energy is the dominant factor driving folding as judged by the heat capacity change for transfer, which agrees with values for solvating hydrocarbon gases. There is an apparent conflict with earlier values of hydrophobic free energy from studies of large-to-small mutations and an explanation is given. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  5. Crystallization Behavior of Phosphate Glasses with Hydrophobic Coating Materials

    Directory of Open Access Journals (Sweden)

    Jaeyeop Chung

    2015-01-01

    Full Text Available We analyzed the effect of the addition of Li2O3, TiO2, and Fe2O3 on the crystallization behavior of P2O5–CaO–SiO2–K2O glasses and the effect of the crystallization behavior on the roughness and hydrophobicity of the coated surface. Exothermic behavior, including a strong exothermic peak in the 833–972 K temperature range when Fe2O3, TiO2, or Li2O3 was added, was confirmed by differential thermal analysis. The modified glass samples (PFTL1–3 showed diffraction peaks when heated at 1073 and 1123 K for 5 min; the crystallized phase corresponds to Fe3(PO42, that is, graftonite. We confirmed that the intensity of the diffraction peaks increases at high temperatures and with increasing Li2O3 content. In the case of the PFTL3 glass, a Li3Fe2(PO42 phase, that is, trilithium diiron(III tris[phosphate(V], was observed. Through scanning electron microscopy and the contact angles of the surfaces with water, we confirmed that the increase in surface roughness, correlated to the crystallization of the glass frit, increases hydrophobicity of the surface. The calculated values of the local activation energies for the growth of Fe3(PO42 on the PTFL1, PTFL2, and PFTL3 glass were 237–292 kJ mol−1, 182–258 kJ mol−1, and 180–235 kJ mol−1.

  6. Super-hydrophobicity fundamentals: implications to biofouling prevention.

    Science.gov (United States)

    Marmur, Abraham

    2006-01-01

    The theory of wetting on super-hydrophobic surfaces is presented and discussed, within the general framework of equilibrium wetting and contact angles. Emphasis is put on the implications of super-hydrophobicity to the prevention of biofouling. Two main lines of thought are discussed, viz. i) "mirror imaging" of the Lotus effect, namely designing a surface that repels biological entities by being super-hydrophilic, and ii) designing a surface that minimises the water-wetted area when submerged in water (by keeping an air film between the water and the surface), so that the suspended biological entities have a low probability of encountering the solid surface.

  7. Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

    Directory of Open Access Journals (Sweden)

    Gudrun Petzold

    2011-08-01

    Full Text Available Polyelectrolyte complexes (PECs were prepared by structural uniform and strongly charged cationic and anionic modified alternating maleic anhydride copolymers. The hydrophobicity of the polyelectrolytes was changed by the comonomers (ethylene, isobutylene and styrene. Additionally, the n−/n+ ratio of the molar charges of the polyelectrolytes and the procedure of formation were varied. The colloidal stability of the systems and the size, shape, and structure of the PEC particles were investigated by turbidimetry, dynamic light scattering (DLS and atomic force microscopy (AFM. Dynamic light scattering indicates that beside large PEC particle aggregates distinct smaller particles were formed by the copolymers which have the highest hydrophobicity (styrene. These findings could be proved by AFM. Fractal dimension (D, root mean square (RMS roughness and the surface profiles of the PEC particles adsorbed on mica allow the following conclusions: the higher the hydrophobicity of the polyelectrolytes, the broader is the particle size distribution and the minor is the swelling of the PEC particles. Hence, the most compact particles are formed with the very hydrophobic copolymer.

  8. Adsorption of hydrophobically end-capped poly(ethylene glycol) on cellulose.

    Science.gov (United States)

    Holappa, Susanna; Kontturi, Katri S; Salminen, Arto; Seppälä, Jukka; Laine, Janne

    2013-11-12

    Adsorption of poly(ethylene glycol), hydrophobically end-capped with octadecenylsuccinic anhydride (OSA-PEG-OSA), on an ultrathin film of cellulose has been studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). Normally, PEG does not adsorb on cellulosic surfaces, but the use of the telechelic hydrophobic modification was found to promote adsorption. The influence of the conformation of the polymer in solution prior to adsorption and the subsequent properties of the adsorbed layer were investigated. The adsorption experiments were done at concentrations below and above the critical association concentration. The adsorption of OSA-PEG-OSA on cellulose was observed to occur in four distinct stages. Because of the amphiphilic nature of cellulose, further adsorption experiments were performed on hydrophobic (polystyrene) and hydrophilic (silica) model substrates to illuminate the contribution of hydrophobic and hydrophilic factors in the adsorption phenomenon. As expected, the kinetics and the mechanism of adsorption were strongly dependent on the chemical composition of the substrate.

  9. Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    York, Roger L. [Univ. of California, Berkeley, CA (United States)

    2007-01-01

    Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model peptides and amino acids, surface specific SFG vibrational spectroscopy can be a powerful tool to elucidate the interfacial structure of these adsorbates. Herein, four experiments are described. In one, a series of isosequential amphiphilic peptides are synthesized and studied when adsorbed to both hydrophobic and hydrophilic surfaces. On hydrophobic surfaces of deuterated polystyrene, it was determined that the hydrophobic part of the peptide is ordered at the solid-liquid interface, while the hydrophilic part of the peptide appears to have a random orientation at this interface. On a hydrophilic surface of silica, it was determined that an ordered peptide was only observed if a peptide had stable secondary structure in solution. In another experiment, the interfacial structure of a model amphiphilic peptide was studied as a function of the ionic strength of the solution, a parameter that could change the peptide's secondary structure in solution. It was determined that on a hydrophobic surface, the peptide's interfacial structure was independent of its structure in solution. This was in contrast to the adsorbed structure on a hydrophilic surface, where the peptide's interfacial structure showed a strong dependence on its solution secondary structure. In a third experiment, the SFG spectra of lysine and proline amino acids on both hydrophobic and hydrophilic surfaces were obtained by using a different experimental geometry that increases the SFG signal

  10. Evaporation of Nanosuspensions on Substrates with Different Hydrophobicity.

    Science.gov (United States)

    Perrin, Lionel; Pajor-Swierzy, Anna; Magdassi, Shlomo; Kamyshny, Alexander; Ortega, Francisco; Rubio, Ramón G

    2018-01-24

    Liquid drop evaporation on surfaces is present in many industrial and medical applications, e.g., printed electronics, spraying of pesticides, DNA mapping, etc. Despite this strong interest, a theoretical description of the dynamic of the evaporation of complex liquid mixtures and nanosuspensions is still lacking. Indeed, one of the aspects that have not been included in the current theoretical descriptions is the competition between the kinetics of evaporation and the adsorption of surfactants and/or particles at the liquid/vapor and liquid/solid interfaces. Materials formed by an electrically isolating solid on which a patterned conducting layer was formed by the deposits left after drop evaporation have been considered as very promising for building electrical circuits on flexible plastic substrates. In this work, we have done an exhaustive study of the evaporation of nanosuspensions of latex and hydrophobized silver nanoparticles on four substrates of different hydrophobicity. The advancing and receding contact angles as well as the time dependence of the volume of the droplets have been measured over a broad range of particle concentrations. Also, mixtures of silver particles and a surfactant, commonly used in industrial printing, have been examined. Furthermore, the adsorption kinetics at both the air/liquid and solid/liquid interfaces have been measured. Whereas the latex particles do not adsorb at the solid/liquid and only slightly reduce the surface tension, the silver particles strongly adsorb at both interfaces. The experimental results of the evaporation process were compared with the predictions of the theory of Semenov et al. (Evaporation of Sessile Water Droplets: Universal Behavior in the Presence of Contact Angle Hysteresis. Colloids Surf. Physicochem. Eng. Asp. 2011, 391 (1-3), 135-144) and showed surprisingly good agreement despite that the theory was developed for pure liquids. The morphology of the deposits left by the droplets after total

  11. Influence of elastomeric seal plate surface chemistry on interface integrity in biofouling-prone systems: Evaluation of a hydrophobic "easy-release" silicone-epoxy coating for maintaining water seal integrity of a sliding neoprene/steel interface

    Science.gov (United States)

    Andolina, Vincent L.

    The scientific hypothesis of this work is that modulation of the properties of hard materials to exhibit abrasion-reducing and low-energy surfaces will extend the functional lifetimes of elastomeric seals pressed against them in abrasive underwater systems. The initial motivation of this work was to correct a problem noted in the leaking of seals at major hydropower generating facilities subject to fouling by abrasive zebra mussel shells and extensive corrosion. Similar biofouling-influenced problems can develop at seals in medical devices and appliances from regulators in anesthetic machines and SCUBA diving oxygen supply units to autoclave door seals, injection syringe gaskets, medical pumps, drug delivery components, and feeding devices, as well as in food handling equipment like pasteurizers and transfer lines. Maritime and many other heavy industrial seal interfaces could also benefit from this coating system. Little prior work has been done to elucidate the relationship of seal plate surface properties to the friction and wear of elastomeric seals during sliding contacts of these articulating materials, or to examine the secondary influence of mineralized debris within the contacting interfaces. This investigation utilized the seal materials relevant to the hydropower application---neoprene elastomer against carbon steel---with and without the application of a silicone-epoxy coating (WearlonRTM 2020.98) selected for its wear-resistance, hydrophobicity, and "easy-release" capabilities against biological fouling debris present in actual field use. Analytical techniques applied to these materials before and after wear-producing processes included comprehensive Contact Angle measurements for Critical Surface Tension (CA-CST) determination, Scanning Electron Microscopic inspections, together with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-Ray Fluorescence (XRF) measurements for determination of surface texture and inorganic composition, Multiple

  12. Phenomenological Model of Hydrophobic and Hydrophilic Interactions

    Science.gov (United States)

    Menshikov, L. I.; Menshikov, P. L.; Fedichev, P. O.

    2017-12-01

    Hydration forces acting between macroscopic bodies at distances L ≤ 3 nm in pure water are calculated based on the phenomenological model of polar liquids. It is shown that depending on the properties of the bodies, the interacting surfaces polarize the liquid differently, and wetting properties of the surfaces are completely characterized by two parameters. If the surfaces are hydrophilic, liquid molecules are polarized at right angles to the surfaces, and the interaction is the short-range repulsion (the forces of interaction decrease exponentially over the characteristic length λ ≈ 0.2 nm). The interaction between the hydrophobic surfaces is more diversified and has been studied less. For L ≤ 3 nm, the interaction exhibits universal properties, while for L ≤ 3 nm, it considerably depends on the properties of the surfaces and on the distances between them, as well as on the composition of the polar liquid. In full agreement with the available experimental results we find that if the interfaces are mostly hydrophobic, then the interaction is attractive and long-range (the interaction forces diminish exponentially with decay length 1.2 nm). In this case, the resultant polarization of water molecules is parallel to the surface. It is shown that hydration forces are determined by nonlinear effects of polarization of the liquid in the bulk or by analogous nonlinearity of the interaction of water with a submerged body. This means that the forces of interaction cannot be calculated correctly in the linear response approximation. The forces acting between hydrophobic or hydrophilic surfaces are of the entropy type or electrostatic, respectively. It is shown that hydrophobic and hydrophilic surfaces for L ≤ 3 nm repel each other. The calculated intensity of their interaction is in agreement with experimental data. We predict the existence of an intermediate regime in which a body cannot order liquid molecules, which results in a much weaker attraction that

  13. Gas solubility in hydrophobic confinement.

    Science.gov (United States)

    Luzar, Alenka; Bratko, Dusan

    2005-12-01

    Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the

  14. Solution properties of hydrophobically modified

    Directory of Open Access Journals (Sweden)

    A.M. Al-Sabagh

    2016-12-01

    Full Text Available We tested nine hydrophobically modified polyacrylamides with molecular weights situated between 1.58 and 0.89 × 106 g/mol for enhanced oil recovery applications. Their solution properties were investigated in the distilled water, brine solution, formation water and sea water. Their critical association concentrations were determined from the relationship between their concentrations and the corresponding apparent viscosities (ηapp at 30 °C at shear rate 6 s−1. They were between 0.4 and 0.5 g/dl. The brine solutions of 0.5 g/dl of HM-PAMs were investigated at different conditions regarding their apparent viscosities. Such conditions were mono and divalent cations, temperature ranging from 30 to 90 °C, the shear rate ranging from 6 to 30 s−1 and the aging time for 45 days. The surface and interfacial tensions for the HM-PAMs were measured for concentration range from 0.01 to 1 g/dl brine solutions at 30 °C and their emulsification efficiencies were investigated for 7 days. The discrepancy in the properties and efficiencies of the tested copolymers was discussed in the light of their chemical structure.

  15. A novel method to fabricate water-soluble hydrophobic agent and super-hydrophobic film on pretreated metals

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Liqun [School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Xueyuan Road 37, Haidian District, Beijing 100083 (China)]. E-mail: zhulq@buaa.edu.cn; Jin Yan [School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Xueyuan Road 37, Haidian District, Beijing 100083 (China)]. E-mail: jinyan2080@hotmail.com

    2007-01-30

    This paper demonstrated a convenient method to prepare water-soluble hydrophobic agent and create super-hydrophobic film on the basic material of phosphating film and electroless Ni-P composite coating on carbon steels. Water contact angles and rolling angles of super-hydrophobic films were 155-168{sup o} and 2-3{sup o} on phosphating films, respectively, 145-155 deg. and 15-20 deg. on electroless Ni-P composite coatings, respectively. This water-soluble hydrophobic agent was white latex and had lots of micro-particles suspending in it. The thickness of the single-layer super-hydrophobic film with good corrosion resistance and stability was about 2-3 {mu}m. The microstructure of super-hydrophobic film was discussed using XRD, EDS, optical and electronic microscope as analytical methods. This kind of super-hydrophobic film had a great many micro-particles dispersing in the surface, which contained F and Si and greatly increased the roughness of the surface.

  16. Enhancing the hydrophobic effect in confined water nanodrops.

    Science.gov (United States)

    Rao, Palla Venkata Gopala; Gandhi, K S; Ayappa, K G

    2007-12-18

    The distribution of hydrophobic solutes, such as methane, enclosed in a nanosized water droplet contained in a reverse micelle of diameter 2.82 nm is investigated using Monte Carlo simulations. The effect of the hydrophobic solute's atomic diameter on the solute-solute potential of mean force is also studied. The study reveals that confinement has a strong influence on the solute's tendency to associate. The potential of mean force exhibits only a single minimum, indicating that the contact pair is the only stable configuration between solutes. The solvent-separated pair that is universally observed for small solutes in bulk water is conspicuously absent. This enhanced hydrophobic effect is attributed to the lack of sufficient water to completely hydrate and stabilize the solvent-separated configurations. The study is expected to be important in understanding the role of hydrophobic forces during protein folding and nucleation under confinement.

  17. Dynamically slow processes in supercooled water confined between hydrophobic plates

    Energy Technology Data Exchange (ETDEWEB)

    Franzese, Giancarlo [Departamento de Fisica Fundamental, Universidad de Barcelona, Diagonal 647, Barcelona 08028 (Spain); Santos, Francisco de los, E-mail: gfranzese@ub.ed, E-mail: fdlsant@ugr.e [Departamento de Electromagnetismo y Fisica de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2009-12-16

    We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

  18. Identification and characterization of hydrophobic gate residues in TRP channels.

    Science.gov (United States)

    Zheng, Wang; Hu, Ruikun; Cai, Ruiqi; Hofmann, Laura; Hu, Qiaolin; Fatehi, Mohammad; Long, Wentong; Kong, Tim; Tang, Jingfeng; Light, Peter; Flockerzi, Veit; Cao, Ying; Chen, Xing-Zhen

    2018-02-01

    Transient receptor potential (TRP) channels, subdivided into 6 subfamilies in mammals, have essential roles in sensory physiology. They respond to remarkably diverse stimuli, comprising thermal, chemical, and mechanical modalities, through opening or closing of channel gates. In this study, we systematically substituted the hydrophobic residues within the distal fragment of pore-lining helix S6 with hydrophilic residues and, based on Xenopus oocyte and mammalian cell electrophysiology and a hydrophobic gate theory, identified hydrophobic gates in TRPV6/V5/V4/C4/M8. We found that channel activity drastically increased when TRPV6 Ala616 or Met617 or TRPV5 Ala576 or Met577 , but not any of their adjacent residues, was substituted with hydrophilic residues. Channel activity strongly correlated with the hydrophilicity of the residues at those sites, suggesting that consecutive hydrophobic residues TRPV6 Ala616-Met617 and TRPV5 Ala576-Met577 form a double-residue gate in each channel. By the same strategy, we identified a hydrophobic single-residue gate in TRPV4 Iso715 , TRPC4 Iso617 , and TRPM8 Val976 . In support of the hydrophobic gate theory, hydrophilic substitution at the gate site, which removes the hydrophobic gate seal, substantially increased the activity of TRP channels in low-activity states but had little effect on the function of activated channels. The double-residue gate channels were more sensitive to small changes in the gate's hydrophobicity or size than single-residue gate channels. The unconventional double-reside gating mechanism in TRP channels may have been evolved to respond especially to physiologic stimuli that trigger relatively small gate conformational changes.-Zheng, W., Hu, R., Cai, R., Hofmann, L., Hu, Q., Fatehi, M., Long, W., Kong, T., Tang, J., Light, P., Flockerzi, V., Cao, Y., Chen, X.-Z. Identification and characterization of hydrophobic gate residues in TRP channels.

  19. Influence of Hydrophobicity on Polyelectrolyte Complexation

    Energy Technology Data Exchange (ETDEWEB)

    Sadman, Kazi [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Wang, Qifeng [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Chen, Yaoyao [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Keshavarz, Bavand [Department; Jiang, Zhang [X-ray; Shull, Kenneth R. [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States

    2017-11-16

    Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) with methyl, ethyl and propyl substituents– thereby increasing the hydrophobicity with increasing side chain length– and complexing them with a common anionic polyelectrolyte, poly(styrene sulfonate). The mechanical 1 ACS Paragon Plus Environment behavior of these complexes is compared to the more hydrophilic system of poly(styrene sulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling-modulus master curves that are quantified in this work. The rheological behavior of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.

  20. Different assembly of type IV collagen on hydrophilic and hydrophobic substrata alters endothelial cells interaction

    Directory of Open Access Journals (Sweden)

    NM Coelho

    2010-06-01

    Full Text Available Considering the structural role of type IV collagen (Col IV in the assembly of the basement membrane (BM and the perspective of mimicking its organization for vascular tissue engineering purposes, we studied the adsorption pattern of this protein on model hydrophilic (clean glass and hydrophobic trichloro(octadecylsilane (ODS surfaces known to strongly affect the behavior of other matrix proteins. The amount of fluorescently labeled Col IV was quantified showing saturation of the surface for concentration of the adsorbing solution of about 50μg/ml, but with approximately twice more adsorbed protein on ODS. AFM studies revealed a fine – nearly single molecular size – network arrangement of Col IV on hydrophilic glass, which turns into a prominent and growing polygonal network consisting of molecular aggregates on hydrophobic ODS. The protein layer forms within minutes in a concentration-dependent manner. We further found that human umbilical vein endothelial cells (HUVEC attach less efficiently to the aggregated Col IV (on ODS, as judged by the significantly altered cell spreading, focal adhesions formation and the development of actin cytoskeleton. Conversely, the immunofluorescence studies for integrins revealed that the fine Col IV network formed on hydrophilic substrata is better recognized by the cells via both α1 and α2 heterodimers which support cellular interaction, apart from these on hydrophobic ODS where almost no clustering of integrins was observed.

  1. Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates.

    Science.gov (United States)

    He, Yulian; Fishman, Zachary S; Yang, Ke R; Ortiz, Brandon; Liu, Chaolun; Goldsamt, Julia; Batista, Victor S; Pfefferle, Lisa D

    2018-02-07

    A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with p-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (p-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250-350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and 1 H NMR spectroscopy. The resulting hydrophobicity correlates with H 2 temperature-programmed reduction (H 2 -TPR) stability, which therefore provides a practical gauge of hydrophobicity.

  2. Plasmodium falciparum parasites expressing pregnancy-specific variant surface antigens adhere strongly to the choriocarcinoma cell line BeWo

    DEFF Research Database (Denmark)

    Haase, Rikke N; Megnekou, Rosette; Lundquist, Maja

    2006-01-01

    Placenta-sequestering Plasmodium falciparum parasites causing pregnancy-associated malaria express pregnancy-specific variant surface antigens (VSA(PAM)). We report here that VSA(PAM)-expressing patient isolates adhere strongly to the choriocarcinoma cell line BeWo and that the BeWo line can...... be used to efficiently select for VSA(PAM) expression in vitro....

  3. Bacterial surface appendages strongly impact nanomechanical and electrokinetic properties of Escherichia coli cells subjected to osmotic stress.

    Directory of Open Access Journals (Sweden)

    Grégory Francius

    Full Text Available The physicochemical properties and dynamics of bacterial envelope, play a major role in bacterial activity. In this study, the morphological, nanomechanical and electrohydrodynamic properties of Escherichia coli K-12 mutant cells were thoroughly investigated as a function of bulk medium ionic strength using atomic force microscopy (AFM and electrokinetics (electrophoresis. Bacteria were differing according to genetic alterations controlling the production of different surface appendages (short and rigid Ag43 adhesins, longer and more flexible type 1 fimbriae and F pilus. From the analysis of the spatially resolved force curves, it is shown that cells elasticity and turgor pressure are not only depending on bulk salt concentration but also on the presence/absence and nature of surface appendage. In 1 mM KNO(3, cells without appendages or cells surrounded by Ag43 exhibit large Young moduli and turgor pressures (∼700-900 kPa and ∼100-300 kPa respectively. Under similar ionic strength condition, a dramatic ∼50% to ∼70% decrease of these nanomechanical parameters was evidenced for cells with appendages. Qualitatively, such dependence of nanomechanical behavior on surface organization remains when increasing medium salt content to 100 mM, even though, quantitatively, differences are marked to a much smaller extent. Additionally, for a given surface appendage, the magnitude of the nanomechanical parameters decreases significantly when increasing bulk salt concentration. This effect is ascribed to a bacterial exoosmotic water loss resulting in a combined contraction of bacterial cytoplasm together with an electrostatically-driven shrinkage of the surface appendages. The former process is demonstrated upon AFM analysis, while the latter, inaccessible upon AFM imaging, is inferred from electrophoretic data interpreted according to advanced soft particle electrokinetic theory. Altogether, AFM and electrokinetic results clearly demonstrate the

  4. Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography.

    Science.gov (United States)

    Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo

    2015-08-01

    Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Surface-termination-dependent magnetism and strong perpendicular magnetocrystalline anisotropy of an FeRh(001) thin film

    Czech Academy of Sciences Publication Activity Database

    Jekal, S.; Rhim, S.H.; Hong, S.C.; Son, W.-J.; Shick, Alexander

    2015-01-01

    Roč. 92, č. 6 (2015), " 064410-1"-" 064410-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-07172S Institutional support: RVO:68378271 Keywords : magnetic anisotropy * magnetic recording * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  6. Changes in germ tube formation and cell-surface hydrophobicity of oral Candida dubliniensis isolates following brief exposure to sub-cidal concentrations of polyene and azole antifungal agents.

    Science.gov (United States)

    Ellepola, Arjuna N B; Joseph, Bobby K; Khan, Z U

    2013-07-01

    Adherence of Candida has been implicated as the initial process in the pathogenesis of oral candidosis. Candidal germ tubes and its relative cell-surface hydrophobicity (CSH) are contributory attributes. Candida dubliniensis is currently documented as an opportunistic pathogen allied with recurrent oral candidosis. Oral candidosis can be treated with polyene and azole antifungals such as amphotericin B, ketoconazole and fluconazole. However, the intraoral concentration of these drugs fluctuates and becomes sub-therapeutic because of the diluent effect of saliva and cleansing effect of the oral musculature. Hence, intraorally, the pathogenic yeast may undergo a brief exposure to antifungal drugs. The objective of this study was to investigate the effect of brief exposure to sub-lethal concentrations of these antifungals on the germ tube formation and CSH of C. dubliniensis. After determining the minimum inhibitory concentration of the drugs, 20 oral isolates of C. dubliniensis were exposed to sub-lethal concentrations of these antifungals for 1 h. Following this brief exposure, the drugs were removed, and following subsequent incubation in a germ tube inducing medium and exposure to bi-phasic hydrocarbon assay, the germ tube formation and CSH of these isolates was quantified respectively. Compared with controls, exposure to amphotericin B almost completely suppressed the ability to form germ tubes with a mean percentage reduction of 95.91% (P formation but to a lesser degree with a mean percentage reduction of 18.73% and 12.01% respectively (P  0.05). In clinical terms it appears that, even a short exposure to sub-lethal concentrations of these drugs, a situation all too familiar in the oral environment, would continue to exert an antifungal effect by suppressing the pathogenic potency of C. dubliniensis. © 2013 Blackwell Verlag GmbH.

  7. Magnet-induced temporary superhydrophobic coatings from one-pot synthesized hydrophobic magnetic nanoparticles.

    Science.gov (United States)

    Fang, Jian; Wang, Hongxia; Xue, Yuhua; Wang, Xungai; Lin, Tong

    2010-05-01

    In this paper, we report on the production of superhydrophobic coatings on various substrates (e.g., glass slide, silicon wafer, aluminum foil, plastic film, nanofiber mat, textile fabrics) using hydrophobic magnetic nanoparticles and a magnet-assembly technique. Fe(3)O(4) magnetic nanoparticles functionalized with a thin layer of fluoroalkyl silica on the surface were synthesized by one-step coprecipitation of Fe(2+)/Fe(3+) under an alkaline condition in the presence of a fluorinated alkyl silane. Under a magnetic field, the magnetic nanoparticles can be easily deposited on any solid substrate to form a thin superhydrophobic coating with water contact angle as high as 172 degrees , and the surface superhydrophobicity showed very little dependence on the substrate type. The particulate coating showed reasonable durability because of strong aggregation effect of nanoparticles, but the coating layer can be removed (e.g., by ultrasonication) to restore the original surface feature of the substrates. By comparison, the thin particle layer deposited under no magnetic field showed much lower hydrophobicity. The main reason for magnet-induced superhydrophobic surfaces is the formation of nano- and microstructured surface features. Such a magnet-induced temporary superhydrophobic coating may have wide applications in electronic, biomedical, and defense-related areas.

  8. "Life-like" assessment of antimicrobial surfaces by a new touch transfer assay displays strong superiority of a copper alloy compared to silver containing surfaces.

    Directory of Open Access Journals (Sweden)

    Johannes Karl-Mark Knobloch

    Full Text Available Transmission of bacteria from inanimate surfaces in healthcare associated environments is an important source of hospital acquired infections. A number of commercially available medical devices promise to fulfill antibacterial activity to reduce environmental contamination. In this study we developed a touch transfer assay modeling fingerprint transmission to investigate the antibacterial activity of surfaces, with confirmed antibacterial activity by a modified ISO 22196 (JIS Z 2801 assay to test such surfaces under more realistic conditions. Bacteria were taken up from a dry standardized primary contaminated surface (PCS with disinfected fingers or fingers covered with sterile and moistened cotton gloves. Subsequently, bacteria were transferred by pressing on secondary contaminated surfaces (SCS with or without potential antibacterial activity and the relative reduction rate was determined after 24 h. A stable transmission rate between PCS and SCS was observed using moistened sterile gloves. A copper containing alloy displayed at least a tenfold reduction of the bacterial load consistently reaching less than 2.5 cfu/cm2. In contrast, no significant reduction of bacterial contamination by silver containing surfaces and matured pure silver was observed in the touch transfer assay. With the touch transfer assay we successfully established a new reproducible method modeling cross contamination. Using the new method we were able to demonstrate that several surfaces with confirmed antimicrobial activity in a modified ISO 22196 (JIS Z 2801 assay lacked effectiveness under defined ambient conditions. This data indicate that liquid based assays like the ISO 22196 should be critically reviewed before claiming antibacterial activity for surfaces in the setting of contamination of dry surfaces by contact to the human skin. We suggest the newly developed touch transfer assay as a new additional tool for the assessment of potential antimicrobial surfaces

  9. Fluoroalkyl and Alkyl Chains Have Similar Hydrophobicities in Binding to the “Hydrophobic Wall” of Carbonic Anhydrase

    Energy Technology Data Exchange (ETDEWEB)

    J Mecinovic; P Snyder; K Mirica; S Bai; E Mack; R Kwant; D Moustakas; A Heroux; G Whitesides

    2011-12-31

    The hydrophobic effect, the free-energetically favorable association of nonpolar solutes in water, makes a dominant contribution to binding of many systems of ligands and proteins. The objective of this study was to examine the hydrophobic effect in biomolecular recognition using two chemically different but structurally similar hydrophobic groups, aliphatic hydrocarbons and aliphatic fluorocarbons, and to determine whether the hydrophobicity of the two groups could be distinguished by thermodynamic and biostructural analysis. This paper uses isothermal titration calorimetry (ITC) to examine the thermodynamics of binding of benzenesulfonamides substituted in the para position with alkyl and fluoroalkyl chains (H{sub 2}NSO{sub 2}C{sub 6}H{sub 4}-CONHCH{sub 2}(CX{sub 2}){sub n}CX{sub 3}, n = 0-4, X = H, F) to human carbonic anhydrase II (HCA II). Both alkyl and fluoroalkyl substituents contribute favorably to the enthalpy and the entropy of binding; these contributions increase as the length of chain of the hydrophobic substituent increases. Crystallography of the protein-ligand complexes indicates that the benzenesulfonamide groups of all ligands examined bind with similar geometry, that the tail groups associate with the hydrophobic wall of HCA II (which is made up of the side chains of residues Phe131, Val135, Pro202, and Leu204), and that the structure of the protein is indistinguishable for all but one of the complexes (the longest member of the fluoroalkyl series). Analysis of the thermodynamics of binding as a function of structure is compatible with the hypothesis that hydrophobic binding of both alkyl and fluoroalkyl chains to hydrophobic surface of carbonic anhydrase is due primarily to the release of nonoptimally hydrogen-bonded water molecules that hydrate the binding cavity (including the hydrophobic wall) of HCA II and to the release of water molecules that surround the hydrophobic chain of the ligands. This study defines the balance of enthalpic and

  10. Strong linkages between surface and deep-water dissolved organic matter in the East/Japan Sea

    Science.gov (United States)

    Kim, Tae-Hoon; Kim, Guebuem; Shen, Yuan; Benner, Ronald

    2017-05-01

    Vertical and horizontal distributions of total dissolved amino acids (TDAAs), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) were measured in the East/Japan Sea (EJS). The euphotic zone of this sea is N-limited, and the N : P ratio is ˜ 13 below 200 m depth. Elevated TDAA concentrations (137 ± 34 nM) and DOC-normalized yields (0.8 ± 0.2 % of DOC) were observed in deep waters ( ≥ 1000 m) of the EJS and compared with those in the deep North Pacific Ocean. Significantly high TDAA concentrations and yields were observed in a region of deep-water formation, indicating the convection of margin-derived bioavailable dissolved organic matter (DOM) to deep waters. Declining TDAA concentrations (36 ± 12 %) and yields (33 ± 13 %) were observed between 1000 and 3000 m throughout the EJS, indicating the utilization of bioavailable DOM in deep waters. Concentrations of the D-enantiomers of amino acids (Ala, Glx, Asx, and Ser) were relatively high in deep waters of the EJS, indicating substantial bacterial contributions to DOM from surface and upper mesopelagic waters. Climate warming during the past few decades in the EJS is weakening deep convection during the winter, and one consequence of this reduction in deep convection is a decline in the supply of bioavailable DOM from surface waters.

  11. Strong excitation of surface and bulk spin waves in yttrium iron garnet placed in a split ring resonator

    Science.gov (United States)

    Tay, Z. J.; Soh, W. T.; Ong, C. K.

    2018-02-01

    This paper presents an experimental study of the inverse spin Hall effect (ISHE) in a bilayer consisting of a yttrium iron garnet (YIG) and platinum (Pt) loaded on a metamaterial split ring resonator (SRR). The system is excited by a microstrip feed line which generates both surface and bulk spin waves in the YIG. The spin waves subsequently undergo spin pumping from the YIG film to an adjacent Pt layer, and is converted into a charge current via the ISHE. It is found that the presence of the SRR causes a significant enhancement of the mangetic field near the resonance frequency of the SRR, resulting in a significant increase in the ISHE signal. Furthermore, the type of spin wave generated in the system can be controlled by changing the external applied magnetic field angle (θH ). When the external applied magnetic field is near parallel to the microstrip line (θH = 0 ), magnetostatic surface spin waves are predominantly excited. On the other hand, when the external applied magnetic field is perpendicular to the microstrip line (θH = π/2 ), backward volume magnetostatic spin waves are predominantly excited. Hence, it can be seen that the SRR structure is a promising method of achieving spin-charge conversion, which has many advantages over a coaxial probe.

  12. Biofilm, adherence, and hydrophobicity as virulence factors in Malassezia furfur.

    Science.gov (United States)

    Angiolella, Letizia; Leone, Claudia; Rojas, Florencia; Mussin, Javier; de Los Angeles Sosa, María; Giusiano, Gustavo

    2018-01-01

    Malassezia species are natural inhabitants of the healthy skin. However, under certain conditions, they may cause or exacerbate several skin diseases. The ability of this fungus to colonize or infect is determined by complex interactions between the fungal cell and its virulence factors. This study aims to evaluate "in vitro" the hydrophobicity levels, the adherence on a plastic surface and the biofilm formation of 16 clinical isolates of Malassezia furfur. Cellular surface hydrophobicity (CSH) levels were determined by two-phase system. The biofilm formation was determined by tetrazolium salt (XTT) reduction assay and by Scanning Electron Microscopy (SEM). Results showed many isolates were hydrophobic, adherent, and producers of biofilm on abiotic surfaces with different capacity. SEM observations confirmed an abundant extracellular matrix after 48 h of biofilm formation. About 63% of strains with high production of biofilm showed medium to high percentage of hydrophobicity and/or adherence. In addition, it has been demonstrated a correlation between hydrophobicity, adherence, and biofilm formation in about 60% of strains examined. These important virulence factors could be responsible of this yeast changing from a commensal to a pathogenic status. © The Author 2017. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  13. Characterizing an Integrated Annual Global Measure of the Earth's Maximum Land Surface Temperatures from 2003 to 2012 Reveals Strong Biogeographic Influences

    Science.gov (United States)

    Mildrexler, D. J.; Zhao, M.; Running, S. W.

    2014-12-01

    Land Surface Temperature (LST) is a good indicator of the surface energy balance because it is determined by interactions and energy fluxes between the atmosphere and the ground. The variability of land surface properties and vegetation densities across the Earth's surface changes these interactions and gives LST a unique biogeographic influence. Natural and human-induced disturbances modify the surface characteristics and alter the expression of LST. This results in a heterogeneous and dynamic thermal environment. Measurements that merge these factors into a single global metric, while maintaining the important biophysical and biogeographical factors of the land surface's thermal environment are needed to better understand integrated temperature changes in the Earth system. Using satellite-based LST we have developed a new global metric that focuses on one critical component of LST that occurs when the relationship between vegetation density and surface temperature is strongly coupled: annual maximum LST (LSTmax). A 10 year evaluation of LSTmax histograms that include every 1-km pixel across the Earth's surface reveals that this integrative measurement is strongly influenced by the biogeographic patterns of the Earth's ecosystems, providing a unique comparative view of the planet every year that can be likened to the Earth's thermal maximum fingerprint. The biogeographical component is controlled by the frequency and distribution of vegetation types across the Earth's land surface and displays a trimodal distribution. The three modes are driven by ice covered polar regions, forests, and hot desert/shrubland environments. In ice covered areas the histograms show that the heat of fusion results in a convergence of surface temperatures around the melting point. The histograms also show low interannual variability reflecting two important global land surface dynamics; 1) only a small fraction of the Earth's surface is disturbed in any given year, and 2) when

  14. Observation of topological surface states and strong electron/hole imbalance in extreme magnetoresistance compound LaBi

    Science.gov (United States)

    Jiang, J.; Schröter, N. B. M.; Wu, S.-C.; Kumar, N.; Shekhar, C.; Peng, H.; Xu, X.; Chen, C.; Yang, H. F.; Hwang, C.-C.; Mo, S.-K.; Felser, C.; Yan, B. H.; Liu, Z. K.; Yang, L. X.; Chen, Y. L.

    2018-02-01

    The recent discovery of the extreme magnetoresistance (XMR) in the nonmagnetic rare-earth monopnictides La X (X = P, As, Sb, Bi,), a recently proposed new topological semimetal family, has inspired intensive research effort in the exploration of the correlation between the XMR and their electronic structures. In this work, using angle-resolved photoemission spectroscopy to investigate the three-dimensional band structure of LaBi, we unraveled its topologically nontrivial nature with the observation of multiple topological surface Dirac fermions, as supported by our ab initio calculations. Furthermore, we observed substantial imbalance between the volume of electron and hole pockets, which rules out the electron-hole compensation as the primary cause of the XMR in LaBi.

  15. Ultrahydrophobic surface modification of polymeric fibers and inorganic substrates

    Science.gov (United States)

    Ramaratnam, Karthik

    The wettability of a solid surface is a very important property, and is governed by both the chemical composition and the geometrical microstructure of the surface. Wettability and repellency are important properties of solid surfaces from both fundamental and practical aspects. The wettability of the solid surface is a characteristic property of materials and strongly depends on both the surface energy and the surface roughness. These properties may be approached by mimicking hydrophobic structures created by nature on lotus leaf surface. The lotus effect is based on surface roughness caused by different microstructures together with the hydrophobic properties of the epicuticular wax. The present study investigates the basic principles involved in the fabrication of lotus-like materials on both fibrous and inorganic substrates utilizing the two essential requirements, surface roughness and hydrophobicity. The surface roughness was created either by a porous or a bumpy profile while the hydrophobicity was achieved by grafting a non-fluorinated hydrophobic polymer. For the porous profiles, polymer blend systems showing phase separation were utilized whereas the bumpy profiles were achieved using nanoparticles such as calcium carbonate, silver, or silica particles. In the last part of the research, functionalization of silica nanoparticles was investigated and the development of a universal modification step to obtain the ultrahydrophobic property is reported. In this approach, the adsorption of the polymer and the nanoparticles to fibers has been optimized and the self-cleaning effect of these fabrics modified with silica nanoparticles has also been demonstrated.

  16. Hydrophobic attraction as revealed by AFM force measurements and molecular dynamics simulation.

    Science.gov (United States)

    Fa, Keqing; Nguyen, Anh V; Miller, Jan D

    2005-07-14

    Spherical calcium dioleate particles ( approximately 10 mum in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has a longer range than the DLVO (Derjaguin-Landau-Verwey-Overbeek) prediction. The AFM force between the calcium dioleate sphere and the mineral surfaces does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force and the repulsive hydration force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at calcite- and fluorite-water interfaces as revealed by the numerical computation experiments with molecular dynamics simulation.

  17. Super-hydrophobic film prepared on zinc as corrosion barrier

    International Nuclear Information System (INIS)

    Wang Peng; Zhang Dun; Qiu Ri; Hou Baorong

    2011-01-01

    Research highlights: → Super-hydrophobic film was prepared on zinc surface. → The air trapped in film can dramatically improve the anti-corrosion property. → The air trapped behaves as dielectric for a pure parallel plate capacitor. → The air enhances the contribution of film to the anti-corrosion property. → Without the help of air, the film itself can only present feeble inhibition effect. - Abstract: Potentiostatic electrolysis was carried out to prepare super-hydrophobic film on the surface of metallic zinc. The resultant film was examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical measurements, and contact angle test. The super-hydrophobic property of the film results from the air trapped among the sheets of zinc tetradecanoate. This air behaves as a dielectric for a pure parallel plate capacitor, thereby inhibiting electron transfer between the electrolyte and the substrate. The air can also enhance the contribution of the film itself to protection performance.

  18. Sea level rise, surface warming, and the weakened buffering ability of South China Sea to strong typhoons in recent decades.

    Science.gov (United States)

    Sun, Jingru; Oey, Leo; Xu, F-H; Lin, Y-C

    2017-08-07

    Each year, a number of typhoons in the western North Pacific pass through the Luzon Strait into South China Sea (SCS). Although the storms remain above a warm open sea, the majority of them weaken due to atmospheric and oceanic environments unfavorable for typhoon intensification in SCS, which therefore serves as a natural buffer that shields the surrounding coasts from potentially more powerful storms. This study examines how this buffer has changed over inter-decadal and longer time scales. We show that the buffer weakens (i.e. greater potential for more powerful typhoons) in negative Pacific Decadal Oscillation (PDO) years, as well as with sea-level-rise and surface warming, caused primarily by the deepening of the ocean's 26 °C isotherm Z 26 . A new Intensity Change Index is proposed to describe the typhoon intensity change as a function of Z 26 and other environmental variables. In SCS, the new index accounts for as high as 75% of the total variance of typhoon intensity change.

  19. Strong evidence for enhanced multiple electron capture from surfaces in 46 MeV/u Pb81+ collisions with thin carbon foils.

    Science.gov (United States)

    Bräuning, H; Mokler, P H; Liesen, D; Bosch, F; Franzke, B; Krämer, A; Kozhuharov, C; Ludziejewski, T; Ma, X; Nolden, F; Steck, M; Stöhlker, T; Dunford, R W; Kanter, E P; Bednarz, G; Warczak, A; Stachura, Z; Tribedi, L; Kambara, T; Dauvergne, D; Kirsch, R; Cohen, C

    2001-02-05

    Strong evidence has been found for enhanced multiple electron capture into 46 MeV/u Pb81+ with a significant contribution from the entrance surface of thin carbon foils. Capture of up to five electrons has been observed. The multiple electron capture yield is found to increase with decreasing target thickness for thin targets. A simple model describing the data and showing the importance of capture from surfaces is discussed. Further evidence is found for a pronounced asymmetry between electron capture at the entrance and the exit surfaces. Absolute yields for multiple electron capture and projectile ionization are presented. The experimental total cross sections for single capture and ionization agree well with theory.

  20. On the possible effect of round-the-world surface seismic waves in the dynamics of repeated shocks after strong earthquakes

    Science.gov (United States)

    Zotov, O. D.; Zavyalov, A. D.; Guglielmi, A. V.; Lavrov, I. P.

    2018-01-01

    Based on the observation data for hundreds of the main shocks and thousands of aftershocks, the existence of effect of round-the-world surface seismic waves is demonstrated (let us conditionally refer to them as a round-the-world seismic echo) and the manifestations of this effect in the dynamics of the repeated shocks of strong earthquakes are analyzed. At the same time, we by no means believe this effect has been fully proven. We only present a version of our own understanding of the physical causes of the observed phenomenon and analyze the regularities in its manifestation. The effect is that the surface waves excited in the Earth by the main shock make a full revolution around the Earth and excite a strong aftershock in the epicentral zone of the main shock. In our opinion, the physical nature of this phenomenon consists in the fact that the superposition leads to a concentration of wave energy when the convergent surface waves reach the epicentral zone (cumulative effect). The effect of the first seismic echo is most manifest. Thus, the present work supports our hypothesis of the activation of rock failure under the cumulative impact of an round-the-world seismic echo on the source area which is releasing ("cooling") after the main shock. The spatial regularities in the manifestations of this effect are established, and the independence of the probability of its occurrence on the main shock magnitude is revealed. The effect of a round-the-world seismic echo can be used to improve the reliability of the forecasts of strong aftershocks in determining the scenario for the seismic process developing in the epicentral zone of a strong earthquake that has taken place.

  1. A free-surface hydrodynamic model for density-stratified flow in the weakly to strongly non-hydrostatic regime

    International Nuclear Information System (INIS)

    Shen, Colin Y.; Evans, Thomas E.

    2004-01-01

    A non-hydrostatic density-stratified hydrodynamic model with a free surface has been developed from the vorticity equations rather than the usual momentum equations. This approach has enabled the model to be obtained in two different forms, weakly non-hydrostatic and fully non-hydrostatic, with the computationally efficient weakly non-hydrostatic form applicable to motions having horizontal scales greater than the local water depth. The hydrodynamic model in both its weakly and fully non-hydrostatic forms is validated numerically using exact nonlinear non-hydrostatic solutions given by the Dubriel-Jacotin-Long equation for periodic internal gravity waves, internal solitary waves, and flow over a ridge. The numerical code is developed based on a semi-Lagrangian scheme and higher order finite-difference spatial differentiation and interpolation. To demonstrate the applicability of the model to coastal ocean situations, the problem of tidal generation of internal solitary waves at a shelf-break is considered. Simulations carried out with the model obtain the evolution of solitary wave generation and propagation consistent with past results. Moreover, the weakly non-hydrostatic simulation is shown to compare favorably with the fully non-hydrostatic simulation. The capability of the present model to simulate efficiently relatively large scale non-hydrostatic motions suggests that the weakly non-hydrostatic form of the model may be suitable for application in a large-area domain while the computationally intensive fully non-hydrostatic form of the model may be used in an embedded sub-domain where higher resolution is needed

  2. Recent experimental advances on hydrophobic interactions at solid/water and fluid/water interfaces.

    Science.gov (United States)

    Zeng, Hongbo; Shi, Chen; Huang, Jun; Li, Lin; Liu, Guangyi; Zhong, Hong

    2015-03-15

    Hydrophobic effects play important roles in a wide range of natural phenomena and engineering processes such as coalescence of oil droplets in water, air flotation of mineral particles, and folding and assembly of proteins and biomembranes. In this work, the authors highlight recent experimental attempts to reveal the physical origin of hydrophobic effects by directly quantifying the hydrophobic interaction on both solid/water and fluid/water interfaces using state-of-art nanomechanical techniques such as surface forces apparatus and atomic force microscopy (AFM). For solid hydrophobic surfaces of different hydrophobicity, the range of hydrophobic interaction was reported to vary from ∼10 to >100 nm. With various characterization techniques, the very long-ranged attraction (>100 nm) has been demonstrated to be mainly attributed to nonhydrophobic interaction mechanisms such as pre-existing nanobubbles and molecular rearrangement. By ruling out these factors, intrinsic hydrophobic interaction was measured to follow an exponential law with decay length of 1-2 nm with effective range less than 20 nm. On the other hand, hydrophobic interaction measured at fluid interfaces using AFM droplet/bubble probe technique was found to decay with a much shorter length of ∼0.3 nm. This discrepancy of measured decay lengths is proposed to be attributed to inherent physical distinction between solid and fluid interfaces, which impacts the structure of interface-adjacent water molecules. Direct measurement of hydrophobic interaction on a broader range of interfaces and characterization of interfacial water molecular structure using spectroscopic techniques are anticipated to help unravel the origin of this rigidity-related mismatch of hydrophobic interaction and hold promise to uncover the physical nature of hydrophobic effects. With improved understanding of hydrophobic interaction, intrinsic interaction mechanisms of many biological and chemical pathways can be better

  3. Probing the outstanding local hydrophobicity increase of peptide sequences induced by trifluoromethylated amino acids incorporation.

    Science.gov (United States)

    Gadais, Charlène; Devillers, Emmanuelle; Gasparik, Vincent; Chelain, Evelyne; Pytkowicz, Julien; Brigaud, Thierry

    2018-03-07

    In order to accurately probe the local hydrophobicity increase of peptide sequences by trifluoromethylated amino acids (TfmAAs) incorporation, the chromatographic hydrophobicity indexes (φ0) of three series of tripeptides containing three unnatural trifluoromethylated amino acids have been measured and compared to the indexes of their non-fluorinated analogs. The hydrophobic contribution of each fluorinated amino acids was quantified by varying the position and the protection of (R) and (S)-α-trifluoromethyl alanine (TfmAla), (S)-trifluoromethyl cysteine (TfmCys) and (L)-trifluoromethionine (TFM) in a short peptide sequence. As a general trend, a strong increase of hydrophobicity was precisely measured even exceeding the high hydrophobic contribution of the natural isoleucine amino acid. This study validates the incorporation of trifluoromethylated amino acids into peptide sequences as a rational strategy for the fine tuning of hydrophobic peptide-protein interactions. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Explicit and implicit modeling of nanobubbles in hydrophobic confinement

    Directory of Open Access Journals (Sweden)

    Joachim Dzubiella

    2010-03-01

    Full Text Available Water at normal conditions is a fluid thermodynamically close to the liquid-vapor phase coexistence and features a large surface tension. This combination can lead to interesting capillary phenomena on microscopic scales. Explicit water molecular dynamics (MD computer simulations of hydrophobic solutes, for instance, give evidence of capillary evaporation on nanometer scales, i.e., the formation of nanometer-sized vapor bubbles (nanobubbles between confining hydrophobic surfaces. This phenomenon has been exemplified for solutes with varying complexity, e.g., paraffin plates, coarse-grained homopolymers, biological and solid-state channels, and atomistically resolved proteins. It has been argued that nanobubbles strongly impact interactions in nanofluidic devices, translocation processes, and even in protein stability, function, and folding. As large-scale MD simulations are computationally expensive, the efficient multiscale modeling of nanobubbles and the prediction of their stability poses a formidable task to the'nanophysical' community. Recently, we have presented a conceptually novel and versatile implicit solvent model, namely, the variational implicit solvent model (VISM, which is based on a geometric energy functional. As reviewed here, first solvation studies of simple hydrophobic solutes using VISM coupled with the numerical level-set scheme show promising results, and, in particular, capture nanobubble formation and its subtle competition to local energetic potentials in hydrophobic confinement.Água em condições normais consiste de um fluido termodinamicamente próximo à fase líquida-vapor exibindo alta tensão superficial. Esta combinação conduz a fenômenos capilares interessantes na escala microscópica. Simulações computacionais baseadas em técnicas de Dinâmica Molecular em solutos hidrofóbicos por exemplo fornecem evidências do fenômeno de evaporação capilar em escalas nanométricas dando origem à formação de

  5. Existence of aNew Force in Colloidal Systems Hydrophobic ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 4. Existence of a New Force in Colloidal Systems – Hydrophobic Attraction Between Macroscopic Surfaces. B Sudhir Sanjeev Kumar. General Article Volume 7 Issue 4 April 2002 pp 67-81 ...

  6. Temperature effects on the hydrophobic force between two ...

    Indian Academy of Sciences (India)

    TUHIN SAMANTA

    2018-03-02

    Mar 2, 2018 ... Abstract. Water-mediated, effective, long-range interaction between two hydrophobic surfaces immersed in water is of great importance in natural phenomena. We perform the molecular dynamics simulations to investigate the effect of temperature on the attractive force between two graphene-like ...

  7. Temperature effects on the hydrophobic force between two ...

    Indian Academy of Sciences (India)

    TUHIN SAMANTA

    2018-03-02

    Mar 2, 2018 ... the strength/range of hydrophobic force law (HFL) and on the drying/dewetting transition in terms of num- ber density fluctuations of water confined between two graphene-like surfaces using computer simulations. The organization of the rest of the paper is as follows. In section 2, we present the simulation ...

  8. Development of breathable hydrophobic/hydrophilic functional textiles

    NARCIS (Netherlands)

    Agrawal, P. (Pramod); Brink, G.J. (Ger)

    2013-01-01

    The proposed bi-functional protective structure intended to have hydrophilic interior towards the skin surface and hydrophobic exterior for protection, ensuring fast transfer of moisture between body and external environment. The sandwich structure is prepared using 100% wool jersey and varieties of

  9. Water structure near single and multi-layer nanoscopic hydrophobic ...

    Indian Academy of Sciences (India)

    Wintec

    Abstract. We have performed a series of molecular dynamics simulations of water containing two nano- scopic hydrophobic plates to investigate the modifications of the density and hydrogen bond distributions of water in the vicinity of the surfaces. Our primary goal is to look at the effects of plate thickness, solute–.

  10. Protein-induced bilayer perturbations: Lipid ordering and hydrophobic coupling

    International Nuclear Information System (INIS)

    Petersen, Frederic N.R.; Laursen, Ib; Bohr, Henrik; Nielsen, Claus Helix

    2009-01-01

    The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction between the model protein gramicidin and lipid bilayers of varying thickness. The free energy of the interaction is up to -6 kJ/mol; thus not strongly favored over lipid-lipid interactions. Incorporation of gramicidin results in increased order parameters with increased protein concentration and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few A results in up to 10-fold increased exchange rates as compared to the 'optimal' match situation pointing to the regulatory role of hydrophobic coupling in lipid-protein interactions.

  11. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ...) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No. 68611-0944... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

  12. Structure of Hydrophobically Modified Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Dutcher, John; Katsaras, John

    Phytoglycogen is a highly branched, polysaccharide nanoparticle produced by some varieties of plants including sweet corn. These particles are attractive candidates for cosmetic, industrial and biomedical applications. Many of these applications result from phytoglycogen's unique interaction with water: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Neutron scattering measurements of native phytoglycogen revealed that the particles have uniform size, uniform radial particle density, and a high level of hydration. Hydrophobically modifying the outer surface of the hydrophilic nanoparticles opens up new applications in food and biomedicine, such as solubilizing and stabilizing bioactive compounds. One such modification is octenyl succinate anhydride (OSA), where the hydrophobicity can be tuned by adjusting the degree of substitution. I will present the results of small angle neutron scattering (SANS) measurements of aqueous dispersions of OSA-modified phytoglycogen with two different degrees of modification. Contrast series SANS measurements have yielded information about the radial density profile, providing insight into the nature of the chemical modification of the particles.

  13. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  14. Sorption of acetaminophen, 17alpha-ethynyl estradiol, nalidixic acid, and norfloxacin to silica, alumina. and a hydrophobic medium.

    Science.gov (United States)

    Lorphensri, Oranuj; Intravijit, Jittipong; Sabatini, David A; Kibbey, Tohren C G; Osathaphan, Khemarath; Saiwan, Chintana

    2006-04-01

    Two pure minerals and a hydrophobic medium were selected to study sorption of pharmaceuticals. The sorption of four pharmaceuticals, acetaminophen (analgesic), 17alpha-ethynyl estradiol (synthetic hormone), nalidixic acid (antibiotic), and norfloxacin (antibiotic), was evaluated with silica, alumina, and Porapak P (a hydrophobic medium). Alumina and silica were selected to represent positively charged and negatively charged aquifer mineral surfaces at neutral pH, respectively, while Porapak P was selected to represent the hydrophobic organic content of an aquifer medium. At neutral pH, acetaminophen, the least hydrophobic pharmaceutical, showed no significant sorption to any of the media, while 17alpha-ethynyl estradiol, the most hydrophobic pharmaceutical, showed significant sorption to Porapak P. Nalidixic acid, which has a carboxyl functional group that is anionic at neutral pH, showed significant adsorption to the positively charged alumina. Norfloxacin, with both a carboxyl (anionic) and a piperazynyl (cationic) group, can exist in four forms (neutral, cationic, anionic, and zwitterionic) depending on the aqueous pH. Norfloxacin also showed significant adsorption than nalidixic acid. Both nalidixic acid and norfloxacin adsorbed to silica and Porapak P to a much lower extent. The pH dependence of nalidixic acid and norfloxacin adsorption to silica and alumina was also studied by varying the pH between 4 and 11. The maximum adsorption of nalidixic acid to alumina occurred near its pKa (pH approximately 6), where the combination of cationic alumina and anionic nalidixic produced maximum adsorption. The maximum adsorption of norfloxacin to alumina was observed at pH approximately 7, which was the region where the zwitterionic form dominated. This research demonstrates that the adsorption of ionizable pharmaceuticals is strongly dependent on the system pH, the pharmaceutical properties (pKa and hydrophobicity), and the nature of the surface charge (point of zero

  15. A Natural Based Method for Hydrophobic Treatment of Natural Fiber Material.

    Science.gov (United States)

    Kick, Thomas; Grethe, Thomas; Mahltig, Boris

    2017-06-01

    A treatment for hydrophobic functionalization of natural fiber materials is developed. This hydrophobic treatment is based mainly on natural products. As hydrophobic component the natural Tung Oil is used, which is originally a compound used for wood conservation purposes. The application on textile is done in a padding process under presence of an oxidative agent. For the current investigations a fiber felt from linen was used. The hydrophobic effect is determined by the concentration of Tung Oil and the duration of a thermal drying process. The hydrophobic effect is investigated by capillary rise tests and contact angle measurements. Scanning electron microscopy SEM is used to investigate the surface topography of the fiber material and the deposited hydrophobic material. Altogether, an interesting and promising method for hydrophobisation of natural fibers is developed, which could especially be used as part of a production process of a fiber reinforced composite material, mainly based on natural products.

  16. Hydrophobic-Core Microcapsules and Their Formation

    Science.gov (United States)

    Calle, Luz M. (Inventor); Li, Wenyan (Inventor); Buhrow, Jerry W. (Inventor); Jolley, Scott T. (Inventor)

    2016-01-01

    Hydrophobic-core microcapsules and methods of their formation are provided. A hydrophobic-core microcapsule may include a shell that encapsulates a hydrophobic substance with a core substance, such as dye, corrosion indicator, corrosion inhibitor, and/or healing agent, dissolved or dispersed therein. The hydrophobic-core microcapsules may be formed from an emulsion having hydrophobic-phase droplets, e.g., containing the core substance and shell-forming compound, dispersed in a hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

  17. Photoemission mechanism of water-soluble silver nanoclusters: ligand-to-metal-metal charge transfer vs strong coupling between surface plasmon and emitters.

    Science.gov (United States)

    Chen, Yuting; Yang, Taiqun; Pan, Haifeng; Yuan, Yufeng; Chen, Li; Liu, Mengwei; Zhang, Kun; Zhang, Sanjun; Wu, Peng; Xu, Jianhua

    2014-02-05

    Using carboxylate-protected silver nanoclusters (Ag-carboxylate NCs) as a model, we separately investigated the contribution of the ligand shell and the metal core to understand the nature of photoluminescence of Ag NCs. A new Ag(0)NCs@Ag(I)-carboxylate complex core-shell structural model has been proposed. The emission from the Ag-carboxylate NCs could be attributed to ligand-to-metal-metal charge transfer from Ag(I)-carboxylate complexes (the oxygen atom in the carboxylate ligands to the Ag(I) ions) to the Ag atoms and subsequent radiative relaxation. Additionally, we found that the emission wavelength of the Ag NCs depends on the excitation wavelength implying a strong coupling between surface plasmon and emitter in Ag NCs. The strong coupling between the surface plasmon and the emitter determines the quantum yield and lifetime. The emission mechanism of Ag NCs and its relation to the organic templates and metal cores were clearly clarified. The results should stimulate additional experimental and theoretical research on the molecular-level design of luminescent metal probes for optoelectronics and other applications.

  18. Nanoscale morphology for high hydrophobicity of a hard sol-gel thin film

    International Nuclear Information System (INIS)

    Wu, Y.L.; Chen, Z.; Zeng, X.T.

    2008-01-01

    It is challenging to obtain a hydrophobic smooth coating with high optical and mechanical properties at the same time because the hydrophobic additives are soft in nature resulting in reduced hardness and durability. This paper reports a durable hydrophobic transparent coating on glass fabricated by sol-gel technology and a low volume medium pressure (LVMP) spray process. The sol-gel formula consists of a pre-linked hydrophobic nano-cluster from hydroxyl-terminated polydimethylsiloxane, titanium tetraisopropoxide and a silica-based sol-gel matrix with silica hard fillers. Polydimethylsiloxane (PDMS) is uniformly distributed throughout the coating layer providing durable hydrophobic property. Mechanical properties are achieved by the hard matrix and hard fillers with the nano-structures. Due to the surface nano-morphology, a high degree of hydrophobicity was maintained with only 10 vol.% PDMS, while the hardness and abrasion resistance of the coatings were not significantly compromised. Chemical analyses by FTIR confirmed the uniform distribution of the PDMS and surface morphology analyses by atomic force microscopy (AFM) displayed the nano-surface structures that enhanced the hydrophobicity. The special surface nanostructures can be quantified using surface Kurtosis and ratio between asperity peak height to distance between peaks. The LVMP process influences the spray droplet size resulting in different surface structures

  19. Nanoscale morphology for high hydrophobicity of a hard sol-gel thin film

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.L. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore)], E-mail: ylwu@simtech.a-star.edu.sg; Chen, Z. [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Zeng, X.T. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore)

    2008-08-30

    It is challenging to obtain a hydrophobic smooth coating with high optical and mechanical properties at the same time because the hydrophobic additives are soft in nature resulting in reduced hardness and durability. This paper reports a durable hydrophobic transparent coating on glass fabricated by sol-gel technology and a low volume medium pressure (LVMP) spray process. The sol-gel formula consists of a pre-linked hydrophobic nano-cluster from hydroxyl-terminated polydimethylsiloxane, titanium tetraisopropoxide and a silica-based sol-gel matrix with silica hard fillers. Polydimethylsiloxane (PDMS) is uniformly distributed throughout the coating layer providing durable hydrophobic property. Mechanical properties are achieved by the hard matrix and hard fillers with the nano-structures. Due to the surface nano-morphology, a high degree of hydrophobicity was maintained with only 10 vol.% PDMS, while the hardness and abrasion resistance of the coatings were not significantly compromised. Chemical analyses by FTIR confirmed the uniform distribution of the PDMS and surface morphology analyses by atomic force microscopy (AFM) displayed the nano-surface structures that enhanced the hydrophobicity. The special surface nanostructures can be quantified using surface Kurtosis and ratio between asperity peak height to distance between peaks. The LVMP process influences the spray droplet size resulting in different surface structures.

  20. Friction and Adhesion Forces of Bacillus thuringiensis Spores on Planar Surfaces in Atmospheric Systems

    Energy Technology Data Exchange (ETDEWEB)

    Kweon, Hyojin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2011-11-07

    The kinetic friction force and the adhesion force of Bacillus thuringiensis spores on planar surfaces in atmospheric systems were studied using atomic force microscopy. The influence of relative humidity (RH) on these forces varied for different surface properties including hydrophobicity, roughness, and surface charge. The friction force of the spore was greater on a rougher surface than on mica, which is atomically flat. As RH increases, the friction force of the spores decreases on mica whereas it increases on rough surfaces. The influence of RH on the interaction forces between hydrophobic surfaces is not as strong as for hydrophilic surfaces. The friction force of the spore is linear to the sum of the adhesion force and normal load on the hydrophobic surface. In conclusion, the poorly defined surface structure of the spore and the adsorption of contaminants from the surrounding atmosphere are believed to cause a discrepancy between the calculated and measured adhesion forces.

  1. Hydrophobicity and charge shape cellular metabolite concentrations.

    Directory of Open Access Journals (Sweden)

    Arren Bar-Even

    2011-10-01

    Full Text Available What governs the concentrations of metabolites within living cells? Beyond specific metabolic and enzymatic considerations, are there global trends that affect their values? We hypothesize that the physico-chemical properties of metabolites considerably affect their in-vivo concentrations. The recently achieved experimental capability to measure the concentrations of many metabolites simultaneously has made the testing of this hypothesis possible. Here, we analyze such recently available data sets of metabolite concentrations within E. coli, S. cerevisiae, B. subtilis and human. Overall, these data sets encompass more than twenty conditions, each containing dozens (28-108 of simultaneously measured metabolites. We test for correlations with various physico-chemical properties and find that the number of charged atoms, non-polar surface area, lipophilicity and solubility consistently correlate with concentration. In most data sets, a change in one of these properties elicits a ~100 fold increase in metabolite concentrations. We find that the non-polar surface area and number of charged atoms account for almost half of the variation in concentrations in the most reliable and comprehensive data set. Analyzing specific groups of metabolites, such as amino-acids or phosphorylated nucleotides, reveals even a higher dependence of concentration on hydrophobicity. We suggest that these findings can be explained by evolutionary constraints imposed on metabolite concentrations and discuss possible selective pressures that can account for them. These include the reduction of solute leakage through the lipid membrane, avoidance of deleterious aggregates and reduction of non-specific hydrophobic binding. By highlighting the global constraints imposed on metabolic pathways, future research could shed light onto aspects of biochemical evolution and the chemical constraints that bound metabolic engineering efforts.

  2. Design, construction, and characterization of a second-generation DARP in library with reduced hydrophobicity.

    Science.gov (United States)

    Seeger, Markus A; Zbinden, Reto; Flütsch, Andreas; Gutte, Petrus G M; Engeler, Sibylle; Roschitzki-Voser, Heidi; Grütter, Markus G

    2013-09-01

    Designed ankyrin repeat proteins (DARPins) are well-established binding molecules based on a highly stable nonantibody scaffold. Building on 13 crystal structures of DARPin-target complexes and stability measurements of DARPin mutants, we have generated a new DARPin library containing an extended randomized surface. To counteract the enrichment of unspecific hydrophobic binders during selections against difficult targets containing hydrophobic surfaces such as membrane proteins, the frequency of apolar residues at diversified positions was drastically reduced and substituted by an increased number of tyrosines. Ribosome display selections against two human caspases and membrane transporter AcrB yielded highly enriched pools of unique and strong DARPin binders which were mainly monomeric. We noted a prominent enrichment of tryptophan residues during binder selections. A crystal structure of a representative of this library in complex with caspase-7 visualizes the key roles of both tryptophans and tyrosines in providing target contacts. These aromatic and polar side chains thus substitute the apolar residues valine, leucine, isoleucine, methionine, and phenylalanine of the original DARPins. Our work describes biophysical and structural analyses required to extend existing binder scaffolds and simplifies an existing protocol for the assembly of highly diverse synthetic binder libraries. © 2013 The Protein Society.

  3. Evaluation of Sulfonate-Based Collectors with Different Hydrophobic Tails for Flotation of Fluorite

    Directory of Open Access Journals (Sweden)

    Renji Zheng

    2018-02-01

    Full Text Available This investigation aims to demonstrate the effects of hydrophobic tails on the affinity and relevant flotation response of sulfonate-based collectors for fluorite. For this purpose, a series of alkyl sulfonates with different hydrophobic tails, namely sodium decanesulfonate (C10, sodium dodecylsulfate (C12, sodium hexadecanesulfonate (C16, and sodium dodecylbenzenesulfonate (C12B were applied. The flotation tests showed that C12 and C12B had a better collecting performance than C10 and C16 at pH < 10, and the flotation recovery of fluorite was higher when adopting C12B as a collector compared with C12 with a strong base. The adsorption behaviors of collectors on the fluorite surface were studied through zeta potential, Fourier transform infrared (FTIR, and X-ray photoelectron spectroscopy (XPS analyses. It was found that the affinity of alkyl sulfonates for fluorite was enhanced with the increase of the alkyl chain length from C10 to C16. The existence of phenyl in the hydrophobic tail of sulfonates could improve its activity for fluorite by reducing its surface tension. The abnormal phenomenon C16 with a high affinity for fluorite had a low collecting performance for fluorite mainly due to its overlong alkyl chain, resulting in low solubility in pulp, which restrained its interaction with fluorite. We concluded that C12B was the most applicable collector for fluorite among these reagents due to its high activity, high solubility, and low cost, which was further substantiated by calculating their molecular frontier orbital energy.

  4. Fabrication of super-hydrophobic duo-structures

    Science.gov (United States)

    Zhang, X. Y.; Zhang, F.; Jiang, Y. J.; Wang, Y. Y.; Shi, Z. W.; Peng, C. S.

    2015-04-01

    Recently, super-hydrophobicity has attracted increasing attention due to its huge potential in the practical applications. In this paper, we have presented a duo-structure of the combination of micro-dot-matrix and nano-candle-soot. Polydimethylsiloxane (PDMS) was used as a combination layer between the dot-matrix and the soot particles. Firstly, a period of 9-μm dot-matrix was easily fabricated on the K9 glass using the most simple and mature photolithography process. Secondly, the dot-matrix surface was coated by a thin film of PDMS (elastomer: hardener=10:1) which was diluted by methylbenzene at the volume ratio of 1:8. Thirdly, we held the PDMS modified surface over a candle flame to deposit a soot layer and followed by a gentle water-risen to remove the non-adhered particles. At last, the samples were baked at 85°C for 2 hours and then the duo-structure surface with both micro-size dot-matrix and nano-size soot particles was obtained. The SEM indicated this novel surface morphology was quite like a lotus leaf of the well-know micro-nano-binary structures. As a result, the contact angle meter demonstrated such surface exhibited a perfect super-hydrophobicity with water contact angle of 153° and sliding angle of 3°. Besides, just listed as above, the fabrication process for our structure was quite more easy, smart and low-cost compared with the other production technique for super-hydrophobic surfaces such as the phase separation method, electrochemical deposition and chemical vapor deposition etc. Hence, this super-hydrophobic duo-structure reported in this letter was a great promising candidate for a wide and rapid commercialization in the future.

  5. Super-Hydrophobic Green Corrosion Inhibitor On Carbon Steel

    Science.gov (United States)

    Hassan, H.; Ismail, A.; Ahmad, S.; Soon, C. F.

    2017-06-01

    There are many examples of organic coatings used for corrosion protection. In particular, hydrophobic and super-hydrophobic coatings are shown to give good protection because of their enhanced ability to slow down transport of water and ions through the coating. The purpose of this research is to develop water repellent coating to avoid direct contact between metal and environment corrosive and mitigate corrosion attack at pipeline system. This water repellent characteristic on super-hydrophobic coating was coated by electrodeposition method. Wettability of carbon steel with super-hydrophobic coating (cerium chloride and myristic acid) and oxidized surface was investigated through contact angle and inhibitor performance test. The inhibitor performance was studied in 25% tannin acid corrosion test at 30°C and 3.5% sodium chloride (NaCl). The water contact angle test was determined by placing a 4-μL water droplet of distilled water. It shows that the wettability of contact angle super-hydrophobic with an angle of 151.60° at zero minute can be classified as super-hydrophobic characteristic. By added tannin acid as inhibitor the corrosion protection on carbon steel becomes more consistent. This reveals that the ability of the coating to withstand with the corrosion attack in the seawater at different period of immersions. The results elucidate that the weight loss increased as the time of exposure increased. However, the corrosion rates for uncoated carbon steel is high compared to coated carbon steel. As a conclusion, from both samples it can be seen that the coated carbon steel has less corrosion rated compared to uncoated carbon steel and addition of inhibitor to the seawater provides more protection to resist corrosion attack on carbon steel.

  6. Adsorption of Hydrophobically Modified Polyelectrolytes on Hydrophobic Substrates Adsorption de polyélectrolytes modifiés hydrophobiquement sur les substrats hydrophobes

    Directory of Open Access Journals (Sweden)

    Mays J. W.

    2006-12-01

    Full Text Available A series of diblock copolymers, poly (tert-butyl styrene-sodium poly (styrene sulfonate with different molecular weight and percentage of sulfonation have been used to study the effect of polymer structure on its adsorption behavior onto hydrophobically modified silicon wafers. The percentage of the hydrophobic block varies from 3. 6-8. 9%. Previous studies show that salt concentration is very important for the adsorption of such polyelectrolytes onto silica surfaces. Octadecyltriethoxysilane (OTE has been used to modify the silicon wafer which changes the water contact angle from 50° on unmodified silica to 100° to 120°. On this hydrophobic surface, we found that the adsorption of these slightly hydrophobically modified polyelectrolytes is close to the 4/23rd power of salt concentration predicted by a recent model. The grafting density is also consistent with a dependence on the length of the hydrophobic block to the -12/23rd power, and the length of the polyelectrolyte block to the -6/23rd power, predicted by this model. Une série de copolymères à diblocs poly (tert-butyle styrène-sodium (sulfonate de polystyrène de masses moléculaires et pourcentages de sulfonation différents ont été utilisés pour étudier les effets de la structure du polymère sur son pouvoir d'adsorption sur des surfaces de silicium modifiées hydrophobiquement. Le pourcentage du bloc hydrophobe varie de 3,6 à 8,9%. Les études antérieures montrent que la concentration saline est très importante pour l'adsorption de ces polyélectrolytes sur les surfaces de silice. Nous avons utilisé l'octadecyltriéthoxysilane (OTE pour modifier la surface de silicium qui change l'angle de contact de l'eau de 50° sur la silice non modifiée à une valeur comprise entre 100° et 120° sur la silice modifiée. Sur cette surface hydrophobe, nous constatons que l'adsorption de ces polyélectrolytes légèrement modifiés hydrophobiquement est proche de la loi puissance 4

  7. The role of Rabi splitting tuning in the dynamics of strongly coupled J-aggregates and surface plasmon polaritons in nanohole arrays.

    Science.gov (United States)

    Wang, Hai; Toma, Andrea; Wang, Hai-Yu; Bozzola, Angelo; Miele, Ermanno; Haddadpour, Ali; Veronis, Georgios; De Angelis, Francesco; Wang, Lei; Chen, Qi-Dai; Xu, Huai-Liang; Sun, Hong-Bo; Zaccaria, Remo Proietti

    2016-07-21

    We have investigated the influence of Rabi splitting tuning on the dynamics of strongly coupled J-aggregate/surface plasmon polariton systems. In particular, the Rabi splitting was tuned by modifying the J-aggregate molecule concentration while a polaritonic system was provided by a nanostructure formed by holes array in a golden layer. From the periodic and concentration changes we have identified, through numerical and experimental steady-state analyses, the best geometrical configuration for maximizing Rabi splitting, which was then used for transient absorption measurements. It was found that in transient absorption spectra, under upper band excitation, two bleaching peaks appear when a nanostructured polaritonic pattern is used. Importantly, their reciprocal distance increases upon increase of J-aggregate concentration, a result confirmed by steady-state analysis. In a similar manner it was also found that the lifetime of the upper band is intimately related to the coupling strength. In particular, we argue that with strong coupling strength, i.e. high J-aggregate concentration, a short lifetime of the upper band has to be expected due to the suppression of the bottleneck effect. This result supports the idea that the dynamics of hybrid systems is profoundly dependent on Rabi splitting.

  8. Hydrophobic solvation of nonspherical solutes

    International Nuclear Information System (INIS)

    Pratt, L.R.; Chandler, D.

    1980-01-01

    The theory of hydrophobic effects presented by Pratt and Chandler is generalized to include nonpolar solutes which are distinctly aspherical. The theory is used to study the solvation of simple aspherical hydrocarbon solutes in liquid water. The radial solvation of each component of diatomiclike solutes is studied as a function of their separation, or bond length. From these results it is found that when the bond length is large enough that one water molecule can fit between the apolar pair, the radial solvation of each is the same as that when the bond length approaches infinity. The solvation of the various sites of the homologous series methane, ethane, propane, and n-butane is also studied, and effects of the geometrical structure of the solutes on their solvation is discussed

  9. Impact of a Hydrophobic Sphere onto a Bath

    Science.gov (United States)

    Harris, Daniel M.; Edmonds, John; Galeano-Rios, Carlos A.; Milewski, Paul A.

    2017-11-01

    Small hydrophobic particles impacting a water surface can rebound completely from the interface (Lee & Kim, Langmuir, 2008). In the present work, we focus on the bouncing dynamics of millimetric hydrophobic spheres impacting the surface of a quiescent water bath. Particular attention is given to the dependence of the normal coefficient of restitution and contact time on the impact velocity and the radius and density of the sphere. Our experimental observations are compared to the predictions of a fluid model derived from linearized Navier-Stokes under the assumption of a high Reynolds number regime (Galeano-Rios et al., JFM, in press). In the model, the motions of the sphere and the fluid interface are found by imposing the natural geometric and kinematic compatibility conditions. Future directions will be discussed. C.A.G.-R. and P.A.M. gratefully acknowledge support through the EPSRC project EP/N018176/1.

  10. Nanoscale encapsulation: the structure of cations in hydrophobic microporous aluminosilicates

    International Nuclear Information System (INIS)

    Wasserman, S.R.; Yuchs, S.E.; Giaquinta, D.; Soderholm, L.; Song, Kang.

    1996-01-01

    Hydrophobic microporous aluminosilicates, created by organic surface modification of inherently hydrophilic materials such as zeolites and clays, are currently being investigated as storage media for hazardous cations. Use of organic monolayers to modify the surface of an aluminosilicate after introducing an ion into the zeolite/clay reduces the interaction of water with the material. Resulting systems are about 20 times more resistant to leaching of stored ion. XAS spectra from the encapsulated ion demonstrate that byproducts from the organic modifier can complex with the stored cation. This complexation can result in a decreased affinity of the cation for the aluminosilicate matrix. Changing the organic modifier eliminates this problem. XAS spectra also indicate that the reactivity and speciation of the encapsulated ion may change upon application of the hydrophobic layer

  11. Biomimetic solution against dewetting in a highly hydrophobic nanopore.

    Science.gov (United States)

    Picaud, Fabien; Paris, Guillaume; Gharbi, Tijani; Balme, Sébastien; Lepoitevin, Mathilde; Tangaraj, Vidhyadevi; Bechelany, Mikhael; Janot, Jean Marc; Balanzat, Emmanuel; Henn, François

    2016-06-14

    A water molecule is the foundation of life and is the primary compound in every living system. While many of its properties are understood in a bulk solvent, its behavior in a small hydrophobic nanopore still raises fundamental questions. For instance, a wetting/dewetting transition in a hydrophobic solid-state or a polymer nanopore occurs stochastically and can only be prevented by external physical stimuli. Controlling these transitions would be a primary requirement to improve many applications. Some biological channels, such as gramicidin A (gA) proteins, show a high rate of water and ion diffusion in their central subnanochannel while their external surface is highly hydrophobic. The diameter of this channel is significantly smaller than the inner size of the lowest artificial nanopore in which water drying occurs (i.e. 1.4 nm). In this paper, we propose an innovative idea to generate nanopore wetting as a result of which the application of an external field is no longer required. In a nanopore, the drying or wetting of the inner walls occurs randomly (in experiments and in simulations). However, we have shown how the confinement of gA, in a dried hydrophobic nanopore, rapidly generates a stable wetting of the latter. We believe that this simple idea, based on biomimetism, could represent a real breakthrough that could help to improve and develop new nanoscale applications.

  12. Preparation of alveolate hydrophobic catalyst for tritium waste gas treatment

    International Nuclear Information System (INIS)

    Yang, Yong; Peng, Shuming; Wang, Heyi; Du, Yang; Li, Jiamao

    2016-01-01

    Highlights: • The catalyst is hydrophobic, it will not be poisoned by steam in room air at room temperature which is better than Pt-Al 2 O 3 . • At room temperature, the conversion of low concentration of H2 and tritium gas in room air over the catalyst is high. • The air resistance of catalyst is much lower than graininess Pt-Al 2 O 3 . • It is inorganic and will not burn. - Abstract: To prepare a catalyst for the detritiation of waste gases at high flow rates, a heat-resistant hydrophobic zeolitic molecular sieve coating was synthesized on the surface of alveolate cordierite by hydrothermal processing. The alveolate hydrophobic catalyst prepared from the support was essentially waterproof and not easily poisoned by moisture. At room temperature, the conversion of low concentrations of H 2 in humid air over the catalyst was higher than 95% at different space velocities (0–16,000 h −1 ) and different relative humidities. The reaction rate constant of the oxidation of tritium over alveolate hydrophobic catalyst is 0.182 s −1 at 293.3 K–293.7 K and 59%–60% RH, it is much higher than the catalyst of reference honeycomb catalyst.

  13. Fabrication of corona-free nanoparticles with tunable hydrophobicity.

    Science.gov (United States)

    Moyano, Daniel F; Saha, Krishnendu; Prakash, Gyan; Yan, Bo; Kong, Hao; Yazdani, Mahdieh; Rotello, Vincent M

    2014-07-22

    A protein corona is formed at the surface of nanoparticles in the presence of biological fluids, masking the surface properties of the particle and complicating the relationship between chemical functionality and biological effects. We present here a series of zwitterionic NPs of variable hydrophobicity that do not adsorb proteins at moderate levels of serum protein and do not form hard coronas at physiological serum concentrations. These particles provide platforms to evaluate nanobiological behavior such as cell uptake and hemolysis dictated directly by chemical motifs at the nanoparticle surface.

  14. AFCo1, a meningococcal B-derived cochleate adjuvant, strongly enhances antibody and T-cell immunity against Plasmodium falciparum merozoite surface protein 4 and 5

    Directory of Open Access Journals (Sweden)

    Pérez Oliver

    2009-02-01

    Full Text Available Abstract Background Whilst a large number of malaria antigens are being tested as candidate malaria vaccines, a major barrier to the development of an effective vaccine is the lack of a suitable human adjuvant capable of inducing a strong and long lasting immune response. In this study, the ability of AFCo1, a potent T and B cell adjuvant based on cochleate structures derived from meningococcal B outer membrane proteoliposomes (MBOMP, to boost the immune response against two Plasmodium falciparum antigens, merozoite surface protein 4 (MSP4 and 5 (MSP5, was evaluated. Methods Complete Freund's adjuvant (CFA, which is able to confer protection against malaria in animal MSP4/5 vaccine challenge models, was used as positive control adjuvant. MSP4 and 5-specific IgG, delayed-type hypersensitivity (DTH, T-cell proliferation, and cytokine production were evaluated in parallel in mice immunized three times intramuscularly with MSP4 or MSP5 incorporated into AFCo1, synthetic cochleate structures, CFA or phosphate buffered saline. Results AFCo1 significantly enhanced the IgG and T-cell response against MSP4 and MSP5, with a potency equivalent to CFA, with the response being characterized by both IgG1 and IgG2a isotypes, increased interferon gamma production and a strong DTH response, consistent with the ability of AFCo1 to induce Th1-like immune responses. Conclusion Given the proven safety of MBOMP, which is already in use in a licensed human vaccine, AFCo1 could assist the development of human malaria vaccines that require a potent and safe adjuvant.

  15. AFCo1, a meningococcal B-derived cochleate adjuvant, strongly enhances antibody and T-cell immunity against Plasmodium falciparum merozoite surface protein 4 and 5.

    Science.gov (United States)

    Bracho, Gustavo; Zayas, Caridad; Wang, Lina; Coppel, Ross; Pérez, Oliver; Petrovsky, Nikolai

    2009-02-27

    Whilst a large number of malaria antigens are being tested as candidate malaria vaccines, a major barrier to the development of an effective vaccine is the lack of a suitable human adjuvant capable of inducing a strong and long lasting immune response. In this study, the ability of AFCo1, a potent T and B cell adjuvant based on cochleate structures derived from meningococcal B outer membrane proteoliposomes (MBOMP), to boost the immune response against two Plasmodium falciparum antigens, merozoite surface protein 4 (MSP4) and 5 (MSP5), was evaluated. Complete Freund's adjuvant (CFA), which is able to confer protection against malaria in animal MSP4/5 vaccine challenge models, was used as positive control adjuvant. MSP4 and 5-specific IgG, delayed-type hypersensitivity (DTH), T-cell proliferation, and cytokine production were evaluated in parallel in mice immunized three times intramuscularly with MSP4 or MSP5 incorporated into AFCo1, synthetic cochleate structures, CFA or phosphate buffered saline. AFCo1 significantly enhanced the IgG and T-cell response against MSP4 and MSP5, with a potency equivalent to CFA, with the response being characterized by both IgG1 and IgG2a isotypes, increased interferon gamma production and a strong DTH response, consistent with the ability of AFCo1 to induce Th1-like immune responses. Given the proven safety of MBOMP, which is already in use in a licensed human vaccine, AFCo1 could assist the development of human malaria vaccines that require a potent and safe adjuvant.

  16. Strongly Correlated Topological Insulators

    Science.gov (United States)

    2016-02-03

    Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials...in which a topologically nontrivial quasi-flat band is fractionally filled and then subject to strong interactions. The views, opinions and/or

  17. Hydrophobicity of hemp shiv treated with sol-gel coatings

    Science.gov (United States)

    Hussain, Atif; Calabria-Holley, Juliana; Schorr, Diane; Jiang, Yunhong; Lawrence, Mike; Blanchet, Pierre

    2018-03-01

    This is the first time sol-gel technology is used in the treatment of hemp shiv to develop sustainable thermal insulation building materials. The impact on the hydrophobicity of hemp shiv by depositing functionalised sol-gel coatings using hexadecyltrimethoxysilane (HDTMS) has been investigated. Bio-based materials have tendency to absorb large amounts of water due to their hydrophilic nature and highly porous structure. In this work, the influence of catalysts, solvent dilution and HDTMS loading in the silica sols on the hydrophobicity of hemp shiv surface has been reported. The hydrophobicity of sol-gel coated hemp shiv increased significantly when using acid catalysed sols which provided water contact angles of up to 118° at 1% HDTMS loading. Ethanol diluted sol-gel coatings enhanced the surface roughness of the hemp shiv by 36% as observed under 3D optical profilometer. The XPS results revealed that the surface chemical composition of the hemp shiv was altered by the sol-gel coating, blocking the hydroxyl sites responsible for hydrophilicity.

  18. Construction of mechanically durable superhydrophobic surfaces by thermal spray deposition and further surface modification

    Science.gov (United States)

    Chen, Xiuyong; Gong, Yongfeng; Suo, Xinkun; Huang, Jing; Liu, Yi; Li, Hua

    2015-11-01

    Here we report a simple and cost-effective technical route for constructing superhydrophobic surfaces with excellent abrasion resistance on various substrates. Rough surface structures were fabricated by thermal spray deposition of a variety of inorganic materials, and further surface modification was made by applying a thin layer of polytetrafluoroethylene. Results show that the Al, Cu, or NiCrBSi coatings with the surface roughness of up to 13.8 μm offer rough surface profile to complement the topographical morphology in micro-/nano-scaled sizes, and the hydrophobic molecules facilitate the hydrophobicity. The contact angles of water droplets of ∼155° with a sliding angle of up to 3.5° on the samples have been achieved. The newly constructed superhydrophobic coatings tolerate strong abrasion, giving clear insight into their long-term functional applications.

  19. In-line gas chromatographic apparatus for measuring the hydrophobic micropore volume (HMV) and contaminant transformation in mineral micropores.

    Science.gov (United States)

    Cheng, Hefa; Reinhard, Martin

    2010-07-15

    Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of TCE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch's rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microporous solids and investigating contaminant-solid interactions. 2010 Elsevier B.V. All rights reserved.

  20. Salt creep and wicking counteract hydrophobic organic structures

    Science.gov (United States)

    Burkhardt, Juergen

    2017-04-01

    The hydrophobic nature of many biological and edaphic surfaces prevents wetting and water movement. Already small amounts of salts and other hygroscopic material (e.g. by aerosol deposition to leaf surfaces) may change this situation. Salts attract minute amounts of liquid water to the surface and may dynamically expand on the original surface by creeping (evaporation-driven extension of crystals). Creeping is governed by fluctuations of relative humidity and increases with time. Under high, almost saturated concentrations of the salt solutions, ions from the chaotropic side of the Hofmeister series creep most efficiently. Once established, continuous salt connections may act to channel small water flows along the surface. They may act as wicks if water is removed from one side by evaporation. Stomata may in this way become 'leaky' by the leaf surface accumulation of hygroscopic aerosols.

  1. Durable PROX catalyst based on gold nanoparticles and hydrophobic silica

    KAUST Repository

    Laveille, Paco

    2016-01-20

    3 nm gold nanoparticles (Au NP) obtained by direct chemical reduction of AuPPh3Cl in the presence of methyl-terminated silica exhibit superior durability for low temperature CO oxidation in the presence of hydrogen (PROX). The activity of hydrophobic Au/SiO2-R972 indeed appears much more stable with time-on-stream than those of the OH-terminated, hydrophilic Au/TiO2 and Au/Al2O3 catalysts, with similar Au NP size. This enhanced stability is attributed to the peculiar catalyst surface of Au/SiO2-R972. Not only may the support hydrophobicity concentrate and facilitate reactant adsorption and product desorption over Au NP, but methyl-terminated SiO2-R972 likely also inhibits carbonatation of the Au/support interface. Hence, at a temperature at which H2/H2O “cleaning” of the carbonate-contaminated Au/Al2O3 and Au/TiO2 surface is inefficient (< 100°C), passivated Au/SiO2-R972 displays much more stable PROX activity. Besides, the virtual absence of surface hydroxyl groups, which provide sites for water formation in H2/O2 atmospheres, can also account for the improved PROX selectivity (>85%) observed over Au/SiO2-R972. This new example, of CO oxidation activity of gold nanoparticles dispersed over a hydrophobic, “inert” support, clearly emphasizes the role of hydrogen as a promoter for the gold-catalyzed oxidation of CO at low temperature. Unlike support-mediated oxygen activation, hydrogen-only mediated oxygen activation takes full advantage of the hydrophobic surface, which is much more resistant against CO2 and thus remains free of poisonous carbonate species, as compared with hydroxyl-terminated catalysts. Hence, although the absence of surface hydroxyl groups prevents the hydrophobic Au/SiO2-R972 catalyst to reach the state-of-the-art activities initially displayed by Au/TiO2 and Au/Al2O3, it brings long-term stability with time-on-stream and superior selectivity, which opens up promising perspectives in the development of viable PROX catalysts based on gold.

  2. Automated food microbiology: potential for the hydrophobic grid-membrane filter.

    Science.gov (United States)

    Sharpe, A N; Diotte, M P; Dudas, I; Michaud, G L

    1978-07-01

    Bacterial counts obtained on hydrophobic grid-membrane filters were comparable to conventional plate counts for Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus in homogenates from a range of foods. The wide numerical operating range of the hydrophobic grid-membrane filters allowed sequential diluting to be reduced or even eliminated, making them attractive as components in automated systems of analysis. Food debris could be rinsed completely from the unincubated hydrophobic grid-membrane filter surface without affecting the subsequent count, thus eliminating the possibility of counting food particles, a common source of error in electronic counting systems.

  3. Hydrophobically Modified Glycol Chitosan Nanoparticles for Targeting Breast Cancer Microcalcification Using Alendronate Probes

    Science.gov (United States)

    Vishnu, Kamalakannan

    In 2016, invasive breast cancer was diagnosed in about 246,660 women and 2,600 men. An additional 61,000 new cases of in situ breast cancer was diagnosed in women. Microcalcifications are most common abnormalities detected by mammography for breast cancer, present in about 30% of all malignant breast lesions. Tumor specific biomarkers are used for targeting these abnormalities. Nanoparticles with multimodal and combinatorial therapies and conjunction of bio-ligands for specific molecular targeting using surface modifications effectually deliver a variety of drugs and are simultaneously used to image tumor progression. Alendronate, a germinal bisphosphonate conjugation as a targeting ligand would improve the nanoparticle's direct binding to hydroxyapatite (HA) mimicking calcified spots in breast cancer lesions. In this study, the hydrophobically modified glycol chitosan (HGC) micelle was modified with alendronate surface functionalization using a biotin-avidin interaction to improve the nanomicelle's calcification targeting ability. Biotinylated, avidinlyated hydrophobically modified iv glycol chitosan particles were linked to biotinylated alendronate via a strong biotin-avidin linkage. Cyanine 3, a red fluorescent dye was conjugated to the amine groups on HGC for visualization of micelles. The size of the nanoparticles measured was 254.0 +/- 0.43 nm and 209.7 +/- 1.0 nm for Cy3- BHGCA and Cy3-BHGCA-BALN nanoparticles respectively. The average surface charge was measured to be +26.9 +/- 0.19 mV and +27.68 +/- 0.20 mV for Cy3-BHGCA and Cy3-BHGCA- BALN nanoparticles respectively. Binding affinity using hydroxyapatite (HA) revealed that both Cy3 BHGCA BALN and Cy3 BHGCA nanoparticles displayed 95% binding in 24 hours. However, the biotin quenched nanoparticle Cy3 BHGCAB displayed 68% binding in 24 hours. The synthesis and binding chemistry was verified using Fourier transform infrared spectroscopy (FTIR).

  4. Effects of nanometric hydrophobic layer on performances of solar photovoltaic collectors

    Directory of Open Access Journals (Sweden)

    Andrei BUTUZA

    2014-11-01

    Full Text Available The study refers to the experimental investigation of solar photovoltaic collectors' behaviour when the glazed surface is treated with a nanometric layer of hydrophobic solution. The experiment was carried out on two photovoltaic collectors, of which one was considered as reference and the other one was coated with a commercial hydrophobic solution. It was studied the evolution of the following electrical parameters: current, voltage, power, efficiency and daily energy production. The voltage was almost unaffected, but for all the others parameters, important drop were recorded. The preliminary conclusion of the study is that the use of hydrophobic solutions, for the treatment of glazed surfaces of solar collectors is not recommended. This hypothesis needs supplementary investigations and measurements in the context of reduced available information concerning the optical properties of hydrophobic solutions.

  5. Hydrophobicity studies of polymer thin films with varied CNT concentration

    Science.gov (United States)

    M. Rodzi, N. H.; M. Shahimin, M.; Poopalan, P.; Man, B.; M. Nor, M. N.

    2013-12-01

    Surface functionalization studies for re-creating a `Lotus Leaf' effect (superhydrophobic) have been carried out for the past decade; looking for the material which can provide high transparency, low energy surface and high surface roughness. Fabrication of polydimethylsiloxane (PDMS) and multiwalled carbon nanotubes (MWCNT) hybrid thin film variations on glass to produce near-superhydrophobic surfaces is presented in this paper. There are three important parameters studied in producing hydrophobic surfaces based on the hybrid thin films; concentration of PDMS, concentration of MWCNT and droplet sizes. The study is carried out by using PDMS of varied cross linker ratio (10:1, 30:1 and 50:1) with MWCNT concentration of 1mg, 10mg and 15mg for 0.5 μl, 2.0 μl, 5.0 μl and 10 μl droplet sizes. The resulting hybrid thin films show that hydrophobicity increased with increasing cross linker ratio and MWCNT percentage in the PDMS solution. A near superhydrophobic surface can be created when using 15 mg of MWCNT with 50:1 cross linker ratio PDMS thin films, measured on 10 μl droplet size. The hybrid thin films produced can be potentially tailored to the application of biosensors, MEMS and even commercial devices.

  6. Ligand binding induces a sharp decrease in hydrophobicity of folate binding protein assessed by 1-anilinonaphthalene-8-sulphonate which suppresses self-association of the hydrophobic apo-protein

    DEFF Research Database (Denmark)

    Holm, Jan; Lawaetz, Anders Juul; Hansen, Steen I.

    2012-01-01

    decrease of the surface hydrophobicity associated with the ligand-induced conformation change of FBP, and protein-inter-protein interactions involved in self-association of hydrophobic apo-FBP. The extrinsic fluorescent apolar dye 1-anilinonaphthalene-8-sulphonate (ANS) exhibited enhanced fluorescence...

  7. Stabilization of enzyme by using hydrophobic ligands

    Energy Technology Data Exchange (ETDEWEB)

    Ota, H.; Yamahara, K.; Kuboi, R. [Osaka University, Osaka (Japan)

    1998-02-01

    The protection (stabilization) effect of various hydrophobic ligands on the denaturation and aggregation of carbonic anhydrase from bovine (CAB) has been quantitatively investigated under various heat stress conditions. In a limited temperature range (40-60degC), where the protein was only partially denatured and the local hydrophobicities (LH) of CAB were positive effective stabilization of the protein is achieved by the addition of various ligands. The importance of balance between hydrophobic head and hydrophilic tail of the ligands is hypothesized. 18 refs., 5 figs.

  8. Hydrophobic Light-to-Heat Conversion Membranes with Self-Healing Ability for Interfacial Solar Heating

    KAUST Repository

    Zhang, Lianbin

    2015-07-01

    Self-healing hydrophobic light-to-heat conversion membranes for interfacial solar heating are fabricated by deposition of light-to-heat conversion material of polypyrrole onto porous stainless steel mesh, followed by hydrophobic fluoroalkylsilane modification. The mesh-based membranes spontaneously stay at the water–air interface, collect and convert solar light into heat, and locally heat only the water surface for an enhanced evaporation.

  9. Hydrophobic Light-to-Heat Conversion Membranes with Self-Healing Ability for Interfacial Solar Heating.

    Science.gov (United States)

    Zhang, Lianbin; Tang, Bo; Wu, Jinbo; Li, Renyuan; Wang, Peng

    2015-09-02

    Self-healing hydrophobic light-to-heat conversion membranes for interfacial solar heating are fabricated by deposition of light-to-heat conversion material of polypyrrole onto a porous stainless-steel mesh, followed by hydrophobic fluoroalkylsilane modification. The mesh-based membranes spontaneously stay at the water-air interface, collect and convert solar light into heat, and locally heat only the water surface for enhanced evaporation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Hydrophobicity study of kaolinite from La Unión, Antioquia

    Directory of Open Access Journals (Sweden)

    Liliana M. Usuga-Manco

    2015-07-01

    Full Text Available In this research three methodologies to convert the hydrophilic surface of kaolinite into a hydrophobic surface are proposed, this condition is required to recover this mineral by means of froth flotation. Taking into account the anisotropy, zeta potential and complex surface electrical properties of the kaolinite, three surface chemical treatments based on the interacting and absorption of anionic collectors onto the mineral surface, causing an increase in the contact angle and thus increased hydrophobicity of kaolinite were applied. The methodologies proposed were interactions of kaolinite particles with: sodium dodecyl sulfate solutions with concentration 1x10-3M, 1x10-4M, 1x10-5M; sodium dodecyl sulfate solutions 1x10-3M, 1x10-4M, 1x10-5M with further interaction with kerosene solutions 127000 ppm; and oleic acid solutions 1x10-3M, 1x10-4M, 1x10-5M, each one with a five minutes of interaction. The experimental results obtained by zeta potential and contact angle of the kaolinite before and after applying chemical treatments indicate that larger the chain length of the collector and its concentration, bigger the contact angle and so, more hydrophobic the surface (edge or face. In order to optimize, control and understand this solid-liquid interaction phenomenon is suggested to find out about the hydrophobization mechanism of kaolinite with oleic acid and its percentage of hydrophobization.

  11. Optically transparent super-hydrophobic thin film fabricated by reusable polyurethane-acrylate (PUA) mold

    Science.gov (United States)

    Park, J.-S.; Park, J.-H.; Lee, D.-W.

    2018-02-01

    In this paper, we describe a simple manufacturing method for producing an optically transparent super-hydrophobic polymer thin film using a reusable photo-curable polymer mold. Soluble photoresist (PR) molds were prepared with under-exposed and under-baked processes, which created unique hierarchical micro/nano structures. The reverse phase of the PR mold was replicated on the surface of polydimethylsiloxane (PDMS) substrates. The unique patterns on the replicated PDMS molds were successfully transferred back to the UV curable polyurethane-acrylate (PUA) using a laboratory-made UV exposure system. Continuous production of the super-hydrophobic PDMS thin film was demonstrated using the reusable PUA mold. In addition, hydrophobic nano-silica powder was sprayed onto the micro/nano structured PDMS surfaces to further improve hydrophobicity. The fabricated PDMS thin films with hierarchical surface texturing showed a water contact angle  ⩾150°. Excellent optical transmittance within the range of visible light of wavelengths between 400-800 nm was experimentally confirmed using a spectrophotometer. High efficiency of the super-hydrophobic PDMS film in optical transparency was also confirmed using solar panels. The fabricated PUA molds are very suitable for use in roll-to-roll or roll-to-plate systems which allow continuous production of super-hydrophobic thin films with an excellent optical transparency.

  12. Synthesis, Characterization and Application of Hydrophobic Zeolites

    OpenAIRE

    Heidari, Rulis

    2016-01-01

    The aim of the thesis was to design and synthesize a type of zeolite with the characteristics of hydrophobicity, high porosity, and proper pore size, which can be used for high-performance adsorption of ethanol from aqueous solution. In addition, the aim was to synthesize hydrophobic microporous zeolites including theoretic and experimental content. The experiment was carried out using hydroxide basic system and hydrogen fluoride neutral based on hydrothermal methods. Pure silica zeolites...

  13. Theoretical models regarding factors influencing switching regimes and the hydrological and erosional significance of hydrophobicity

    Science.gov (United States)

    Walsh, Rory; Urbanek, Emilia; Ferreira, Carla; Shakesby, Richard; Bento, Celia; Ferreira, Antonio

    2013-04-01

    The influence which soil hydrophobicity may have on hillslope hydrology and erosion in any location will depend on the proportion of storm events in which it is spatially contiguous. This in turn is dependent upon (a) the speed and three-dimensional pattern with which it disappears in wet weather and (b) the speed, three-dimensional pattern and degree of re-establishment of hydrophobicity in dry weather following hydrophilic or partially hydrophilic episodes. This paper draws upon results of laboratory and field investigations of changes through time in hydrophobicity, as well as recent advances in knowledge of switching mechanisms, to develop theory relating to hydrophobicity, its three-dimensional temporal dynamics and controls and its influence on overland flow and slopewash. Particular attention is given to modelling temporal change following fire. Use is made of key findings from (1) a field study of changes over a 4.2-year period January 2009 to March 2013 in hydrophobicity at two 10 m x 10 m grids (270 points, surface and 5 cm depth) on heather moorland in Central Portugal, where one grid was burned by an experimental fire in February 2009 and the other was an immediately adjacent unburned control; (2) a laboratory study of three-dimensional change in hydrophobicity with wetting (by an 8 mm simulated rainfall) and at different stages in an 80-hour drying phase of three different but initially equally hydrophobic soils, each of which comprising variants with and without artificial vertical routeways (simulated roots or linear cracks) and with or without drainage impedance at 2.5 cm depth. A series of theoretical models are presented addressing 1) factors and mechanisms influencing post-fire temporal change in hydrophobicity and (2) factors and mechanisms controlling the significance and temporal dynamics of hydrophobicity influence on overland flow and erosion (i) in unburned terrain and (ii) following fire. The field evidence from Portugal suggests a three

  14. Voltage Gating of a Biomimetic Nanopore: Electrowetting of a Hydrophobic Barrier.

    Science.gov (United States)

    Trick, Jemma L; Song, Chen; Wallace, E Jayne; Sansom, Mark S P

    2017-02-28

    It is desirable that nanopores that are components of biosensors are gated, i.e., capable of controllable switching between closed (impermeable) and open (permeable) states. A central hydrophobic barrier within a nanopore may act as a voltage-dependent gate via electrowetting, i.e., changes in nanopore surface wettability by application of an electric field. We use "computational electrophysiology" simulations to demonstrate and characterize electrowetting of a biomimetic nanopore containing a hydrophobic gate. We show that a hydrophobic gate in a model β-barrel nanopore can be functionally opened by electrowetting at voltages that do not electroporate lipid bilayers. During the process of electrowetting, voltage-induced alignment of water dipoles occurs within the hydrophobic gate region of the nanopore, with water entry preceding permeation of ions through the opened nanopore. When the ionic imbalance that generates a transbilayer potential is dissipated, water is expelled from the hydrophobic gate and the nanopore recloses. The open nanopore formed by electrowetting of a "featureless" β-barrel is anionic selective due to the transmembrane dipole potential resulting from binding of Na + ions to the headgroup regions of the surrounding lipid bilayer. Thus, hydrophobic barriers can provide voltage-dependent gates in designed biomimetic nanopores. This extends our understanding of hydrophobic gating in synthetic and biological nanopores, providing a framework for the design of functional nanopores with tailored gating functionality.

  15. Long-term clinical protection from falciparum malaria is strongly associated with IgG3 antibodies to merozoite surface protein 3.

    Directory of Open Access Journals (Sweden)

    Christian Roussilhon

    2007-11-01

    Full Text Available BACKGROUND: Surrogate markers of protective immunity to malaria in humans are needed to rationalize malaria vaccine discovery and development. In an effort to identify such markers, and thereby provide a clue to the complex equation malaria vaccine development is facing, we investigated the relationship between protection acquired through exposure in the field with naturally occurring immune responses (i.e., induced by the parasite to molecules that are considered as valuable vaccine candidates. METHODS AND FINDINGS: We analyzed, under comparative conditions, the antibody responses of each of six isotypes to five leading malaria vaccine candidates in relation to protection acquired by exposure to natural challenges in 217 of the 247 inhabitants of the African village of Dielmo, Senegal (96 children and 121 older adolescents and adults. The status of susceptibility or resistance to malaria was determined by active case detection performed daily by medical doctors over 6 y from a unique follow-up study of this village. Of the 30 immune responses measured, only one, antibodies of the IgG3 isotype directed to merozoite surface protein 3 (MSP3, was strongly associated with clinical protection against malaria in all age groups, i.e., independently of age. This immunological parameter had a higher statistical significance than the sickle cell trait, the strongest factor of protection known against Plasmodium falciparum. A single determination of antibody was significantly associated with the clinical outcome over six consecutive years in children submitted to massive natural parasite challenges by mosquitoes (over three parasite inoculations per week. Finally, the target epitopes of these antibodies were found to be fully conserved. CONCLUSIONS: Since anti-MSP3 IgG3 antibodies can naturally develop along with protection against P. falciparum infection in young children, our results provide the encouraging indication that these antibodies should be

  16. Highly efficient and large-scale fabrication of superhydrophobic alumina surface with strong stability based on self-congregated alumina nanowires.

    Science.gov (United States)

    Peng, Shan; Tian, Dong; Yang, Xiaojun; Deng, Wenli

    2014-04-09

    In this study, a large-area superhydrophobic alumina surface with a series of superior properties was fabricated via an economical, simple, and highly effective one-step anodization process, and subsequently modified with low-surface-energy film. The effects of the anodization parameters including electrochemical anodization time, current density, and electrolyte temperature on surface morphology and surface wettability were investigated in detail. The hierarchical alumina pyramids-on-pores (HAPOP) rough structure which was produced quickly through the one-step anodization process together with a low-surface-energy film deposition [1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDES) and stearic acid (STA)] confer excellent superhydrophobicity and an extremely low sliding angle. Both the PDES-modified superhydrophobic (PDES-MS) and the STA-modified superhydrophobic (STA-MS) surfaces present fascinating nonwetting and extremely slippery behaviors. The chemical stability and mechanical durability of the PDES-MS and STA-MS surfaces were evaluated and discussed. Compared with the STA-MS surface, the as-prepared PDES-MS surface possesses an amazing chemical stability which not only can repel cool liquids (water, HCl/NaOH solutions, around 25 °C), but also can show excellent resistance to a series of hot liquids (water, HCl/NaOH solutions, 30-100 °C) and hot beverages (coffee, milk, tea, 80 °C). Moreover, the PDES-MS surface also presents excellent stability toward immersion in various organic solvents, high temperature, and long time period. In particular, the PDES-MS surface achieves good mechanical durability which can withstand ultrasonication treatment, finger-touch, multiple fold, peeling by adhesive tape, and even abrasion test treatments without losing superhydrophobicity. The corrosion resistance and durability of the diverse-modified superhydrophobic surfaces were also examined. These fascinating performances makes the present method suitable for large

  17. Role of textile substrate hydrophobicity on the adsorption of hydrosoluble nonionic block copolymers.

    Science.gov (United States)

    Song, Junlong; Salas, Carlos; Rojas, Orlando J

    2015-09-15

    The adsorption of polyalkylene glycols and co-polymers of ethylene oxide and propylene oxide on substrates relevant to textiles with varying surface energies (cellulose, polypropylene, nylon and polyester) was studied by using quartz crystal microgravimetry. Langmuirian-type isotherms were observed for the adsorption profiles of nonionic block polymers of different architectures. The affinity with the surfaces is discussed based on experimental observations, which highlights the role of hydrophobic effects. For a given type of block polymer, micellar and monomeric adsorption is governed by the balance of polymer structure (mainly, chain length of hydrophobic segments) and substrate's surface energy. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Creation of a new eye lens crystallin (Gambeta) through structure-guided mutagenic grafting of the surface of betaB2 crystallin onto the hydrophobic core of gammaB crystallin.

    Science.gov (United States)

    Kapoor, Divya; Singh, Balvinder; Subramanian, Karthikeyan; Guptasarma, Purnananda

    2009-06-01

    The degree of conservation of three-dimensional folds in protein superfamilies is greater than that of amino acid sequences. Therefore, very different groups of residues (and schemes of residue packing) can be found displayed upon similar structural scaffolds. We have previously demonstrated the workability of a protein engineering-based method for rational mixing of the interior features of an all-beta enzyme with the substrate-binding and catalytic (surface) features of another enzyme whose sequence is not similar but which is structurally homologous to the first enzyme. Here, we extend this method to whole-protein surfaces and interiors. We show how two all-beta Greek key proteins, betaB2 crystallin and gammaB crystallin, can be recombined to produce a new protein through rational transplantation of the entire surface of betaB2 crystallin upon the structure of gammaB crystallin, without altering the latter's interior. This new protein, Gambeta, consists of 61 residues possessing the same identity at structurally equivalent positions in betaB2- and gammaB crystallin, 91 surface residues unique to betaB2 crystallin, and 27 interior residues unique to gammaB crystallin. Gambeta displays a mixture of the structural/biochemical characteristics, surface features and colligative properties of its progenitor crystallins. It also displays optical properties common to both progenitor crystallins (i.e. retention of transparency at high concentrations, as well as high refractivity). The folding of a protein with such a 'patchwork' residue ancestry suggests that interior/surface transplants involving all-beta proteins are a feasible engineering strategy.

  19. Fabricated super-hydrophobic film with potentiostatic electrolysis method on copper for corrosion protection

    International Nuclear Information System (INIS)

    Wang Peng; Qiu Ri; Zhang Dun; Lin Zhifeng; Hou Baorong

    2010-01-01

    A novel one-step potentiostatic electrolysis method was proposed to fabricate super-hydrophobic film on copper surface. The resulted film was characterized by contact angle tests, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FE-SEM) and electrochemical measurements. It could be inferred that the super-hydrophobic property resulted from the flower-like structure of copper tetradecanoate film. In the presence of super-hydrophobic film, the anodic and cathodic polarization current densities are reduced for more than five and four orders of magnitude, respectively. The air trapped in the film is the essential contributor of the anticorrosion property of film for its insulation, the copper tetradecanoate film itself acts as a 'frame' to trap air as well as a coating with inhibition effect. The super-hydrophobic film presents excellent inhibition effect to the copper corrosion and stability in water containing Cl - .

  20. Super-hydrophobic nickel films with micro-nano hierarchical structure prepared by electrodeposition

    International Nuclear Information System (INIS)

    Hang Tao; Hu Anmin; Ling Huiqin; Li Ming; Mao Dali

    2010-01-01

    Super-hydrophobic nickel films were prepared by a simple and low cost electrodepositing method. The surface morphologies of the films characterized by scanning electronic microscope exhibit hierarchical structure with micro-nanocones array, which can be responsible for their super-hydrophobic characteristic (water contact angle over 150 o ) without chemical modification. The wettability of the film can be varied from super-hydrophobic (water contact angle 154 o ) to relatively hydrophilic (water contact angle 87 o ) by controlling the size of the micro-nanocones. The mechanism of the hydrophobic characteristic of nickel films with this unique structure was illustrated by several models. Such micro-nanostructure and its special wettability are expected to be applied in the practical industry.

  1. Manufacturing of mushroom-shaped structures and its hydrophobic robustness analysis based on energy minimization approach

    Science.gov (United States)

    Wang, Li; Yang, Xiaonan; Wang, Quandai; Yang, Zhiqiang; Duan, Hui; Lu, Bingheng

    2017-07-01

    The construction of stable hydrophobic surfaces has increasingly gained attention owing to its wide range of potential applications. However, these surfaces may become wet and lose their slip effect owing to insufficient hydrophobic stability. Pillars with a mushroom-shaped tip are believed to enhance hydrophobicity stability. This work presents a facile method of manufacturing mushroom-shaped structures, where, compared with the previously used method, the modulation of the cap thickness, cap diameter, and stem height of the structures is more convenient. The effects of the development time on the cap diameter and overhanging angle are investigated and well-defined mushroom-shaped structures are demonstrated. The effect of the microstructure geometry on the contact state of a droplet is predicted by taking an energy minimization approach and is experimentally validated with nonvolatile ultraviolet-curable polymer with a low surface tension by inspecting the profiles of liquid-vapor interface deformation and tracking the trace of the receding contact line after exposure to ultraviolet light. Theoretical and experimental results show that, compared with regular pillar arrays having a vertical sidewall, the mushroom-like structures can effectively enhance hydrophobic stability. The proposed manufacturing method will be useful for fabricating robust hydrophobic surfaces in a cost-effective and convenient manner.

  2. Synthesis and characterization of lamellar aragonite with hydrophobic property

    International Nuclear Information System (INIS)

    Wang Chengyu; Xu Yang; Liu Yalan; Li Jian

    2009-01-01

    A novel and simple synthetic method for the preparation of hydrophobic lamellar aragonite has been developed. The crystallization of aragonite was conducted by the reaction of sodium carbonate with calcium chloride in the presence of sodium stearate. The resulting products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the contact angle. The results revealed that sodium stearate plays an important role in determining the structure and morphology of the sample. Besides, we have succeeded in surface modification of particles in situ at the same time. The contact angle of the modified aragonite reached 108.59 deg.

  3. Reversible superhydrophilicity and hydrophobicity switching of V2O5 thin films deposited by magnetron sputtering

    Science.gov (United States)

    Zhang, Chunzi; Peng, Zhiguang; Cui, Xiaoyu; Neil, Eric; Li, Yuanshi; Kasap, Safa; Yang, Qiaoqin

    2018-03-01

    V2O5 thin films are well-known "smart" materials due to their reversible wettability under UV irradiation and dark storage. Their surfaces are usually hydrophobic and turn into hydrophilic under UV irradiation. However, the V2O5 thin films deposited by magnetron sputtering in present work are superhydrophilic and turned into hydrophobic after days' of storage in air. This change can be recovered by heating. The effects of many factors including surface roughness, irradiation from visible light, UV, & X-ray, and storage in air & vacuum on the reversible switching of wettability were investigated. The results show that air absorption is the main factor causing the film surface change from superhydrophilicity to hydrophobicity.

  4. Controllable picoliter pipetting using hydrophobic microfluidic valves

    Science.gov (United States)

    Zhang, M.; Huang, J.; Qian, X.; Mi, S.; Wang, X.

    2017-06-01

    A picoliter pipetting technique using the microfluidic method is presented. Utilizing the hydrophobic self-assembled monolayer films patterned in microchannels as pressure-controlled valves, a small volume of liquid can be separated by a designed channel trap and then ejected from the channel end at a higher pressure. The liquid trap section is composed of a T-shaped channel junction and a hydrophobic patch. The liquid volume can be precisely controlled by varying the distance of the hydrophobic patch from the T-junction. By this means, liquid less than 100 pl can be separated and pipetted. The developed device is potentially useful for sample dispensing in biological, medical, and chemical applications.

  5. Enhanced water transport and salt rejection through hydrophobic zeolite pores

    Science.gov (United States)

    Humplik, Thomas; Lee, Jongho; O’Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N.

    2017-12-01

    The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

  6. Bio-inspired hydrophobic modification of cellulose nanocrystals with castor oil.

    Science.gov (United States)

    Shang, Qianqian; Liu, Chengguo; Hu, Yun; Jia, Puyou; Hu, Lihong; Zhou, Yonghong

    2018-07-01

    This work presents an efficient and environmentally friendly approach to generate hydrophobic cellulose nanocrystals (CNC) using thiol-containing castor oil (CO-SH) as a renewable hydrophobe with the assist of bio-inspired dopamine at room temperature. The modification process included the formation of the polydopamine (PDA) buffer layer on CNC surfaces and the Michael addition reaction between the catechol moieties of PDA coating and thiol groups of CO-SH. The morphology, crystalline structure, surface chemistry, thermal stability and hydrophobicity of the modified CNC were charactered by TEM, XRD, FT-IR, solid-state 13 C NMR, XPS, TGA and contact angle analysis. The modified CNC preserved cellulose crystallinity, displayed higher thermal stability than unmodified CNC, and was highly hydrophobic with a water contact angle of 95.6°. The simplicity and versatility of the surface modification strategy inspired by adhesive protein of mussel may promote rapid development of hydrophobic bio-based nanomaterials for various applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Hydrophobic and moisture-stable metal–organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Carlos A.; Nune, Satish K.; Annapureddy, Harsha V.; Dang, Liem X.; McGrail, B. Peter; Zheng, Feng; Polikarpov, Evgueni; King, David L.; Freeman, Charles J.; Brooks, Kriston P.

    2015-08-15

    Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO2 separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials (e.g., MgDOBDC and NiDOBDC) is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behavior and chemical stability against moisture without compromising CO2 sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. This allows MOF interaction/sorption of CO2 molecules comparable to unmodified MOFs. We herein report preliminary results on three routinely studied MOF materials [MIL-101(Cr), MgDOBDC and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO2 sorption capacity while reducing the water adsorption up to three times, respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF

  8. Influence of hydrophobization of fumed oxides on interactions with polar and nonpolar adsorbates

    Science.gov (United States)

    Gun'ko, V. M.; Pakhlov, E. M.; Goncharuk, O. V.; Andriyko, L. S.; Marynin, A. I.; Ukrainets, A. I.; Charmas, B.; Skubiszewska-Zięba, J.; Blitz, J. P.

    2017-11-01

    A variety of unmodified and modified fumed silica A-300 and silica/titania (ST20 and ST76 at 20 and 76 wt.% of titania, respectively) was prepared to analyze features of their interactions with polar and nonpolar adsorbates. The materials were studied using nitrogen adsorption-desorption, ethanol evaporation kinetics, infrared (IR) spectroscopy, thermogravimetry (TG), photon correlation spectroscopy, differential scanning calorimetry (DSC), DSC and TG thermoporometry, and quantum chemistry. Changes in surface structure of modified nanooxides with increasing hydrophobization degree (ΘMS) from 20% to 100% have a strong affect on the textural characteristics of the materials and adsorption-desorption of various adsorbates. Confined space effects enhanced due to the location of adsorbates in narrow voids between nanoparticles lead to freezing-melting point depression for bound polar and nonpolar adsorbates. The behavior of particles of modified nanooxides in aqueous and water/ethanol media is strongly altered due to enhanced aggregations with increasing value of ΘMS. All of these change are non-monotonic functions of ΘMS which affects (i) rearrangement of nanoparticles, (ii) interactions with polar and nonpolar adsorbates, (iii) location of adsorbates in voids of different sizes, (iv) the clustering of adsorbates and formation of nearly bulk structures.

  9. A study of degradation resistance and cytocompatibility of super-hydrophobic coating on magnesium.

    Science.gov (United States)

    Zhang, Yufen; Feyerabend, Frank; Tang, Shawei; Hu, Jin; Lu, Xiaopeng; Blawert, Carsten; Lin, Tiegui

    2017-09-01

    Calcium stearate based super-hydrophobic coating was deposited on plasma electrolytic oxidation (PEO) pre-treated magnesium substrate. The pre-treated magnesium and super-hydrophobic coating covered sample were characterized by scanning electron microscopy, X-ray diffraction and electrochemical corrosion measurements. The cytocompatibility and degradation resistance of magnesium, pre-treated magnesium and super-hydrophobic coating were analysed in terms of cell adhesion and osteoblast differentiation. The results indicate that the calcium stearate top coating shows super-hydrophobicity and that the surface is composed of micro/nanostructure. The super-hydrophobic coating covered sample shows higher barrier properties compared with the PEO pre-treated magnesium and bare magnesium. Human osteoblast proliferation, but not differentiation is enhanced by the PEO coating. Contrary, the super-hydrophobic coating reduces proliferation, but enhances differentiation of osteoblast, observable by the formation of hydroxyapatite. The combination of corrosion protection and cell reaction indicates that this system could be interesting for biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. In vitro evaluation of tissue adhesives composed of hydrophobically modified gelatins and disuccinimidyl tartrate

    Directory of Open Access Journals (Sweden)

    Miyuki Matsuda

    2012-01-01

    Full Text Available The effect of the hydrophobic group content in gelatin on the bonding strength of novel tissue–penetrating tissue adhesives was evaluated. The hydrophobic groups introduced into gelatin were the saturated hexanoyl, palmitoyl, and stearoyl groups, and the unsaturated oleoyl group. A collagen casing was employed as an adherend to model soft tissue for the in vitro determination of bonding strength of tissue adhesives composed of various hydrophobically modified gelatins and disuccinimidyl tartrate. The adhesive composed of stearoyl-modified gelatin (7.4% stearoyl; 10Ste and disuccinimidyl tartrate showed the highest bonding strength. The bonding strength of the adhesives decreased as the degree of substitution of the hydrophobic groups increased. Cell culture experiments demonstrated that fluorescein isothiocyanate-labeled 10Ste was integrated onto the surface of smooth muscle cells and showed no cytotoxicity. These results suggest that 10Ste interacted with the hydrophobic domains of collagen casings, such as hydrophobic amino acid residues and cell membranes. Therefore, 10Ste–disuccinimidyl tartrate is a promising adhesive for use in aortic dissection.

  11. Investigation of optical and microstructural properties of RF magnetron sputtered PTFE films for hydrophobic applications

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, S., E-mail: shilpatr3@gmail.com [Optics and Thin Film Laboratory, Bhabha Atomic Research Centre, Visakhapatnam (India); Haque, S. Maidul; Rao, K. Divakar; De, Rajnarayan [Optics and Thin Film Laboratory, Bhabha Atomic Research Centre, Visakhapatnam (India); Shripathi, T.; Deshpande, U.; Ganesan, V. [UGC-DAE Consortium for Scientific Research, Indore (India); Sahoo, N.K. [Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai (India)

    2016-11-01

    Highlights: • Polytetrafluoroethylene films were made by RF sputtering by varying deposition time. • With increasing deposition time, thickness shows unusual trend due to backsputtering. • Major contribution of CF{sub 2} and CF{sub 3} bonds in the samples is seen by ATR-FTIR. • Deposition time influences film thickness but all samples remain hydrophobic. • XPS spectra show strong CF{sub x} bonds at the surface. - Abstract: The deposition time dependence of optical, structural and morphological properties of thin as well as ultrathin Polytetrafluoroethylene (PTFE) sputtered films have been explored in the present communication. The films were prepared by RF magnetron sputtering under high vacuum condition, as a function of deposition time. The ellipsometry as well as X-ray reflectivity data show a drastic reduction in film thickness as the deposition time increases from 5 s to 10 s, possibly as a consequence of back sputtering. With subsequent deposition, back sputtering component decreases and hence, thickness increases with increase in deposition time. Atomic force microscopy (AFM) images show a slight change in growth morphology although roughness is independent of deposition time. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements showed the presence of C−C and CF{sub x} (x = 1–3) bonds in all the PTFE films. Supporting this, corresponding X-ray photoelectron spectroscopy (XPS) curves fitted for C-1s and F-1s peaks revealed a major contribution from CF{sub 2} bonds along with significant contribution from CF{sub 3} bonds leading to an F/C ratio of ∼1.5 giving hydrophobic nature of all the films.

  12. Investigation of optical and microstructural properties of RF magnetron sputtered PTFE films for hydrophobic applications

    International Nuclear Information System (INIS)

    Tripathi, S.; Haque, S. Maidul; Rao, K. Divakar; De, Rajnarayan; Shripathi, T.; Deshpande, U.; Ganesan, V.; Sahoo, N.K.

    2016-01-01

    Highlights: • Polytetrafluoroethylene films were made by RF sputtering by varying deposition time. • With increasing deposition time, thickness shows unusual trend due to backsputtering. • Major contribution of CF 2 and CF 3 bonds in the samples is seen by ATR-FTIR. • Deposition time influences film thickness but all samples remain hydrophobic. • XPS spectra show strong CF x bonds at the surface. - Abstract: The deposition time dependence of optical, structural and morphological properties of thin as well as ultrathin Polytetrafluoroethylene (PTFE) sputtered films have been explored in the present communication. The films were prepared by RF magnetron sputtering under high vacuum condition, as a function of deposition time. The ellipsometry as well as X-ray reflectivity data show a drastic reduction in film thickness as the deposition time increases from 5 s to 10 s, possibly as a consequence of back sputtering. With subsequent deposition, back sputtering component decreases and hence, thickness increases with increase in deposition time. Atomic force microscopy (AFM) images show a slight change in growth morphology although roughness is independent of deposition time. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements showed the presence of C−C and CF x (x = 1–3) bonds in all the PTFE films. Supporting this, corresponding X-ray photoelectron spectroscopy (XPS) curves fitted for C-1s and F-1s peaks revealed a major contribution from CF 2 bonds along with significant contribution from CF 3 bonds leading to an F/C ratio of ∼1.5 giving hydrophobic nature of all the films.

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

    Science.gov (United States)

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

    2008-05-01

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

  14. Molecular aggregation in water : the interplay of hydrophobic and electrostatic interactions

    NARCIS (Netherlands)

    Buwalda, Rixt Tietje

    2001-01-01

    Hydrophobic interactions belong to the most important noncovalent interactions and play an important role in many (bio)chemical processes. A number of processes in aqueous solution like protein folding, surfactant aggregation or molecular recognition processes strongly rely on the interactions

  15. Immobilization of molecular cobalt electrocatalyst by hydrophobic interaction with hematite photoanode for highly stable oxygen evolution

    KAUST Repository

    Joya, Khurram

    2015-07-15

    A unique modification of a hematite photoanode with perfluorinated Co-phthalocyanine (CoFPc) by strong binding associated with hydrophobic interaction is demonstrated. The resultant molecular electrocatalyst – hematite photoanode hybrid material showed significant onset shift and high stability for photoelectrochemical oxidation evolution reaction (OER).

  16. Mimicking the nanostructure of bamboo leaves (backside) for hydrophobicity using polydimethylsiloxane moulding and nano-imprint lithography.

    Science.gov (United States)

    Hwang, Jaeyeon; Hong, Sung-Hoon; Lee, Heon

    2009-06-01

    Extensive studies have revealed that various kinds of plant leaf have a hydrophobic property which arises from the micro- and nano-scale structure of the leaves. As the self-cleaning capability of plant leaves, termed the lotus effect, is based on their micro- and nano-scale structure, this hydrophobic property can be obtained on various other surfaces by duplication of the leaves' structure. In this study, the hydrophobic structure on bamboo leaves (Pseudosasa japonica) was successfully replicated on a glass substrate using polydimethylsiloxane (PDMS) molding technique and UV nano-imprint lithography. The replicated nano structure, made of perfluorinated acrylate imprint resin, was characterized by scanning electron microscopy (SEM) and its hydrophobicity was evaluated by contact angle measurements which confirmed that the hydrophobic nature and self-cleaning capability of the original bamboo leaves were also replicated.

  17. Hydrophobization of Concrete Using Granular Nanostructured Aggregate

    Science.gov (United States)

    Ogurtsova, Y. N.; Strokova, V. V.; Labuzova, M. V.

    2017-11-01

    The possibility of giving hydrophobical properties to the fine-grained concrete matrix by using a granular nanostructured aggregate (GNA) with a hydrophobizing additive is investigated in this work. GNA is obtained by granulating the silica raw material with an alkaline component. The introduction of a hydrophobizing additive into the raw mix of GNA allows to encapsulate it reducing the negative effect on hydration processes, the intensity of migration of moisture and efflorescence in concrete and, consequently, improving the performance characteristics of fine-grained concrete products. The hydrophobizing ability of a solution of sodium polysilicates formed in the core of GNA during concrete heat and moisture treatment is proved. The analysis of IR spectra after the impregnation of cement stone samples with a solution of sodium polysilicates showed an increase in the degree of hydration and the formation of framework water aluminosilicates. Atmospheric processes modelling showed that the use of GNA on the basis of gaize with calcium stearate and on the basis of fly ash with GKZh-11 makes it possible to increase the resistance of fine-grained concrete to the atmospheric effect of the medium, namely, the outwashing of readily soluble compounds.

  18. Hydrophobic interactions of phenoxazine modulators with bovine ...

    Indian Academy of Sciences (India)

    concentration of the drugs, higher numbers being obtained at higher drug concentrations. These results suggest that phenothiazine derivatives are bound by hydrophobic interaction to the aromatic amino acids of the BSA molecule and that, under the influence of high drug concentrations, the number of available sites ...

  19. hydrophobic silica membranes for gas separation

    NARCIS (Netherlands)

    de Vos, R.M.; Maier, Wilhelm F.; Verweij, H.

    1999-01-01

    The synthesis and properties of hydrophobic silica membranes are described. These membranes show very high gas permeance for small molecules, such as H2, CO2, N2, O2, and CH4, and permselectivities of 20–50 for these gases with respect to SF6 and larger alkanes like C3H8 and i-C4H10. The membranes

  20. Responsive gelation of hydrophobized linear polymer

    DEFF Research Database (Denmark)

    Madsen, Claus Greve; Toeth, Joachim; Jørgensen, Lene

    In this study we present the rheological properties of a physically linked polymer network, composed of linear hydrophilic chains, modified with hydrophobic moieties in each end. Solutions of the polymer in ethanol-water mixtures showed Newtonian behaviour up to about 99 % ethanol, with the highest...