Specific Ion Effects of Salt Solutions at the CaF<sub>2</sub>/Water Interface

Hopkins, Adam J.; Schrödle, Simon; Richmond, Geraldine L.

doi:10.1021/la100607b

Cited by 44 publications

(69 citation statements)

References 41 publications

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“…This is further evidence of the ion complexation that occurs between the COO − head group and Ca 2+ ion in solution. Ion complexation effectively screens the surface charge induced by the deprotonated PA head group, as predicted by Gouy-Chapman theory (114,(130)(131)(132)(133). The screening effect is seen to increase with Ca 2+ concentration, as expected, until the water spectrum for a PA monolayer spread on a 1.8-M CaCl 2 subphase (Figure 6c) resembles the water spectrum for a 1.8-M CaCl 2 solution without a PA monolayer at the vapor/solution interface (Figure 6d), except for the disappearance of the peak at ∼3,700 cm −1 (86).…”

Section: Palmitic Acid Organization and Ion Complexationmentioning

confidence: 88%

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Jubb

Wei

Allen

2012

Annu. Rev. Phys. Chem.

149

263

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The chemistry that occurs at surfaces has been an intense area of study for many years owing to its complexity and importance in describing a wide range of physical phenomena. The vapor/water interface is particularly interesting from an environmental chemistry perspective as this surface plays host to a wide range of chemistries that influence atmospheric and geochemical interactions. The application of vibrational sum frequency generation (VSFG), an inherently surface-specific, even-order nonlinear optical spectroscopy, enables the direct interrogation of various vapor/aqueous interfaces to elucidate the behavior and reaction of chemical species within the surface regime. In this review we discuss the application of VSFG to the study of a variety of atmospherically important systems at the vapor/aqueous interface. Chemical systems presented include inorganic ionic solutions prevalent in aqueous marine aerosols, small molecular solutes, and long-chain fatty acids relevant to fat-coated aerosols. The ability of VSFG to probe both the organization and reactions that may occur for these systems is highlighted. A future perspective toward the application of VSFG to the study of environmental interfaces is also provided.

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Section: Palmitic Acid Organization and Ion Complexationmentioning

confidence: 88%

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Jubb

Wei

Allen

2012

Annu. Rev. Phys. Chem.

149

263

View full text Add to dashboard Cite

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“…The ability to focus on asymmetric environments, together with the fact that symmetry appears to be broken only within a few angstroms of the air-water interface, makes SFG a promising tool to examine the surprising adsorption behavior of small anions (110)(111)(112)(113). Calculations of u z E from simulations with dissolved ions give a sense for how solute-induced spectral changes should be interpreted (101).…”

Section: Surface-sensitive Vibrational Spectroscopymentioning

confidence: 99%

Water Interfaces, Solvation, and Spectroscopy

Geissler

2013

Annu. Rev. Phys. Chem.

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Liquid water consistently expands our appreciation of the rich statistical mechanics that can emerge from simple molecular constituents. Here I review several interrelated areas of recent work on aqueous systems that aim to explore and explain this richness by revealing molecular arrangements, their thermodynamic origins, and the timescales on which they change. Vibrational spectroscopy of OH stretching features prominently in these discussions, with an emphasis on efforts to establish connections between spectroscopic signals and statistics of intermolecular structure. For bulk solutions, the results of these efforts largely verify and enrich existing physical pictures of hydrogen-bond network connectivity, dynamics, and response. For water at interfaces, such pictures are still emerging. As an important example I discuss the solvation of small ions at the air-water interface, whose surface propensities challenge a basic understanding of how aqueous fluctuations accommodate solutes in heterogeneous environments.

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“…For instance, Cl − and Br − disrupt H-bonds at the positively charged TiO 2 /water interface, 14 but they mostly act as simple charge screeners at the positively charged CaF 2 /water interface. 15 EDLs have large impacts on suspension stability, with strong ion dependence. Zeta potential and shear yield stress measurements on amorphous silica suspensions 16 showed substantial shifts of the isoelectric point (pH for which the zeta-potential is zero) depending on alkali chloride concentration and cation identity.…”

Section: ■ Introductionmentioning

confidence: 99%

Electrolytes at the Hydroxylated (0001) α-Quartz/Water Interface: Location and Structural Effects on Interfacial Silanols by DFT-Based MD

Pfeiffer-Laplaud

Gaigeot

2016

J. Phys. Chem. C

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Structural properties of NaCl, KCl, and NaI electrolytes forming an electrical double layer (EDL) at the fully hydroxylated (0001) α-quartz/liquid water interface have been investigated by means of first-principles molecular dynamics simulations (FPMD). Cations are found in inner-sphere conformations, directly bonded on two in-plane silanol groups that replace water molecules that would be present in the first solvation shell of the aqueous cations. Anions are located within the second/third water layer above the surface, fully solvated as in pure liquid water, and cation−anion adopt rather flexible solvent separated ion-pair (SSIP) geometries in the EDL. While the individual solvation shells of the aqua-ions are only slightly affected by ion-pairing at the interface, the silanols at the quartz surface are strongly perturbed. The presence of the electrolytes in the EDL affects more deeply the silanols' geometrical properties than single ions do (J. Phys. Chem. C 2016, 120, 4866−4880): the silanol−silanol intrasurface H-bonding that was observed at the neat interface is extremely weakened by the presence of the electrolytes. Further disordering of the surface silanols is characterized by large changes in their orientation and covalent bond-lengths, regardless of their in-plane (IP) or out-of-plane (OP) orientations. Such structural changes of the surface silanols are tentatively correlated here with an increase in the basicity of all surface sites. ■ INTRODUCTIONIons from electrolytic solutions play key roles in interfacial water/mineral properties. Their adsorption behaviors typically drive pollutant transport in groundwater, 1,2 mineral dissolution, 3 or clay swelling, 4 to name a few. Electrolytes can strongly affect the binding of organic molecules because of competitive adsorption. 5 Even non-adsorbed electrolyte ions can influence adsorption of biomolecules like peptides or DNA 6−9 through conformational changes or ion-pairing.Cations and/or anions from electrolytes get distributed at aqueous solid interfaces so as to form an electrical double layer (EDL). EDLs are known to control the chemical reactivity of the surface, and varying the ionic strength tunes the EDL depth or Debye length. Ionic strength effects can be probed at water/ mineral interfaces via sum frequency generation (SFG) spectroscopy through the indirect knowledge of the interfacial water structural response to the presence of the ions. 10−12 Of particular interest are the electrolyte-induced perturbations on the "ice-like" and "liquid-like" bands in the O−H stretching region. It is well accepted that electrolytes bring interfacial disorder, as evidenced by the intensity shrink of the ice-like vibrational signatures, which in turn shows the disappearance of the strong H-bonds formed by interfacial water molecules. At the fused quartz/water interface, it has been shown that SFG intensities depend on the nature of both cations 13 and anions. 14 From the spectroscopic results, cations with higher surface charge densities induce the largest SFG i...

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Specific Ion Effects of Salt Solutions at the CaF₂/Water Interface

Cited by 44 publications

References 41 publications

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Water Interfaces, Solvation, and Spectroscopy

Electrolytes at the Hydroxylated (0001) α-Quartz/Water Interface: Location and Structural Effects on Interfacial Silanols by DFT-Based MD

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Specific Ion Effects of Salt Solutions at the CaF2/Water Interface

Cited by 44 publications

References 41 publications

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Water Interfaces, Solvation, and Spectroscopy

Electrolytes at the Hydroxylated (0001) α-Quartz/Water Interface: Location and Structural Effects on Interfacial Silanols by DFT-Based MD

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Specific Ion Effects of Salt Solutions at the CaF₂/Water Interface