ORCID Profile
0000-0002-3956-6031
Current Organisations
University of Cagliari
,
Murdoch University
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Colloid and Surface Chemistry | Physical Chemistry (Incl. Structural)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in the Biological Sciences |
Publisher: American Chemical Society (ACS)
Date: 09-04-2019
Publisher: AIP Publishing
Date: 07-04-2015
DOI: 10.1063/1.4916519
Abstract: The relationship between surface charge and surface potential at the solid-liquid interface is often determined by a charge regulation process, the chemisorption of a potential determining ion such as H+. A subtle ion-specific effect can be observed when other ions compete with the primary potential determining ion to bind to a surface site. Site competition may involve alternative ions competing for a first binding site, e.g., metals ions competing with H+ to bind to a negatively charged oxide or carboxyl site. Second-binding sites with site competition may also be found, including hoteric OH2+ sites, or anion binding to amine groups. In this work, a general theoretical model is developed to describe the competitive adsorption of ions at surface sites. Applied to the calculation of forces, the theory predicts a 20% increase in repulsion between titania surfaces in 1 mM NaCl, and a 25% reduction in repulsion between silica surfaces in 0.1M NaCl compared to calculations neglecting ion site competition.
Publisher: American Physical Society (APS)
Date: 13-04-2001
Publisher: American Chemical Society (ACS)
Date: 11-07-2014
DOI: 10.1021/JP502887E
Abstract: Explaining and predicting the distribution of ions at the air-water interface has been a central challenge of physical chemistry for nearly a century. In essence, the problem amounts to calculating the change in the solvation energy of an ion as it approaches the interface. Here, we generalize our recently developed model of ionic solvation energies to calculate this interaction. The change in the Born energy as well as the static polarization response of the ion is included by using the conductor-like screening model (COSMO), which treats the ions quantum mechanically. Approximate expressions for the dispersion repulsion, cavity attraction, and surface potential contributions are also included. This model reproduces the surface tensions of electrolyte solutions and is consistent with ab initio molecular dynamics (MD) simulation. The model provides clear physical insight into iodide's adsorption. Unlike alternative models, no parameters are deliberately adjusted to reproduce surface tensions, and all of the important contributions to the interactions are included. Solving this problem has important direct implications for atmospheric chemistry and bubble properties. It also has important indirect implications for the more complex interactions of ions with protein and mineral surfaces. These play a fundamental role in a vast number of biological and industrial processes. The model is conceptually simple and has low computational demand, which facilitates its extension to these important applications.
Publisher: AIP Publishing
Date: 15-01-1998
DOI: 10.1063/1.475472
Abstract: A local continuum solvation theory, exactly treating electrostatic matching conditions on the boundary of a cavity occupied by a solute particle, is extended to cover time-dependent solvation phenomena. The corresponding integral equation is solved with a complex-valued frequency-dependent dielectric function ε(ω), resulting in a complex-valued ω-dependent reaction field. The inverse Fourier transform then produces the real-valued solvation energy, presented in the form of a time correlation function (TCF). We applied this technique to describe the solvation TCF for a benzophenone anion in Debye (acetonitrile) and two-mode Debye (dimethylformamide) solvents. For the Debye solvent the TCF is described by two exponential components, for the two-mode Debye solvent, by three. The overall dynamics in each case is longer than that given by the simple continuum model. We also consider a steady-state kinetic regime and the corresponding rate constant for adiabatic electron-transfer reactions. Here the boundary effect introduced within a frequency-dependent theory generates only a small effect in comparison with calculations made within the static continuum model.
Publisher: Public Library of Science (PLoS)
Date: 30-08-2013
Publisher: American Physical Society (APS)
Date: 14-06-2012
Publisher: Elsevier BV
Date: 12-2011
Publisher: American Chemical Society (ACS)
Date: 13-01-2009
DOI: 10.1021/JP802984B
Abstract: Ab initio molar volumes are calculated and used to derive radii for ions and neutral molecules using a spatially diffuse model of the electron distribution with Gaussian spread. The Gaussian radii obtained can be used for computation of nonelectrostatic ion-ion dispersion forces that underlie Hofmeister specific ion effects. Equivalent hard-sphere radii are also derived, and these are in reasonable agreement with crystalline ionic radii. The Born electrostatic self-energy is derived for a Gaussian model of the electronic charge distribution. It is shown that the ionic volumes used in electrostatic calculations of strongly hydrated cosmotropic ions ought best to include the first hydration shell. Ionic volumes for weakly hydrated chaotropic metal cations should exclude electron overlap (in electrostatic calculations). Spherical radii are calculated as well as nonisotropic ellipsoidal radii for nonspherical ions, via their nonisotropic static polarizability tensors.
Publisher: IEEE
Date: 04-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP00223J
Abstract: Buffer solutions do not simply regulate pH, but also change the properties of protein molecules.
Publisher: American Chemical Society (ACS)
Date: 27-08-2014
DOI: 10.1021/JP5081912
Publisher: Elsevier BV
Date: 2010
DOI: 10.1016/J.AAP.2009.07.019
Abstract: Dedicated short-range communication (DSRC) has been used in prototyped vehicles to test vehicle-to-vehicle communication for collision avoidance. However, there is little study on how collision avoidance software should behave to best mitigate accident collisions. In this paper, we analyse the timing of events and how they influence software-based collision avoidance strategies. We have found that the warning strategies for collision avoidance are constrained by the timing of events such as DSRC communication latency, detection range, road condition, driver reaction and deceleration rate. With these events, we define two collision avoidance timings: critical time to avoid collision and preferred time to avoid collision, and they dictate the design of software-based collision avoidance systems.
Publisher: Elsevier BV
Date: 06-2022
Publisher: ACM
Date: 17-10-2010
Publisher: Elsevier BV
Date: 05-2011
Publisher: IEEE
Date: 06-2011
Publisher: AIP Publishing
Date: 22-04-2014
DOI: 10.1063/1.4871412
Abstract: A method of incorporating surface roughness into theoretical calculations of surface forces is presented. The model contains two chief elements. First, surface roughness is represented as a probability distribution of surface heights around an average surface height. A roughness-averaged force is determined by taking an average of the classic flat-surface force, weighing all possible separation distances against the probability distributions of surface heights. Second the model adds a repulsive contact force due to the elastic contact of asperities. We derive a simple analytic expression for the contact force. The general impact of roughness is to lify the long range behaviour of noncontact (DLVO) forces. The impact of the elastic contact force is to provide a repulsive wall which is felt at a separation between surfaces that scales with the root-mean-square (RMS) roughness of the surfaces. The model therefore provides a means of distinguishing between “true zero,” where the separation between the average centres of each surface is zero, and “apparent zero,” defined by the onset of the repulsive contact wall. A normal distribution may be assumed for the surface probability distribution, characterised by the RMS roughness measured by atomic force microscopy (AFM). Alternatively the probability distribution may be defined by the histogram of heights measured by AFM. Both methods of treating surface roughness are compared against the classic smooth surface calculation and experimental AFM measurement.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CP06775H
Abstract: The dielectric properties of amorphous SiO 2 and other SiO 2 polymorphs are linked by simple volume dependence.
Publisher: Informa UK Limited
Date: 02-07-2016
Publisher: Elsevier BV
Date: 11-2002
Publisher: Elsevier BV
Date: 06-2011
Publisher: Elsevier BV
Date: 10-2022
DOI: 10.1016/J.COLSURFB.2022.112726
Abstract: Biointerfaces are significantly affected by electrolytes according to the Hofmeister series. This work reports a systematic investigation on the effect of different metal chlorides, sodium and potassium bromides, iodides and thiocyanates, on the ESI/MS spectra of bovine serum albumin (BSA) in aqueous solution at pH = 2.7. The concentration of each salt was varied to maximize the quality of the ESI/MS spectrum, in terms of peak intensity and bell-shaped profile. The ESI/MS spectra of BSA in the absence and in the presence of salts showed a main protein pattern characterized by the expected mass of 66.5 kDa, except the case of BSA/RbCl (mass 65.3 kDa). In all systems we observed an additional pattern, characterized by at least three peaks with low intensity, whose deconvolution led to suggest the formation of a BSA fragment with a mass of 19.2 kDa. Only NaCl increased the intensity of the peaks of the main BSA pattern, while minimizing that of the fragment. NaCl addition seems to play a crucial role in stabilizing the BSA ionized interface against hydrolysis of peptide bonds, through different synergistic mechanisms. To quantify the observed specific electrolyte effects, two "Hofmeister" parameters (H
Publisher: AIP Publishing
Date: 08-08-1999
DOI: 10.1063/1.479564
Publisher: American Chemical Society (ACS)
Date: 15-12-2017
Abstract: Theories for the effective polarizability of a small particle in a medium are presented using different levels of approximation: we consider the virtual cavity, real cavity, and the hard-sphere models as well as a continuous interpolation of the latter two. We present the respective hard-sphere and cavity radii as obtained from density-functional simulations as well as the resulting effective polarizabilities at discrete Matsubara frequencies. This enables us to account for macroscopic media in van der Waals interactions between molecules in water and their Casimir-Polder interaction with an interface.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SM01563A
Abstract: The electrostatic interaction between a patch of bilayer and the bare surface gives rise to the attraction between these hydrophobic surfaces.
Publisher: IEEE
Date: 04-2014
DOI: 10.1109/WICSA.2014.4
Publisher: Wiley
Date: 29-12-2019
Publisher: AIP Publishing
Date: 18-06-2012
DOI: 10.1063/1.4729822
Abstract: There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5–50 Å) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably, the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together.
Publisher: Elsevier BV
Date: 06-2014
Publisher: American Chemical Society (ACS)
Date: 09-06-2017
Abstract: The interaction between colloidal particles is commonly viewed through the lens of DLVO theory, whereby the interaction is described as the sum of the electrostatic and dispersion forces. For similar materials acting across a medium at pH values remote from the isoelectric point the theory typically involves an electrostatic repulsion that is overcome by dispersion forces at very small separations. However, the dominance of the dispersion forces at short separations is generally not seen in force measurements, with the exception of the interaction between mica surfaces. The discrepancy for silica surfaces has been attributed to hydration forces, but this does not explain the situation for titania surfaces where the dispersion forces are very much larger. Here, the interaction forces between very smooth hafnia surfaces have been measured using the colloid probe technique and the forces evaluated within the DLVO framework, including both hydration forces and the influence of roughness. The measured forces across a wide range of pH at different salt concentrations are well described with a single parameter for the surface roughness. These findings show that even small degrees of surface roughness significantly alter the form of the interaction force and therefore indicate that surface roughness needs to be included in the evaluation of surface forces between all surfaces that are not ideally smooth.
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier
Date: 2019
Publisher: Public Library of Science (PLoS)
Date: 29-05-2020
Publisher: Wiley
Date: 20-05-2016
DOI: 10.1002/SMR.1776
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2013
DOI: 10.1109/TSE.2012.74
Publisher: American Physical Society (APS)
Date: 02-02-2015
Publisher: Elsevier BV
Date: 07-2016
Publisher: American Chemical Society (ACS)
Date: 21-09-2009
DOI: 10.1021/LA902533X
Abstract: Ab initio quantum mechanical calculations of the dynamic polarizability of alkali metal and halide ions are performed as a function of imaginary frequency. Electron correlation is shown to provide a significant correction to ionic polarizabilities. Ab initio ion-surface dispersion coefficients are compared with single- and multimode London approximations. The commonly employed single-mode model with the characteristic frequency taken from the ionization potential of the ion is shown to be inadequate, underestimating dispersion forces with an average error around 40% or as high as 80% for halide ions. Decomposition of the polarizability data into five modes covers the major modes of each ion adequately (four modes for Li(+)). Illustrative calculations of surface potentials at the mica surface in aqueous alkali halide electrolytes are made. Charge reversal is obtained with the more polarizable cations, K(+) and Rb(+). The error in the single-mode ionization potential models is seen as a strong shift in the surface potential from negative toward positive values.
Publisher: ACM
Date: 05-09-2011
Publisher: Elsevier BV
Date: 06-2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP02797A
Abstract: Surface force measurements reveal that a small increase in surface charge enhance the long range hydrophobic attraction.
Publisher: Wiley
Date: 11-2022
Abstract: Early diagnosis of renal fibrosis is crucially significant on account of its worldwide prevalent tendency. Optical imaging in the near‐infrared window has been recognized as an appealing technique for the timely detection of renal dysfunction. However, formulating a contrast agent that allows early monitoring of renal fibrosis and concurrently renally clearable in a normal group is still challenging. Herein, a nanosized fluorophore with aggregation‐induced emission (AIE) features, namely AIE‐4PEG550 NPs, is well‐tailored and amenable to longitudinal visualization of the fibrosis progression specifically in the early‐stage via short‐wave infrared (SWIR, 900–1700 nm) fluorescence and photoacoustic bimodal imaging. The small size (≈26 nm), renally filtrable molecular weight (3.3 kDa), high renal clearance efficiency (93.1 ± 1.7% excretion through the kidneys within 24 h), outstanding imaging performance, and good biocompatibility, together make AIE‐4PEG550 NPs remarkably impressive and far superior to clinical diagnostic assays. The finding in this study would provide a blueprint for the next generation of diagnostic agents for the extent of renal fibrosis.
Publisher: IEEE
Date: 02-2017
Publisher: American Physical Society (APS)
Date: 30-11-2007
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP40150A
Abstract: Hofmeister series reversal can occur with change in pH, or increase in salt concentration. The phenomena are a challenge for any theory of ion specific effects. Recent theoretical work predicts how a complex interplay between ionic sizes, hydration and dispersion forces explains Hofmeister series reversal. Electrophoretic mobility measurements on lysozyme suspensions reported here are consistent with the theory.
Publisher: Elsevier BV
Date: 04-2015
Publisher: IEEE
Date: 05-2009
Publisher: Elsevier BV
Date: 2015
Publisher: KSI Research Inc. and Knowledge Systems Institute Graduate School
Date: 07-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9CP06836H
Abstract: Considering ice-premelting on a quartz rock surface ( i.e. silica) we calculate the Lifshitz excess pressures in a four layer system with rock–ice–water–air.
Publisher: IOP Publishing
Date: 02-2016
Publisher: Springer Berlin Heidelberg
Date: 2011
Publisher: American Physical Society (APS)
Date: 05-11-2015
Publisher: Springer International Publishing
Date: 2016
Publisher: American Chemical Society (ACS)
Date: 08-2013
DOI: 10.1021/JP403596C
Abstract: Physically accurate continuum solvent models that can calculate solvation energies are crucial to explain and predict the behavior of solute particles in water. Here, we present such a model applied to small spherical ions and neutral atoms. It improves upon a basic Born electrostatic model by including a standard cavity energy and adding a dispersion component, consistent with the Born electrostatic energy and using the same cavity size parameter. We show that the well-known, puzzling differences between the solvation energies of ions of the same size is attributable to the neglected dispersion contribution. This depends on dynamic polarizability as well as size. Generally, a large cancellation exists between the cavity and dispersion contributions. This explains the surprising success of the Born model. The model accurately reproduces the solvation energies of the alkali halide ions, as well as the silver(I) and copper(I) ions with an error of 12 kJ mol(-1) (±3%). The solvation energy of the noble gases is also reproduced with an error of 2.6 kJ mol(-1) (±30%). No arbitrary fitting parameters are needed to achieve this. This model significantly improves our understanding of ionic solvation and forms a solid basis for the investigation of other ion-specific effects using a continuum solvent model.
Publisher: IOP Publishing
Date: 06-2014
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2010
Publisher: Informa UK Limited
Date: 08-2013
DOI: 10.1080/08927014.2013.805209
Abstract: Vibrio spp. have the ability to form biofilms, which may contribute to the subsequent successful colonization by microfouling and macrofouling organisms. The effects of an antifouling compound, poly-ether B, on Vibrio sp. 010 were investigated using flow cytometry, proteomics, and metabolomics. A 2-D gel-based proteomic analysis was used to identify proteins responsive to poly-ether B treatment. The profiles of biofilm metabolites were analyzed by ultra-performance liquid chromatography-mass spectrometry. Poly-ether B caused a significant reduction in viability. The proteins affected by the treatment were related to nucleotide metabolism, the glyoxylate cycle, and stress responses. Metabolites such as tripeptides, fatty acids, and quorum-sensing molecules were regulated differentially. Down-regulation of proteins and metabolites potentially led to a loss in colonisation ability, thereby affecting the structure of the biofilm. These results suggest that the proteins and metabolites identified may serve as target molecules for potent antifouling compounds.
Publisher: ACM
Date: 24-05-2011
Publisher: Elsevier BV
Date: 07-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CP03349F
Abstract: Weak interactions are essential in modern research and technologies, such as nanocomposite materials, nanometer-sized quantum objects embedded in a host material or van der Waals heterostructures. Various fields address their characterisations and descriptions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP20538B
Abstract: The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloids, and corresponding theories of electrolytes, are unable to explain ion specific forces between colloidal particles quantitatively. The same is true generally, for surfactant aggregates, lipids, proteins, for zeta and membrane potentials and in adsorption phenomena. Even with fitting parameters the theory is not predictive. The classical theories of interactions begin with continuum solvent electrostatic (double layer) forces. Extensions to include surface hydration are taken care of with concepts like inner and outer Helmholtz planes, and "dressed" ion sizes. The opposing quantum mechanical attractive forces (variously termed van der Waals, Hamaker, Lifshitz, dispersion, nonelectrostatic forces) are treated separately from electrostatic forces. The ansatz that separates electrostatic and quantum forces can be shown to be thermodynamically inconsistent. Hofmeister or specific ion effects usually show up above ≈10(-2) molar salt. Parameters to accommodate these in terms of hydration and ion size had to be invoked, specific to each case. Ionic dispersion forces, between ions and solvent, for ion-ion and ion-surface interactions are not explicit in classical theories that use "effective" potentials. It can be shown that the missing ionic quantum fluctuation forces have a large role to play in specific ion effects, and in hydration. In a consistent predictive theory they have to be included at the same level as the nonlinear electrostatic forces that form the skeletal framework of standard theory. This poses a challenge. The challenges go further than academic theory and have implications for the interpretation and meaning of concepts like pH, buffers and membrane potentials, and for their experimental interpretation. In this article we overview recent quantitative developments in our evolving understanding of the theoretical origins of specific ion, or Hofmeister effects. These are demonstrated through an analysis that incorporates nonelectrostatic ion-surface and ion-ion dispersion interactions. This is based on ab initio ionic polarisabilities, and finite ion sizes quantified through recent ab initio work. We underline the central role of ionic polarisabilities and of ion size in the nonelectrostatic interactions that involve ions, solvent molecules and interfaces. Ex les of mechanisms through which they operate are discussed in detail. An ab initio hydration model that accounts for polarisabilities of the tightly held hydration shell of "cosmotropic" ions is introduced. It is shown how Hofmeister effects depend on an interplay between specific surface chemistry, surface charge density, pH, buffer, and counterion with polarisabilities and ion size. We also discuss how the most recent theories on surface hydration combined with hydrated nonelectrostatic potentials may predict experimental zeta potentials and hydration forces.
Publisher: American Chemical Society (ACS)
Date: 29-01-2010
DOI: 10.1021/LA9041265
Abstract: Surface potentials of alkali earth nitrates at a mica surface are calculated using a modified Poisson-Boltzmann approach that includes nonelectrostatic ion-surface dispersion interactions. New ab initio dynamic polarizabilities are used to determine dispersion interactions. A hydration model describing the hydration shell of cations is presented. Excellent agreement with experiment is achieved, including charge reversal at high electrolyte concentration without the need for site binding models. This suggests that specific ionic dispersion forces provide the mechanism for ion surface binding. An asymptotic surface potential is found in the limit of very high concentration. A Hofmeister series is predicted according to the strength of charge reversal, with Mg > Ca > Sr > Ba. The ion-surface dispersion adsorption energies of hydrated ions appear to explain the apparent repulsive secondary hydration forces observed experimentally between mica surfaces when taken with a surface hydration layer.
Publisher: American Chemical Society (ACS)
Date: 30-06-2011
DOI: 10.1021/LA202023R
Abstract: Protein solubility studies below the isoelectric point exhibit a direct Hofmeister series at high salt concentrations and an inverse Hofmeister series at low salt concentrations. The efficiencies of different anions measured by salt concentrations needed to effect precipitation at fixed cations are the usual Hofmeister series (Cl(-) > NO(3)(-) > Br(-) > ClO(4)(-) > I(-) > SCN(-)). The sequence is reversed at low concentrations. This has been known for over a century. Reversal of the Hofmeister series is not peculiar to proteins. Its origin poses a key test for any theoretical model. Such specific ion effects in the cloud points of lysozyme suspensions have recently been revisited. Here, a model for lysozymes is considered that takes into account forces acting on ions that are missing from classical theory. It is shown that both direct and reverse Hofmeister effects can be predicted quantitatively. The attractive/repulsive force between two protein molecules was calculated. To do this, a modification of Poisson-Boltzmann theory is used that accounts for the effects of ion polarizabilities and ion sizes obtained from ab initio calculations. At low salt concentrations, the adsorption of the more polarizable anions is enhanced by ion-surface dispersion interactions. The increased adsorption screens the protein surface charge, thus reducing the surface forces to give an inverse Hofmeister series. At high concentrations, enhanced adsorption of the more polarizable counterions (anions) leads to an effective reversal in surface charge. Consequently, an increase in co-ion (cations) adsorption occurs, resulting in an increase in surface forces. It will be demonstrated that among the different contributions determining the predicted specific ion effect the entropic term due to anions is the main responsible for the Hofmeister sequence at low salt concentrations. Conversely, the entropic term due to cations determines the Hofmeister sequence at high salt concentrations. This behavior is a remarkable ex le of the charge-reversal phenomenon.
Publisher: American Chemical Society (ACS)
Date: 08-2013
DOI: 10.1021/JP403595X
Abstract: The dispersion energy is an important contribution to the total solvation energies of ions and neutral molecules. Here, we present a new continuum model calculation of these energies, based on macroscopic quantum electrodynamics. The model uses the frequency dependent multipole polarizabilities of molecules in order to accurately calculate the dispersion interaction of a solute particle with surrounding water molecules. It includes the dipole, quadrupole, and octupole moment contributions. The water is modeled via a bulk dielectric susceptibility with a spherical cavity occupied by the solute. The model invokes d ing functions to account for solute-solvent wave function overlap. The assumptions made are very similar to those used in the Born model. This provides consistency and additivity of electrostatic and dispersion (quantum mechanical) interactions. The energy increases in magnitude with cation size, but decreases slightly with size for the highly polarizable anions. The higher order multipole moments are essential, making up more than 50% of the dispersion solvation energy of the fluoride ion. This method provides an accurate and simple way of calculating the notoriously problematic dispersion contribution to the solvation energy. The result establishes the importance of using accurate calculations of the dispersion energy for the modeling of solvation.
Publisher: Elsevier
Date: 2024
Publisher: IEEE
Date: 04-2016
DOI: 10.1109/QRASA.2016.8
Publisher: Elsevier BV
Date: 11-2010
Publisher: American Physical Society (APS)
Date: 11-01-2022
Publisher: Elsevier BV
Date: 11-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CP02822H
Abstract: We present a continuum solvent model of ion–ion interactions in water that reproduces activities with only two fitted parameters.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.JCIS.2014.01.018
Abstract: A new theoretical framework is now available to help explain ion specific (Hofmeister) effects. All measurements in physical chemistry show ion specificity, inexplicable by classical electrostatic theories. These ignore ionic dispersion forces that change ionic adsorption. We explored ion specificity in supercapacitors using a modified Poisson-Boltzmann approach that includes ionic dispersion energies. We have applied ab initio quantum chemical methods to determine required ion sizes and ion polarisabilities. Our model represents graphite electrodes through their optical dielectric spectra. The electrolyte was 1.2 M Li salt in propylene carbonate, using the common battery anions, PF6(-), BF4(-) and ClO4(-). We also investigated the perhalate series with BrO4(-) and IO4(-). The capacitance C=dσ/dψ was calculated from the predicted electrode surface charge σ of each electrode with potential ψ between electrodes. Compared to the purely electrostatic calculation, the capacitance of a positively charged graphite electrode was enhanced by more than 15%, with PF6(-) showing >50% increase in capacitance. IO4(-) provided minimal enhancement. The enhancement is due to adsorption of both anions and cations, driven by ionic dispersion forces. The Hofmeister series in the single-electrode capacitance was PF6(-)>BF4(-)>ClO4(-)>BrO4(-)>IO4(-) . When the graphite electrode was negatively charged, the perhalates provided almost no enhancement of capacitance, while PF6(-) and BF4(-) decreased capacitance by about 15%. Due to the asymmetric impact of nonelectrostatic ion interactions, the capacitances of positive and negative electrodes are not equal. The capacitance of a supercapacitor should therefore be reported as two values rather than one, similar to the matrix of mutual capacitances used in multielectrode devices.
Publisher: Wiley
Date: 07-07-2019
DOI: 10.1111/GGR.12278
Publisher: IOP Publishing
Date: 26-02-2015
Publisher: Elsevier BV
Date: 03-2010
Publisher: IEEE
Date: 04-2017
DOI: 10.1109/ICSA.2017.15
Publisher: American Chemical Society (ACS)
Date: 13-02-2018
DOI: 10.1021/ACS.LANGMUIR.7B03116
Abstract: The interactions between colloidal particles and nanoparticles determine solution stability and the structures formed when the particles are unstable to flocculation. Therefore, knowledge of the interparticle interactions is important for understanding the transport, dissolution, and fate of particles in the environment. The interactions between particles are governed by the surface properties of the particles, which are altered when species adsorb to the surface. The important interactions in the environment are almost never those between the bare particles but rather those between particles that have been modified by the adsorption of natural organic materials. Citric acid is important in this regard not only because it is present in soil but also as a model of humic and fulvic acids. Here we have studied the surface forces between the model metal oxide surface hafnia in the presence of citric acid in order to understand the stability of colloidal particles and nanoparticles. We find that citric acid stabilizes the particles over a wide range of pH at low to moderate ionic strength. At high ionic strength, colloidal particles will flocculate due to a secondary minimum, resulting in aggregates that are dense and easily redispersed. In contrast, nanoparticles stabilized by citric acid remain stable at high ionic strengths and therefore exist in solution as in idual particles this will contribute to their dispersion in the environment and the uptake of nanoparticles by mammalian cells.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP03165K
Abstract: The microscopic behaviour of neutral and dissolved particles near the boundary interface has been investigated. Depending on the applied excess polarisability model the results change dramatically from attraction to repulsion.
Publisher: EDP Sciences
Date: 06-2021
DOI: 10.1051/0004-6361/202040181
Abstract: Context. Gas hydrates can be stabilised outside their window of thermodynamic stability by the formation of an ice layer – a phenomenon termed self-preservation. This can lead to a positive buoyancy for clathrate particles containing CO 2 that would otherwise sink in the oceans of Enceladus, Pluto, and similar oceanic worlds. Aims. Here we investigate the implications of Lifshitz forces and low occupancy surface regions on type I clathrate structures for their self-preservation through ice layer formation, presenting a plausible model based on multi-layer interactions through dispersion forces. Methods. We used optical data and theoretical models for the dielectric response for water, ice, and gas hydrates with a different occupancy. Taking this together with the thermodynamic Lifshitz free energy, we modelled the energy minima essential for the formation of ice layers at the interface between gas hydrate and liquid water. Results. We predict the growth of an ice layer between 0.01 and 0.2 μm thick on CO, CH 4 , and CO 2 hydrate surfaces, depending on the presence of surface regions depleted in gas molecules. Effective hydrate particle density is estimated, delimiting a range of particle size and compositions that would be buoyant in different oceans. Over geological time, the deposition of floating hydrate particles could result in the accumulation of kilometre-thick gas hydrate layers above liquid water reservoirs and below the water ice crusts of their respective ocean worlds. On Enceladus, the destabilisation of near-surface hydrate deposits could lead to increased gas pressures that both drive plumes and entrain stabilised hydrate particles. Furthermore, on ocean worlds, such as Enceladus and particularly Pluto, the accumulation of thick CO 2 or mixed gas hydrate deposits could insulate its ocean against freezing. In preventing freezing of liquid water reservoirs in ocean worlds, the presence of CO 2 -containing hydrate layers could enhance the habitability of ocean worlds in our Solar System and on the exoplanets and exomoons beyond.
Publisher: Chapman and Hall/CRC
Date: 10-09-2013
DOI: 10.1201/B15530
Publisher: ACM
Date: 24-05-2011
Publisher: MDPI AG
Date: 12-05-2022
DOI: 10.3390/IJMS23105422
Abstract: Aurivillius oxides ferroelectric layered materials are formed by bismuth oxide and pseu-do-perovskite layers. They have a good ionic conductivity, which is beneficial for various photo-catalyzed reactions. Here, we synthesized ultra-thin nanosheets of two different Aurivillius oxides, Bi2WO6 (BWO) and Bi2MoO6 (BMO), by using a hard-template process. All materials were characterized through XRD, TEM, FTIR, TGA/DSC, DLS/ELS, DRS, UV-Vis. Band gap material (Eg) and potential of the valence band (EVB) were calculated for BWO and BMO. In contrast to previous reports on the use of multi composite materials, a new procedure for photocatalytic efficient BMO nanosheets was developed. The procedure, with an additional step only, avoids the use of composite materials, improves crystal structure, and strongly reduces impurities. BWO and BMO were used as photocatalysts for the degradation of the water pollutant dye malachite green (MG). MG removal kinetics was fitted with Langmuir—Hinshelwood model obtaining a kinetic constant k = 7.81 × 10−2 min−1 for BWO and k = 9.27 × 10−2 min−1 for BMO. Photocatalytic dye degradation was highly effective, reaching 89% and 91% MG removal for BWO and BMO, respectively. A control experiment, carried out in the absence of light, allowed to quantify the contribution of adsorption to MG removal process. Adsorption contributed to MG removal by a 51% for BWO and only by a 19% for BMO, suggesting a different degradation mechanism for the two photocatalysts. The advanced MG degradation process due to BMO is likely caused by the high crystallinity of the material synthetized with the new procedure. Reuse tests demonstrated that both photocatalysts are highly active and stable reaching a MG removal up to 95% at the 10th reaction cycle. These results demonstrate that BMO nanosheets, synthesized with an easy additional step, achieved the best degradation performance, and can be successfully used for environmental remediation applications.
Publisher: Substantia
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 04-09-2015
DOI: 10.1038/SREP13561
Abstract: The polychaetous annelid Neanthes acuminata complex has a widespread distribution, with the California population referred to as N. arenaceodentata . The reproductive pattern in this complex is unique, in that the female reproduces once and then dies, whereas the male can reproduce up to nine times. The male incubates the embryos until the larvae leave the male’s tube 21–28 days later and commences feeding. Reproductive success and protein expression patterns were measured over the nine reproductive periods. The percent success of the male in producing juveniles increased during the first three reproductive periods and then decreased, but the number of juveniles produced was similar through all nine periods. iTRAQ based quantitative proteomics were used to analyze the dynamics of protein expression patterns. The expression patterns of several proteins were found to be altered. The abundant expression of muscular and contractile proteins may have affected body weight and reproductive success. Sperm have never been observed fertilization occurs within the parent’s tube. Proteins associated with sperm maturation and fertilization were identified, including ATPase, clathrin, peroxiredoxins and enolase, which may provide clues to the molecular mechanisms enabling males to reproduce multiple times.
Publisher: Elsevier BV
Date: 09-2021
Publisher: AIP Publishing
Date: 06-1998
DOI: 10.1063/1.476357
Abstract: An algorithm is developed for performing calculations for the nonlocal electrostatic solvation theory of an ion in a cavity, accounting for electrostatic boundary conditions. The latter implies an induced charge distribution on the cavity surface as well as an induced volume charge distribution in the medium. This approach is validated by a variational derivation which also provides a general expression for the solvation energy. The procedure, implemented for spherical ions, is tested by calculating the analytic solution for an exponential nonlocal dielectric kernel and determining the corresponding solvation energy. Parametrization is presented for a range of solvents, fitted to experimental solvation energies. © 1998 American Institute of Physics.
Publisher: IEEE
Date: 09-2009
Publisher: Elsevier BV
Date: 08-2015
Publisher: AIP Publishing
Date: 06-1998
DOI: 10.1063/1.476358
Abstract: A nonlocal continuum theory of solvation is applied using an oscillating dielectric function with spatial dispersion. It is found that a convergent solution cannot be calculated using a model of a fixed solute cavity inside the solvent continuum. This is attributed to the fact that the dielectric oscillations appear as a result of coupling between polarization and density fluctuations, contradicting the concept of a fixed cavity. The theory is corrected by allowing the cavity size to vary. A cavitation energy and an interaction between the medium reaction field and the cavity size are added to the solvation free energy, and a new theory obtained by a variational treatment. The interaction term enables convergent solutions to become attainable, resulting in an oscillating electrostatic solvation energy as a function of cavity radius, the cavitation term enables these oscillations to be smoothed out, resulting in a regular, monotonic solvation free energy.
Publisher: ACM
Date: 14-05-2016
Publisher: IEEE
Date: 05-2015
Publisher: American Chemical Society (ACS)
Date: 25-03-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2015
Publisher: American Physical Society (APS)
Date: 27-12-2019
Publisher: American Chemical Society (ACS)
Date: 06-08-2013
DOI: 10.1021/JP404086U
Publisher: The Royal Society
Date: 16-06-2017
Abstract: A theoretical model of haemoglobin is presented to explain an anomalous cationic Hofmeister effect observed in protein aggregation. The model quantifies competing proposed mechanisms of non-electrostatic physisorption and chemisorption. Non-electrostatic physisorption is stronger for larger, more polarizable ions with a Hofmeister series Li + K + Cs + . Chemisorption at carboxylate groups is stronger for smaller kosmotropic ions, with the reverse series Li + K + Cs + . We assess aggregation using second virial coefficients calculated from theoretical protein–protein interaction energies. Taking Cs + to not chemisorb, comparison with experiment yields mildly repulsive cation–carboxylate binding energies of 0.48 k B T for Li + and 3.0 k B T for K + . Aggregation behaviour is predominantly controlled by short-range protein interactions. Overall, adsorption of the K + ion in the middle of the Hofmeister series is stronger than ions at either extreme since it includes contributions from both physisorption and chemisorption. This results in stronger attractive forces and greater aggregation with K + , leading to the non-conventional Hofmeister series K + Cs + ≈ Li + .
Publisher: American Chemical Society (ACS)
Date: 12-2018
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.JINORGBIO.2022.111872
Abstract: We examine Hofmeister specific ion effects of electrolytes added to protein solution under conditions minimizing electrostatic attraction between cations and positively charged protein. Hemoglobin (Hb) in aqueous solution at the denaturing pH = 2.7 is investigated in the presence of several metal chlorides, along with sodium and potassium bromides, iodides and thiocyanates, using electrospray ionization mass spectrometry (ESI-MS). Salt concentration was varied to maximize peak intensity and bell-shaped profile in the ESI-MS spectrum. The α-chain of myoglobin is identified as the main pattern of the ESI-MS spectra in all Hb-salt systems. Both peak intensity and quality of the bell-shaped profile of the protein spectrum decrease in the cation order: K
Publisher: American Chemical Society (ACS)
Date: 28-07-2020
Publisher: American Chemical Society (ACS)
Date: 27-03-2012
DOI: 10.1021/JP212154C
Publisher: AIP Publishing
Date: 15-07-2013
DOI: 10.1063/1.4813451
Publisher: Elsevier BV
Date: 10-2014
Publisher: IOP Publishing
Date: 02-2013
Publisher: American Physical Society (APS)
Date: 18-09-2014
Publisher: Georg Thieme Verlag KG
Date: 28-07-2022
DOI: 10.1055/A-1912-1096
Abstract: A general strategy for the synthesis of 2-substituted cyclobutanone sulfides via a tandem Brønsted acid-catalyzed nucleophile addition/ring contraction/C3-C4 ring expansion reaction sequence has been exploited. The procedure led to a wide panel of four-membered cyclic ketones in good to excellent yields and with broad substrate scope. Mechanistic aspects and kinetic parameters were investigated by quantum chemical DFT calculations, allowing us to rationalize the different reactivity of 2-aryl- and 2-alkyl-substituted 2-hydroxycyclobutanones towards thiol nucleophiles in reactions mediated by sulfonic acids. NMR and in situ Raman techniques were employed to better understand the reaction kinetics and parameters that affect the desired outcome.
Publisher: IEEE
Date: 08-2012
DOI: 10.1109/QSIC.2012.5
Publisher: American Chemical Society (ACS)
Date: 05-03-2014
DOI: 10.1021/JP410956M
Abstract: Continuum solvent models of electrolyte solutions are extremely useful. However, before we can use them with confidence, it is important to test them by comparison with a range of experimental properties. Here, we have adapted our recently developed1,2 simple continuum solvent model of ionic solvation free energies to calculate the solvation entropies and partial molar volumes of a group of monovalent and monatomic ions. This procedure gives good quantitative agreement for larger ions, and reproduces key qualitative features, such as the shift to positive entropies of solvation for iodide and the shift to negative partial molar volumes for small cations. Small ions require a correction to account for dielectric saturation effects, which brings them also into good agreement with experiment. We argue that this model does not require ad hoc corrections, and uses parameters that have good external physical justification. This work therefore establishes that our continuum solvent model can provide a satisfactory understanding of ionic solvation. It can thus serve as a foundation for improved models that explain and predict more complex ion specific effects.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2012
DOI: 10.1109/MS.2011.130
Publisher: American Physical Society (APS)
Date: 19-03-2018
Publisher: Elsevier BV
Date: 05-2022
Publisher: Springer International Publishing
Date: 2015
Publisher: SPIE
Date: 21-12-2007
DOI: 10.1117/12.759267
Publisher: CRC Press
Date: 03-09-2016
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 09-2022
Publisher: IEEE
Date: 08-2011
Publisher: Elsevier BV
Date: 02-2016
Publisher: World Scientific Pub Co Pte Lt
Date: 11-2015
DOI: 10.1142/S0218194015400367
Abstract: The causes of architecture changes can tell about why architecture changes, and this knowledge can be captured to prevent architecture knowledge vaporization and architecture degeneration. But the causes are not always known, especially in open source software (OSS) development. This makes it very hard to understand the underlying reasons for the architecture changes and design appropriate modifications. Architecture information is communicated in development mailing lists of OSS projects. To explore the possibility of identifying and understanding the causes of architecture changes, we conducted an empirical study to analyze architecture information (i.e. architectural threads) communicated in the development mailing lists of two popular OSS projects: Hibernate and ArgoUML, verified architecture changes with source code, and identified the causes of architecture changes from the communicated architecture information. The main findings of this study are: (1) architecture information communicated in OSS mailing lists does lead to architecture changes in code (2) the major cause for architecture changes in both Hibernate and ArgoUML is preventative changes, and the causes of architecture changes are further classified to functional requirement, external quality requirement, and internal quality requirement using the coding techniques of grounded theory (3) more than 45% of architecture changes in both projects happened before the first stable version was released.
Publisher: Wiley
Date: 17-03-2016
DOI: 10.1111/GCB.13249
Abstract: The metamorphosis of planktonic larvae of the Pacific oyster (Crassostrea gigas) underpins their complex life-history strategy by switching on the molecular machinery required for sessile life and building calcite shells. Metamorphosis becomes a survival bottleneck, which will be pressured by different anthropogenically induced climate change-related variables. Therefore, it is important to understand how metamorphosing larvae interact with emerging climate change stressors. To predict how larvae might be affected in a future ocean, we examined changes in the proteome of metamorphosing larvae under multiple stressors: decreased pH (pH 7.4), increased temperature (30 °C), and reduced salinity (15 psu). Quantitative protein expression profiling using iTRAQ-LC-MS/MS identified more than 1300 proteins. Decreased pH had a negative effect on metamorphosis by down-regulating several proteins involved in energy production, metabolism, and protein synthesis. However, warming switched on these down-regulated pathways at pH 7.4. Under multiple stressors, cell signaling, energy production, growth, and developmental pathways were up-regulated, although metamorphosis was still reduced. Despite the lack of lethal effects, significant physiological responses to both in idual and interacting climate change related stressors were observed at proteome level. The metamorphosing larvae of the C. gigas population in the Yellow Sea appear to have adequate phenotypic plasticity at the proteome level to survive in future coastal oceans, but with developmental and physiological costs.
Publisher: IEEE
Date: 08-2014
Publisher: IEEE
Date: 06-2011
Publisher: Elsevier BV
Date: 12-2012
Publisher: Elsevier BV
Date: 2020
Publisher: IGI Global
Date: 2012
Publisher: American Chemical Society (ACS)
Date: 14-05-2009
DOI: 10.1021/JP809051J
Abstract: In two-phase finite volume systems of electroneutral phospholipids, the electrolyte concentration is different in the two phases. The partitioning is highly anion-specific, a phenomenon not accounted for by classical electrolyte theories. It is explained if ionic dispersion forces that lead to specific ion binding are taken into account. The mechanism provides a contribution to active ion pumps not previously considered.
Publisher: AIP Publishing
Date: 13-06-2006
DOI: 10.1063/1.2209684
Abstract: The Wang-Landau Monte Carlo approach is applied to the coil-globule and melting transitions of off-lattice flexible homopolymers. The solid-liquid melting point and coil-globule transition temperatures are identified by their respective peaks in the heat capacity as a function of temperature. The melting and theta points are well separated, indicating that the coil-globule transition occurs separately from melting even in the thermodynamic limit. We also observe a feature in the heat capacity between the coil-globule and melting transitions which we attribute to a transformation from a low-density liquid globule to a high-density liquid globule.
Publisher: Elsevier BV
Date: 06-2016
Publisher: Cambridge University Press
Date: 04-2010
Publisher: American Chemical Society (ACS)
Date: 29-01-2013
DOI: 10.1021/PR3010088
Abstract: Larval growth of the polychaete worm Pseudopolydora vexillosa involves the formation of segment-specific structures. When larvae attain competency to settle, they discard swimming chaetae and secrete mucus. The larvae build tubes around themselves and metamorphose into benthic juveniles. Understanding the molecular processes, which regulate this complex and unique transition, remains a major challenge because of the limited molecular information available. To improve this situation, we conducted high-throughput RNA sequencing and quantitative proteome analysis of the larval stages of P. vexillosa. Based on gene ontology (GO) analysis, transcripts related to cellular and metabolic processes, binding, and catalytic activities were highly represented during larval-adult transition. Mitogen-activated protein kinase (MAPK), calcium-signaling, Wnt/β-catenin, and notch signaling metabolic pathways were enriched in transcriptome data. Quantitative proteomics identified 107 differentially expressed proteins in three distinct larval stages. Fourteen and 53 proteins exhibited specific differential expression during competency and metamorphosis, respectively. Dramatic up-regulation of proteins involved in signaling, metabolism, and cytoskeleton functions were found during the larval-juvenile transition. Several proteins involved in cell signaling, cytoskeleton and metabolism were up-regulated, whereas proteins related to transcription and oxidative phosphorylation were down-regulated during competency. The integration of high-throughput RNA sequencing and quantitative proteomics allowed a global scale analysis of larval transcripts roteins associated molecular processes in the metamorphosis of polychaete worms. Further, transcriptomic and proteomic insights provide a new direction to understand the fundamental mechanisms that regulate larval metamorphosis in polychaetes.
Publisher: American Chemical Society (ACS)
Date: 14-06-2011
DOI: 10.1021/LA2006277
Abstract: Adsorption of organic acid at the mineral oxide-electrolyte interface has been explored. The adsorption of 2,4-dihydroxybenzoic acid onto α-alumina illustrates that specific ion effects show up at very low salt concentration (<0.05 mM). These surprising Hofmeister effects occur at salt concentrations an order of magnitude lower than in a previous study ( J. Colloid Interface Sci. 2010, 344, 482 ). Salts enhance adsorption and specifically at ≤0.05 mM. With increasing concentration of ion, the adsorption density decreases. The results are accounted for by incorporating the ion size and dispersion forces in the theoretical modeling based on ab initio calculations of polarizabilities. The order appears to be governed by ion size, determining the maximum concentration that ions can attain near the surface due to close packing.
Publisher: AIP Publishing
Date: 08-07-2019
DOI: 10.1063/1.5096237
Abstract: We resolve a thermodynamic inconsistency in previous theoretical descriptions of the free energy of chemisorption (charge regulation) under conditions where nonelectrostatic physisorption is included, as applied to surface forces and particle-particle interactions. We clarify the role of nonelectrostatic ion physisorption energies and show that a term previously thought to represent physisorbed ion concentrations (activities) should instead be interpreted as a “partial ion activity” based solely on the electrostatic physisorption energy and bulk concentration, or alternatively on the nonelectrostatic physisorption energy and surface concentration. Second, the chemisorption energy must be understood as the change in chemical potential after subtracting the electrostatic energy, not subtracting the physisorption energy. Consequently, a previously reported specific ion nonelectrostatic physisorption contribution to the chemisorption free energy is annulled. We also report a correction to the calculation of surface charge. The distinction in “partial ion activity” evaluated from bulk concentration or from surface concentration opens a way to study nonequilibrium forces where chemisorption is in equilibrium with physisorbed ions but not in equilibrium with bulk ions, e.g., by a jump in ion concentrations.
Publisher: AIP Publishing
Date: 11-1993
DOI: 10.1063/1.465819
Abstract: A molecular potential energy surface has the symmetry properties of invariance to rotation of the whole molecule, inversion of all atomic coordinates, and permutation of indistinguishable nuclei. While some of this invariance character can be easily incorporated in a local description of the surface, a formal application of these symmetry restrictions is useful in considering the form of the global surface which must account for large litude changes of the atomic coordinates. The form of a global molecular potential energy surface as a properly symmetrized analytic function of Cartesian coordinates is derived by extending Molien’s theorem of invariants for finite groups to cover the continuous rotation–inversion group. O(3), and the product of O(3) with the complete nuclear permutation group. The role of so-called redundant internal coordinates in molecular potential energy surfaces is clarified.
Publisher: American Chemical Society (ACS)
Date: 27-03-2012
DOI: 10.1021/JP300533M
Publisher: Elsevier BV
Date: 07-2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2015
DOI: 10.1109/MS.2014.28
Publisher: Springer Berlin Heidelberg
Date: 2009
Publisher: American Chemical Society (ACS)
Date: 03-2019
DOI: 10.1021/ACS.LANGMUIR.8B04176
Abstract: Gas bubbles in a water-filled cavity move upward because of buoyancy. Near the roof, additional forces come into play, such as Lifshitz, double layer, and hydrodynamic forces. Below uncharged metallic surfaces, repulsive Lifshitz forces combined with buoyancy forces provide a way to trap micrometer-sized bubbles. We demonstrate how bubbles of this size can be stably trapped at experimentally accessible distances, the distances being tunable with the surface material. By contrast, large bubbles (≥100 μm) are usually pushed toward the roof by buoyancy forces and adhere to the surface. Gas bubbles with radii ranging from 1 to 10 μm can be trapped at equilibrium distances from 190 to 35 nm. As a model for rock, sand grains, and biosurfaces, we consider dielectric materials such as silica and polystyrene, whereas aluminium, gold, and silver are the ex les of metal surfaces. Finally, we demonstrate that the presence of surface charges further strengthens the trapping by inducing ion adsorption forces.
Publisher: American Chemical Society (ACS)
Date: 17-02-1999
DOI: 10.1021/JP982859X
Publisher: AIP Publishing
Date: 09-1996
DOI: 10.1063/1.472193
Abstract: The Born–Kirkwood–Onsager (BKO) model of solvation, where a solute molecule is positioned inside a cavity cut into a solvent, which is considered as a dielectric continuum, is studied within the bounds of nonlocal electrostatics. The nonlocal cavity model is explicitly formulated and the corresponding nonlocal Poisson equation is reduced to an integral equation describing the behavior of the charge density induced in the medium. It is found that the presence of a cavity does not create singularities in the total electrostatic potential and its normal derivatives. Such singularities appear only in the local limit and are completely dissipated by nonlocal effects. The Born case of a spherical cavity with a point charge at its centre is investigated in detail. The corresponding one-dimensional integral Poisson equation is solved numerically and values for the solvation energy are determined. Several tests of this approach are presented: (a) We show that our integral equation reduces in the local limit to the chief equation of the local BKO theory. (b) We provide certain approximations which enable us to obtain the solution corresponding to the preceding nonlocal treatment of Dogonadze and Kornyshev (DK). (c) We make a comparison with the results of molecular solvation theory (mean spherical approximation), as applied to the calculation of solvation energies of spherical ions.
Publisher: Elsevier BV
Date: 2023
DOI: 10.1016/J.JCIS.2022.10.018
Abstract: The specific effects of salts (strong electrolytes) on biomolecular properties have been investigated for more than a century. By contrast, the specific role of pH buffers (weak electrolytes and their salts) has usually been ignored. Here, specific buffer effects on DNA thermal stability were evaluated by measuring the melting curve of calf thymus DNA through UV-vis spectroscopy. The study was carried out using phosphate, Tris, citrate and cacodylate buffers at fixed pH 7.4 at concentrations varying systematically in the range 1-600 mM. DNA stability increases with buffer concentration and is influenced specifically by buffer type. To interpret empirical data, a theoretical model was applied with parameters quantifying the impact of buffer on the DNA backbone charge. Comparing the buffer effects via buffer ionic strength rather than buffer concentration, we find that the buffers stabilize DNA in the order Tris > cacodylate > phosphate > citrate.
Publisher: American Chemical Society (ACS)
Date: 04-11-2009
DOI: 10.1021/LA903061H
Abstract: A modified Poisson-Boltzmann analysis is made of the double layer interaction between two silica surfaces and two alumina surfaces in chloride electrolyte. The analysis incorporates nonelectrostatic ion-surface dispersion interactions based on ab initio ionic excess polarizabilities with finite ion sizes. A hydration model for the tightly held hydration shell of kosmotropic ions is introduced. A direct Hofmeister series (K > Na > Li) is found at the silica surface while the reversed series (Li > Na > K) is found at alumina, bringing theory in line with experiment for the first time. Calculations with unhydrated ions also suggest that surface-induced dehydration may be occurring at the alumina surface.
Publisher: IEEE
Date: 04-2017
Publisher: American Chemical Society (ACS)
Date: 14-06-2018
Publisher: Frontiers Media SA
Date: 31-10-2014
Publisher: American Chemical Society (ACS)
Date: 13-10-2006
DOI: 10.1021/LA062097U
Abstract: Phase-change emulsions (PCE) are important in a variety of applications, from ultrasound imaging to the explosive material used in the mining industry, but until now there has been no adequate theory to describe their activation properties. The PCE consists of a low-boiling-point liquid, known as the volatile phase, dispersed in an aqueous phase. The volatile phase boils as a result of an increase in the temperature of the emulsion. The volume of the emulsion will increase during this phase transition, with the transition temperature and final volume of the emulsion highly dependent on the initial radius of the liquid droplets. Here a description of the change in boiling point and freezing point of the volatile phase, as well as the volume change of a droplet in the emulsion as a function of the initial droplet radius, is presented. The influence of volatile phase solubility, liquid-liquid interfacial tension, and final temperature are explored, accounting for the influence of confinement on the properties of the volatile phase. Beyond this, a means by which the diffusivity of the gas in the continuous liquid phase can be measured is derived.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA17356J
Abstract: Different 10 mM buffers at the same nominal pH affect specifically the adsorption of lysozyme on ordered mesoporous silica. It emerges that specific buffer effects should be considered within ‘Hofmeister phenomena’.
Publisher: Informa UK Limited
Date: 05-09-2014
DOI: 10.1080/08927014.2014.951341
Abstract: The polychaete, Hydroides elegans, is a tube-building worm that is widely distributed in tropical and subtropical seas. It is a dominant fouling species and thus a major target organism in antifouling research. Here, the first high-throughput proteomic profiling of pre-competent and competent larvae of H. elegans is reported with the identification of 1,519 and 1,322 proteins, respectively. These proteins were associated with a variety of biological processes. However, a large proportion was involved in energy metabolism, redox homeostasis, and microtubule-based processes. A comparative analysis revealed 21 proteins that were differentially regulated in larvae approaching competency.
Publisher: American Physical Society (APS)
Date: 06-10-2006
Publisher: IOP Publishing
Date: 07-2016
Publisher: Informa UK Limited
Date: 10-2016
Start Date: 2020
End Date: 12-2020
Amount: $444,000.00
Funder: Australian Research Council
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