The liquid surface/interface spectrometer at ChemMatCARS synchrotron facility at the Advanced Photon Source

Lin, Binhua; Meron, Mati; Gebhardt, Jeff; Graber, Tim; Schlossman, Mark L.; Viccaro, P.J.

doi:10.1016/s0921-4526(03)00272-2

Cited by 52 publications

(51 citation statements)

References 9 publications

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“…X-ray reflectivity, RðQ z Þ, is measured as a function of wave vector transfer normal to the interface, Q z = ð4π=λÞsinðαÞ, where λ is the X-ray wavelength and α is the angle of incidence. X-ray reflectivity measurements were carried out at the ChemMatCARS Sector 15 of the Advanced Photon Source on a liquid surface reflectometer at an X-ray energy of 30 keV (11,39). Reflectivity is defined as the reflected intensity normalized to the incident intensity (after subtraction of background scattering) (40).…”

Section: Methodsmentioning

confidence: 99%

Tuning ion correlations at an electrified soft interface

Laanait

Mihaylov

Hou

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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101

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Ion distributions play a central role in various settings-from biology, where they mediate the electrostatic interactions between charged biomolecules in solution, to energy storage devices, where they influence the charging properties of supercapacitors. These distributions are determined by interactions dictated by the chemical properties of the ions and their environment as well as the long-range nature of the electrostatic force. Recent theoretical and computational studies have explored the role of correlations between ions, which have been suggested to underlie a number of counterintuitive results, such as like-charge attraction. However, the interdependency between ion correlations and other interactions that ions experience in solution complicates the connection between physical models of ion correlations and the experimental investigation of ion distributions. We exploit the properties of the liquid/liquid interface to vary the coupling strength Γ of ion-ion correlations from weak to strong while monitoring their influence on ion distributions at the nanometer scale with X-ray reflectivity and the macroscopic scale with interfacial tension measurements. These data are in agreement with the predictions of a parameterfree density functional theory that includes ion-ion correlations and ion-solvent interactions over the entire range of experimentally tunable correlation coupling strengths (from 0.8 to 3.7). This study provides evidence for a sharply defined electrical double layer for large coupling strengths in contrast to the diffuse distributions predicted by mean field theory, thereby confirming a common prediction of many ion correlation models. The reported findings represent a significant advance in elucidating the nature and role of ion correlations in charged soft matter.liquid surface scattering | ion density profile | surface excess charge | Poisson-Boltzmann | Debye-Hückel hole T he works by Gouy (1) and Chapman (2) introduced the Poisson-Boltzmann (PB) equation to describe the distribution of ions and the accompanying variation of electric potential at the interface between a charged planar electrode and an electrolyte solution (1, 2). This seminal theory considered point-like ions interacting through their mean electric field in a continuum solvent but neglected both chemically specific ion-solvent interactions and correlations between ions. Specific ion interactions are exemplified by the well-known Hofmeister series (3). The study of ion correlations has been motivated by observations of the reentrant condensation of DNA (4) and proteins (5) in solution, in which like-charged biomolecules aggregate in the presence of multivalent ions, and reports of charge reversal in colloidal suspensions, in which the sign of the screened charge on a colloid can be changed by varying the surrounding electrolyte solution (6, 7).Correlations between ions that are caused by their electrostatic interactions are expected to be important when the average electrostatic interaction energy between neighboring ions...

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Section: Methodsmentioning

confidence: 99%

Tuning ion correlations at an electrified soft interface

Laanait

Mihaylov

Hou

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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101

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“…X-ray reflectivity was measured at the ChemMatCARS beamline 15-ID at the Advanced Photon Source (Argonne National Laboratory, USA) with a liquid surface instrument and measurement techniques described in detail elsewhere [55,[64][65][66]. The reflectivity data were measured as a function of the wave vector transfer normal to the interface, Q z = k scat À k in = (4p/k)sin a (the in-plane wave vector components Q x = Q y = 0 where k = 0.41360 ± 0.00005 Å is the X-ray wavelength and a is the angle of reflection) (Fig.…”

Section: X-ray Methodsmentioning

confidence: 99%

Ion distributions at the nitrobenzene–water interface electrified by a common ion

Luo

Málková

Yoon

et al. 2006

Journal of Electroanalytical Chemistry

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Synchrotron X-ray reflectivity is used to study ion distributions at the liquid-liquid interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate (TBATPB) and a water solution of tetrabutylammonium bromide (TBABr). The concentration of TBABr is varied to alter the ion distribution. Our X-ray measurements are inconsistent with several commonly used theories of ion distributions, including Gouy-Chapman, modified Verwey-Niessen, and the MPB5 version of the Poisson-Boltzmann equation. These structural measurements are described well by ion distributions predicted by a version of the Poisson-Boltzmann equation that explicitly includes a free energy profile for ion transfer across the interface when this profile is described by a simple analytic form or by a potential of mean force from molecular dynamics simulations. These X-ray measurements from the liquid-liquid interface provide evidence for the importance of interfacial liquid structure in determining interfacial ion distributions.

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“…Details of the experimental setup and utilization of Pilatus detector at pinhole mode have been reported previously [20][21][22]. We also repeated the experiments at sector X14A of National Synchrotron Light Source (NSLS) to confirm that the results were not artifacts of the setup or the beam.…”

mentioning

confidence: 88%