scholarly journals Assembly of iron oxide nanosheets at the air–water interface by leucine–histidine peptides

RSC Advances ◽  
2021 ◽  
Vol 11 (45) ◽  
pp. 27965-27968
Author(s):  
Nina Hoinkis ◽  
Helmut Lutz ◽  
Hao Lu ◽  
Thaddeus W. Golbek ◽  
Mikkel Bregnhøj ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Water Interface ◽  
Wide Range ◽  
Air Water Interface ◽  
Inorganic Nanomaterials

The fabrication of inorganic nanomaterials is important for a wide range of disciplines.

scholarly journals Measurements of adsorption at the air-water interface by the microtome method

1936 ◽  
Vol 154 (883) ◽  
pp. 608-623 ◽  
Keyword(s):  
Dynamic Method ◽  
Fundamental Importance ◽  
Molecular Adsorption ◽  
Water Interface ◽  
Experimental Demonstration ◽  
Gibbs Equation ◽  
Experimental Conditions ◽  
Moving Surface ◽  
Wide Range ◽  
Air Water Interface

In spite of the wide use and fundamental importance of the classical Gibbs adsorption theorem, its validity has never been given adequate experimental demonstration. Until quite recently the principal means available for testing this theorem was the “moving bubble method”, developed by Donnan and Barker, and later by McBain, Davies, and DuBois. Almost without exception this method has given results many times greater than the values calculated from either the exact or the approximate Gibbs equation. A recent exhaustive investigation of this dynamic method by DuBois and Todd has shown, moreover, that the results for moving bubbles may be varied and controlled over a wide range by merely altering the size or speed of the bubbles or the amount of accompanying liquid. Thus the results, although definite and repro­ducible, vary greatly with the experimental conditions, and hence they bear no definite relation either to the Gibbs value or to that for mono-molecular adsorption. It is evident that a moving surface carries in general an amount of adsorbed material which is much greater than that predicted by the Gibbs theorem. Similar high results are reported by Seymour, Tartar, and Wright for moving droplets of benzene in water, which may carry with them as much soap as would correspond to twenty or more mono-layers.

Pressure fluctuations and interfacial robustness in turbulent flows over superhydrophobic surfaces

2015 ◽  
Vol 783 ◽  
pp. 448-473 ◽  
Author(s):  
J. Seo ◽  
R. García-Mayoral ◽  
A. Mani
Keyword(s):  
Drag Reduction ◽  
Numerical Simulations ◽  
Superhydrophobic Surface ◽  
Stagnation Pressure ◽  
Direct Numerical Simulations ◽  
Superhydrophobic Surfaces ◽  
Water Interface ◽  
System Parameters ◽  
Wide Range ◽  
Air Water Interface

Superhydrophobic surfaces can entrap gas pockets within their grooves when submerged in water. Such a mixed-phase boundary is shown to result in an effective slip velocity on the surface, and has promising potential for drag reduction and energy-saving in hydrodynamic applications. The target flow regime, in most such applications, is a turbulent flow. Previous analyses of this problem involved direct numerical simulations of turbulence with the superhydrophobic surface modelled as a flat boundary, but with a heterogeneous mix of slip and no-slip boundary conditions corresponding to the surface texture. Analysis of the kinematic data from these simulations has helped to establish the magnitude of drag reduction for various texture topologies. The present work is the first investigation that, alongside a kinematic investigation, addresses the robustness of superhydrophobic surfaces by studying the load fields obtain from data from direct numerical simulations (DNS). The key questions at the focus of this work are: does a superhydrophobic surface induce a different pressure field compared to a flat surface? If so, how does this difference scale with system parameters, and when does it become significant that it can deform the air–water interface and potentially rapture the entrapped gas pockets? To this end, we have performed DNS of turbulent channel flows subject to superhydrophobic surfaces over a wide range of texture sizes spanning values from $L^{+}=6$ to $L^{+}=155$ when expressed in terms of viscous units. The pressure statistics at the wall are decomposed into two contributions: one coherent, caused by the stagnation of slipping flow hitting solid posts, and one time-dependent, caused by overlying turbulence. The results show that the larger texture size intensifies the contribution of stagnation pressure, while the contribution from turbulence is essentially insensitive to $L^{+}$. The two-dimensional stagnation pressure distribution at the wall and the pressure statistics in the wall-normal direction are found to be self-similar for different $L^{+}$. The scaling of the induced pressure and the consequent deformations of the air–water interface are analysed. Based on our results, an upper bound on the texture wavelength is quantified that limits the range of robust operation of superhydrophobic surfaces when exposed to high-speed flows. Our results indicate that when the system parameters are expressed in terms of viscous units, the main parameters controlling the problem are $L^{+}$ and a Weber number based on inner dimensions; We obtain good collapse when all our results are expressed in wall units, independently of the Reynolds number.

scholarly journals Characterization of iron oxide nanoparticle films at the air–water interface in Arctic tundra waters

2018 ◽  
Vol 633 ◽  
pp. 1460-1468 ◽  
Author(s):  
Aaron M. Jubb ◽  
Jeremy R. Eskelsen ◽  
Xiangping Yin ◽  
Jianqiu Zheng ◽  
Michael J. Philben ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Arctic Tundra ◽  
Iron Oxide Nanoparticle ◽  
Water Interface ◽  
Nanoparticle Films ◽  
Air Water Interface ◽  
Oxide Nanoparticle

scholarly journals Eliminating effects of particle adsorption to the air/water interface in single-particle cryo-electron microscopy: Bacterial RNA polymerase and CHAPSO

2018 ◽  
Author(s):  
James Chen ◽  
Alex J. Noble ◽  
Jin Young Kang ◽  
Seth A. Darst
Keyword(s):  
Rna Polymerase ◽  
Single Particle ◽  
Particle Orientation ◽  
Water Interface ◽  
Bacterial Transcription ◽  
Ionic Detergent ◽  
Wide Range ◽  
Air Water Interface ◽  
Transcription Complexes ◽  
Orientation Bias

AbstractPreferred particle orientation presents a major challenge for many single particle cryoelectron microscopy (cryo-EM) samples. Orientation bias limits the angular information used to generate three-dimensional maps and thus affects the reliability and interpretability of the structural models. The primary cause of preferred orientation is presumed to be due to adsorption of the particles at the air/water interface during cryo-EM grid preparation. To ameliorate this problem, detergents are often added to cryo-EM samples to alter the properties of the air/water interface. We have found that many bacterial transcription complexes suffer severe orientation bias when examined by cryo-EM. The addition of non-ionic detergents, such as NP-40, does not remove the orientation bias but the Zwitter-ionic detergent CHAPSO significantly broadens the particle orientation distributions, yielding isotropically uniform maps. We used cryoelectron tomography to examine the particle distribution within the ice layer of cryo-EM grid preparations of Escherichia coli 6S RNA/RNA polymerase holoenzyme particles. In the absence of CHAPSO, essentially all of the particles are located at the ice surfaces. CHAPSO at the critical micelle concentration eliminates particle absorption at the air/water interface and allows particles to randomly orient in the vitreous ice layer. We find that CHAPSO eliminates orientation bias for a wide range of bacterial transcription complexes containing E. coli or Mycobacterium tuberculosis RNA polymerases. Findings of this study confirm the presumed basis for how detergents can help remove orientation bias in cryo-EM samples and establishes CHAPSO as a useful tool to facilitate cryo-EM studies of baterial transcription complexes.

Sampling and analysis of the air-water interface with SEM and EDS of microlayers

1989 ◽  
Vol 47 ◽  
pp. 1004-1005
Author(s):  
Randall W. Smith ◽  
John Dash
Keyword(s):  
Heavy Metals ◽  
Surface Microlayer ◽  
Surface Films ◽  
Water Interface ◽  
Physical Processes ◽  
Infrared Spectroscopic Analysis ◽  
Eds Analysis ◽  
Air Water Interface ◽  
Significant Area ◽  
Bulk Chemical

The structure of the air-water interface forms a boundary layer that involves biological ,chemical geological and physical processes in its formation. Freshwater and sea surface microlayers form at the air-water interface and include a diverse assemblage of organic matter, detritus, microorganisms, plankton and heavy metals. The sampling of microlayers and the examination of components is presently a significant area of study because of the input of anthropogenic materials and their accumulation at the air-water interface. The neustonic organisms present in this environment may be sensitive to the toxic components of these inputs. Hardy reports that over 20 different methods have been developed for sampling of microlayers, primarily for bulk chemical analysis. We report here the examination of microlayer films for the documentation of structure and composition.Baier and Gucinski reported the use of Langmuir-Blogett films obtained on germanium prisms for infrared spectroscopic analysis (IR-ATR) of components. The sampling of microlayers has been done by collecting fi1ms on glass plates and teflon drums, We found that microlayers could be collected on 11 mm glass cover slips by pulling a Langmuir-Blogett film from a surface microlayer. Comparative collections were made on methylcel1ulose filter pads. The films could be air-dried or preserved in Lugol's Iodine Several slicks or surface films were sampled in September, 1987 in Chesapeake Bay, Maryland and in August, 1988 in Sequim Bay, Washington, For glass coverslips the films were air-dried, mounted on SEM pegs, ringed with colloidal silver, and sputter coated with Au-Pd, The Langmuir-Blogett film technique maintained the structure of the microlayer intact for examination, SEM observation and EDS analysis were then used to determine organisms and relative concentrations of heavy metals, using a Link AN 10000 EDS system with an ISI SS40 SEM unit. Typical heavy microlayer films are shown in Figure 3.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

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