Mean field theories of ion distributions, such as the Gouy-Chapman theory that describes distribution near a charged planar surface, ignore molecular-scale structure in liquid solution. The predictions vary substantially from our x-ray reflectivity measurements interface between two electrolyte solutions. Molecular dynamics simulations, which include structure, were used to calculate potential mean force on single ion. We this generalized Poisson-Boltzmann equation predict full...

Synchrotron x-ray reflectivity is used to study the interface between bulk water and n-alkanes with carbon numbers 6 through 10, 12, 16, 22. For all interfaces, except water-hexane interface, interfacial width disagrees prediction from capillary-wave theory. The variation of number can be described by combining for a contribution intrinsic structure. This structure determined gyration radius shorter alkanes correlation length longer alkanes.

Agreement between the theoretical and measured resolution dependence of x-ray specular reflection from ${\mathrm{H}}_{2}$O-vapor interface shows that macroscopic capillary model for surface roughness can be extended to length scales as small 400 \AA{}. thermal diffuse scattering data form, with no significant adjustable parameters, independently leads similar conclusions.

Significance The selective separation of targeted metal ions is utilized for environmental remediation, mining rare earth and base metals, as well the isolation long-lived radionuclides from nuclear waste. During process solvent extraction, organic extractant molecules complex with to assist their transfer an aqueous phase. structure ion–extractant complexes at interface, mechanism ion transport across are generally unknown but relevant improving kinetics efficiency this industrial process....

Ion distributions play a central role in various settings—from biology, where they mediate the electrostatic interactions between charged biomolecules solution, to energy storage devices, influence charging properties of supercapacitors. These are determined by dictated chemical ions and their environment as well long-range nature force. Recent theoretical computational studies have explored correlations ions, which been suggested underlie number counterintuitive results, such like-charge...

Selective extraction of metal ions from a complex aqueous mixture into an organic phase is used to separate toxic or radioactive metals polluted environments and nuclear waste, as well produce industrially relevant metals, such rare earth ions. Selectivity arises the choice extractant amphiphile, dissolved in phase, which interacts preferentially with target ion. The extractant-mediated process ion transport takes place at aqueous–organic interface; nevertheless, little known about molecular...

Significance Structural immunology employs static, atomic-level representations to uncover the molecular mechanisms by which immune receptors sensitively discern infection and disease. Lipid membranes, particularly those exposing phosphatidylserine lipids, are now understood be important signals in various aspects of regulation. However, dynamic nature lipid membranes makes standard tools structural poorly suited these systems, leaving a large gap our understanding. Here we implement suite...

Synchrotron X-ray reflectivity is used to study the electron density profile normal bulk water−hexane interface. This first measurement of microscopic interfacial width a neat water−oil interface relied upon development novel technique flatten liquid−liquid The interpreted in terms an error function yield 0.33 ± 0.025 nm. Within context capillary wave theory, it shown that this parameter agreement with macroscopic measurements tension. These are compared computer simulations water−alkane interfaces.

The design of a synchrotron x-ray liquid surface spectrometer at beamline X19C the National Synchrotron Light Source is described. This capable performing full range scattering techniques. A few examples measurements made using this are presented, including studies organic monolayers on water and structure strongly fluctuating oil–microemulsion interfaces. discussed illustrate accuracy, resolution, capabilities spectrometer.

The structure of monolayers ${\mathrm{CH}}_{3}$(${\mathrm{CH}}_{2}$${)}_{22}$COOH on water, along \ensuremath{\sim}21 \ifmmode^\circ\else\textdegree\fi{}C isotherms between 18 and 35 \AA{} $^{2}$/molecule, has been studied with glancing-angle x-ray diffraction specular reflection. Following an incremental area change, in some regions the isotherm, pattern evolves until surface pressure \ensuremath{\pi} is relaxing \ensuremath{\lesssim}0.01 dyn/cm h. Reentrant behavior tilted nontilted phases...

The interfacial behavior of a model solvent extraction liquid-liquid system, consisting solutions dihexadecyl phosphate (DHDP) in dodecane and SrCl2 water, was studied to determine the structure ion-extractant complex its variation with pH. Previous experiments on similar system ErCl3 demonstrated that kinetics process could be greatly retarded by cooling through an adsorption transition, thus providing method immobilize complexes at interface further characterize them X-ray...

Experiments and computer simulations provide a new perspective that strong correlations of counterions with charged nanoparticles can influence the localization at liquid-liquid interfaces support formation voltage-tunable nanoparticle arrays. We show ion condensation onto facilitates their transport from aqueous-side an interface between two immiscible electrolyte solutions to organic-side, but contiguous interface. Counterion highly overcomes electrostatic barrier presented by low...

Numerous applications of liquid crystals rely on control molecular orientation at an interface. However, little is known about the precise structure such interfaces. In this work, synchrotron X-ray reflectivity measurements, accompanied by large-scale atomistic dynamics simulations, are used for first time to reconstruct air-liquid crystal interface a nematic material, namely, 4-pentyl-4'-cyanobiphenyl (5CB). The results compared those 4-octyl-4'-cyanobiphenyl (8CB) which, in addition...

The structure of the fully relaxed phases a Langmuir monolayer tetracosanoic acid is determined by x-ray diffraction and reflection along an isotherm at ∼20.5 °C. Isotherms taken allowing surface pressure to stabilize between incremental compressions are seen be qualitatively different from constant-rate nonrelaxed isotherms typically in literature. At low densities consists inhomogeneous film islands crystalline (or hexatic) phase with molecular tilt ordering that analogous smectic I liquid...

Surfactants have their primary utility, both scientific and industrial, at the liquid-liquid interface. We review recent X-ray surface scattering experiments that probe molecular ordering phase behavior of surfactants water-oil The presence oil modifies interfacial in a manner cannot be understood simply from analogies with studies Langmuir monolayers water-vapor interface or traditional view solvent is fully mixed surfactants. These explored role chain flexibility head group interactions on...

Solvent extraction is used widely for chemical separations and environmental remediation. Although the kinetics efficiency of this process rely upon formation ion-extractant complexes, it has proven challenging to identify location complexation within solution its impact on separation. Here, we use tensiometry X-ray scattering characterize surface aqueous solutions lanthanide chlorides water-soluble extractant bis(2-ethylhexyl) phosphoric acid (HDEHP), in absence a coexisting organic...

Synchrotron x-ray reflectivity is used to study the structure of a monolayer F(CF2)10(CH2)2OH self-assembled at liquid–liquid interface from solution in hexane placed contact with water. It demonstrated that this high density (solid) phase below transition temperature. This contrast conventional expectation soluble surfactants form disordered monolayers interface. Above temperature desorbs into solution, leaving behind an very low surfactants. Hysteresis formation occurs when scanned through...

Adsorption of a binary liquid mixture near criticality onto solid glass substrate can be studied using light reflected off the glass/liquid boundary. Reflectivity data analyzed with modified Landau-Ginzburg theory contact wall interaction are consistent an exponential decay order parameter into bulk. This analysis provides measure ${h}_{1}$, effective strength. The reflectivity also expressed as expansion in moments order-parameter profile. For presented and profile truncated at first-order...

We present X-ray reflectivity and interfacial tension measurements of the electrified liquid/liquid interface between two immiscible electrolyte solutions for purpose understanding dependence ion distributions on applied electric potential difference across interface. The aqueous phase contains alkali-metal chlorides, including LiCl, NaCl, RbCl, or CsCl, organic is a 1,2-dichloroethane solution bis(triphenylphosphor anylidene) ammonium tetrakis(pentafluorophenyl)borate (BTPPATPFB). Selected...

During the solvent extraction of metal ions from an aqueous to organic phase, organic-soluble extractants selectively target aqueous-soluble for transport into phase. In case that are also soluble in our recent studies lanthanide ion-extractant complexes at surface solutions suggested complexation phase can hinder process. Here, we investigate a similar phenomenon relevant separation Co(II), Ni(II), and Fe(III). X-ray fluorescence near total reflection tensiometry used characterize ion...

Synchrotron X-ray reflectivity is used to study the electron density profile normal interface between bulk water and n-docosane (C22H46). These measurements are interpreted in terms of an error function yield interfacial width 5.7 ± 0.2 Å. In contrast with earlier measurement on water−hexane interface, this disagrees sharply prediction from capillary wave theory, σcap = 3.5 This can be accounted for by combining a contribution intrinsic structure due correlation length docosane. We also...

We report the results of experimental studies equation state and structure water-supported monolayers semifluorinated hydrocarbons F(CF2)8(CH2)12H, F(CF2)10(CH2)11H F(CF2)12(CH2)18H at temperatures from 4 to 30 °C. find that these molecules are metastable stable, stability improves as length fluorinated block increases. Grazing-incidence X-ray diffraction measurements monolayer show it is capable forming ordered structures defined by hexagonal close packing blocks adsorbed molecules. This...