The Experts below are selected from a list of 286014 Experts worldwide ranked by ideXlab platform
Sylvie Roke - One of the best experts on this subject based on the ideXlab platform.
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The Jones-Ray Effect Is Not Caused by Surface-Active Impurities.
The journal of physical chemistry letters, 2018Co-Authors: Halil I. Okur, Eric Tyrode, Paul S. Cremer, Chad I. Drexler, Sylvie RokeAbstract:Pure aqueous electrolyte solutions display a minimum in surface tension at concentrations of 2 ± 1 mM. This Effect has been a source of controversy since it was first reported by Jones and Ray in t...
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The Jones-Ray Effect Is Not Caused by Surface Active Impurities
2018Co-Authors: Halil Okur, Chad Drexler, Eric Tyrode, Paul S. Cremer, Sylvie RokeAbstract:<p>Pure aqueous electrolyte solutions display a minimum in surface tension at concentrations of ~ 2 mM. This Effect has been a source of controversy since first reported by Jones and Ray in the 1930s. The Jones-Ray Effect and many other surface phenomena have frequently been dismissed as an artifact and linked to the presence of surface-active impurities. Herein we systematically consider the Effect of surface-active impurities by purposely adding nanomolar concentrations of surfactants to dilute electrolyte solutions. Trace amounts of surfactant are indeed found to decrease the surface tension and influence the surface chemistry. However, surfactants can be removed by repeated aspiration and stirring cycles, that eventually deplete the surfactant from solution creating a “surface chemically pure” interface. Upon following this cleaning procedure, a reduction in the surface tension of millimolar concentrations of salt is still observed. Consequently, we demonstrate the Jones-Ray Effect is not caused by surface active impurities. </p>
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The Jones-Ray Effect Reinterpreted: Surface Tension Minima of Low Ionic Strength Electrolyte Solutions are caused by Electric Field Induced Water-Water Correlations
Chemical Physics Letters, 2017Co-Authors: Halil I. Okur, Yixing Chen, David M. Wilkins, Sylvie RokeAbstract:Abstract The surface tension of electrolyte solutions exhibits a minimum at millimolar electrolyte concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray Effect, has been hotly debated over the past ∼80 years. If not considered as an artifact, it is typically ascribed to a phenomenological rare binding site for ions or ion pairs. Here, we propose an alternative underlying mechanism, namely that the hydrogen bond network of water responds to the collective electrostatic field of ions by increasing its orientational order, supported by recent surface tension measurements of NaCl solutions in H 2 O and D 2 O, and second harmonic scattering experiments in combination with ion resonant second harmonic reflection experiments. Recent thermodynamic and purely electrostatic treatments of the surface tension provide support for this interpretation. In addition, concerns related to possible artifacts influencing the measurements are quantified experimentally.
Richard J. Saykally - One of the best experts on this subject based on the ideXlab platform.
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strong surface adsorption of aqueous sodium nitrite as an ion pair
Chemical Physics Letters, 2012Co-Authors: Richard J. Saykally, Dale E Otten, Robert M Onorato, R Michaels, J GoodknightAbstract:Abstract We describe the first detailed experimental characterization of surface adsorption of an aqueous ion pair and quantify the unusual surface behavior of sodium nitrite, a ubiquitous component of natural waters. The onset of unusually strong adsorption at concentrations as low as ca. 0.1 M resembles the controversial ‘Jones–Ray Effect,’ wherein 13 salts exhibited surface tension minima in the millimolar region before resuming the normal linear increase with bulk concentrations. Given the compelling analogy recently found between adsorption of ions to the air–water interface, and the Hofmeister Effects of biochemistry, these results have important implications for the mechanism underlying these phenomena.
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Adsorption of ions to the surface of dilute electrolyte solutions: the Jones-Ray Effect revisited.
Journal of the American Chemical Society, 2005Co-Authors: Poul B. Petersen, Richard J. SaykallyAbstract:The controversial observation of a minimum in the surface tension of dilute aqueous electrolyte solutions by Jones and Ray in the 1930s is confirmed by new resonance-enhanced second harmonic generation (SHG) experiments demonstrating surface enhancement of simple inorganic anions in the same concentration range. New experiments show that the quadruply charged ferrocyanide, Fe(CN)64-, anion is not surface active at high concentrations, as expected, but at dilute concentrations, the anion is strongly attracted to the interface with a Gibbs free energy of adsorption of −6.8 kcal/mol. Using this value, the original Jones and Ray data are fit to a simple model of the surface tension with qualitative agreement, although better agreement is found for all 13 Jones and Ray salts with an even stronger surface adsorption.
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Direct experimental validation of the Jones-Ray Effect
Chemical Physics Letters, 2004Co-Authors: Poul B. Petersen, Justin C. Johnson, Kelly P. Knutsen, Richard J. SaykallyAbstract:In 1937, Jones and Ray observed a minimum in the surface tension of electrolyte solutions at � 1 mM concentrations. According to the Gibbs adsorption equation, a decreasing surface tension corresponds to an enhanced ion concentration at the interface, which is contrary to textbook descriptions based on Onsanger–Samaras theory. The Jones–Ray Effect has since been essentially dismissed as an artifact of the indirect experimental method used, and remains today as a curiosity. Here, we present direct experimental confirmation of the enhanced anion concentration around 1 mM of alkali iodide solutions using resonance enhanced femtosecond second harmonic generation, and the extraction of a large and negative value for the surface excess free energy (� 6.2 ± 0.2 kcal/mol). � 2004 Elsevier B.V. All rights reserved.
Halil I. Okur - One of the best experts on this subject based on the ideXlab platform.
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The Jones-Ray Effect Is Not Caused by Surface-Active Impurities.
The journal of physical chemistry letters, 2018Co-Authors: Halil I. Okur, Eric Tyrode, Paul S. Cremer, Chad I. Drexler, Sylvie RokeAbstract:Pure aqueous electrolyte solutions display a minimum in surface tension at concentrations of 2 ± 1 mM. This Effect has been a source of controversy since it was first reported by Jones and Ray in t...
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The Jones-Ray Effect Reinterpreted: Surface Tension Minima of Low Ionic Strength Electrolyte Solutions are caused by Electric Field Induced Water-Water Correlations
Chemical Physics Letters, 2017Co-Authors: Halil I. Okur, Yixing Chen, David M. Wilkins, Sylvie RokeAbstract:Abstract The surface tension of electrolyte solutions exhibits a minimum at millimolar electrolyte concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray Effect, has been hotly debated over the past ∼80 years. If not considered as an artifact, it is typically ascribed to a phenomenological rare binding site for ions or ion pairs. Here, we propose an alternative underlying mechanism, namely that the hydrogen bond network of water responds to the collective electrostatic field of ions by increasing its orientational order, supported by recent surface tension measurements of NaCl solutions in H 2 O and D 2 O, and second harmonic scattering experiments in combination with ion resonant second harmonic reflection experiments. Recent thermodynamic and purely electrostatic treatments of the surface tension provide support for this interpretation. In addition, concerns related to possible artifacts influencing the measurements are quantified experimentally.
Christopher J. Mundy - One of the best experts on this subject based on the ideXlab platform.
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Detecting the undetectable: The role of trace surfactant in the Jones-Ray Effect.
The Journal of chemical physics, 2018Co-Authors: Timothy Duignan, Marcel D. Baer, Mengsu Peng, Anh V. Nguyen, Xiu Song Zhao, Christopher J. MundyAbstract:The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray Effect refers to the observation that at extremely low salt concentration, the surface tension decreases. Determining the mechanism that is responsible for this Jones-Ray Effect is important for theoretically predicting the distribution of ions near surfaces. Here we use both experimental surface tension measurements and numerical solution of the Poisson-Boltzmann equation to demonstrate that very low concentrations of surfactant in water create a Jones-Ray Effect. We also demonstrate that the low concentrations of the surfactant necessary to create the Jones-Ray Effect are too small to be detectable by surface sensitive spectroscopic measurements. The Effect of surface curvature on this behavior is also examined, and the implications for unexplained bubble phenomena are discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.
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Surfactant Impurities Can Explain the Jones-Ray Effect
2018Co-Authors: Timothy Duignan, Marcel D. Baer, Christopher J. MundyAbstract:<div> <p> </p><div> <div> <div> <p>The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray Effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray Effect is important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray Effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this Effect. The Effect of surface curvature on this behavior is also examined and the implications for unexplained bubble phenomena is discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces. </p> </div> </div> </div> </div>
Roland R. Netz - One of the best experts on this subject based on the ideXlab platform.
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Charged Surface-Active Impurities at Nanomolar Concentration Induce Jones-Ray Effect.
The journal of physical chemistry letters, 2017Co-Authors: Yuki Uematsu, Douwe Jan Bonthuis, Roland R. NetzAbstract:The electrolyte surface tension exhibits a characteristic minimum around a salt concentration of 1 mM for all ion types, known as the Jones–Ray Effect. We show that a consistent description of the experimental surface tension of salts, bases, and acids is possible by assuming charged impurities in the water with a surface affinity typical for surfactants. Comparison with experimental data yields an impurity concentration in the nanomolar range, well below the typical experimental detection limit. Our modeling reveals salt-screening enhanced impurity adsorption as the mechanism behind the Jones–Ray Effect: for very low salt concentration added salt screens the electrostatic repulsion between impurities at the surface, which dramatically increases impurity adsorption and thereby reduces the surface tension.
