Reaction Dynamics at Liquid Interfaces

Benjamin, Ilan

doi:10.1146/annurev-physchem-040214-121428

Cited by 60 publications

(52 citation statements)

References 135 publications

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“…In recent years, MD simulations have clarified the role of interfacial fluctuations in the case of ion transport across bare electrochemically controlled interfaces, although the mechanism of transport under these conditions remains under investigation (23). The degree to which interfacial fluctuations play an important role in the extractant-assisted ion transport processes discussed here is also an open issue.…”

Section: Significancementioning

confidence: 98%

Nanoscale view of assisted ion transport across the liquid–liquid interface

Liang

Schweighofer

et al. 2018

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

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116

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During solvent extraction, amphiphilic extractants assist the transport of metal ions across the liquid-liquid interface between an aqueous ionic solution and an organic solvent. Investigations of the role of the interface in ion transport challenge our ability to probe fast molecular processes at liquid-liquid interfaces on nanometer-length scales. Recent development of a thermal switch for solvent extraction has addressed this challenge, which has led to the characterization by X-ray surface scattering of interfacial intermediate states in the extraction process. Here, we review and extend these earlier results. We find that trivalent rare earth ions, Y(III) and Er(III), combine with bis(hexadecyl) phosphoric acid (DHDP) extractants to form inverted bilayer structures at the interface; these appear to be condensed phases of small ion-extractant complexes. The stability of this unconventional interfacial structure is verified by molecular dynamics simulations. The ion-extractant complexes at the interface are an intermediate state in the extraction process, characterizing the moment at which ions have been transported across the aqueous-organic interface, but have not yet been dispersed in the organic phase. In contrast, divalent Sr(II) forms an ion-extractant complex with DHDP that leaves it exposed to the water phase; this result implies that a second process that transports Sr(II) across the interface has yet to be observed. Calculations demonstrate that the budding of reverse micelles formed from interfacial Sr(II) ion-extractant complexes could transport Sr(II) across the interface. Our results suggest a connection between the observed interfacial structures and the extraction mechanism, which ultimately affects the extraction selectivity and kinetics.

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Section: Significancementioning

confidence: 98%

Nanoscale view of assisted ion transport across the liquid–liquid interface

Liang

Schweighofer

et al. 2018

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

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116

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“…12 It is known that deviations from ideal solvent behavior are related to specific ion effects. [13][14] Although recent experimental, 11,[15][16][17] computational, 18 and theoretical [19][20] advances have improved our understanding considerably, the emerging view is that specific ion effects may not have a single unified explanation, especially when ion-ion interactions and interfacial ion-binding sites are operative. 17 The interfacial interactions of biologically relevant, and usually lighter, ions in aqueous environments have been extensively studied.…”

Section: Introductionmentioning

confidence: 99%

Heavy Anionic Complex Creates a Unique Water Structure at a Soft Charged Interface

et al. 2018

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Ion hydration and interfacial water play crucial roles in numerous phenomena ranging from biological to industrial systems. Although biologically relevant (and mostly smaller) ions have been studied extensively in this context, very little experimental data exist about molecular scale behavior of heavy ions and their complexes at interfaces, especially under technologically significant conditions. It has recently been shown that PtCl6 2complexes adsorb at positively charged interfaces in a two-step process that cannot fit into well-known empirical trends, such as Hofmeister series. Here, a combined vibrational sum frequency generation and molecular dynamics study reveals that a unique interfacial water structure is connected to this peculiar adsorption behavior. A novel sub-ensemble analysis of MD simulation results show that after adsorption, PtCl6 2complexes partially retain their first and second hydration spheres, and it is possible to identify three different types of water molecules around them based on their orientational structures and hydrogen bonding strengths. These results have important implications for relating interfacial water structure and hydration enthalpy to the general understanding of specific ion effects. This in turn influences interpretation of heavy metal ion distribution across and reactivity within, liquid interfaces.

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“…In Section 2, we highlight experiments that demonstrate this utility. Relative to solids, the liquid interface is less defined and more structurally complex (13,14). The existence of surface-specific chemical and physical phenomena (15) suggests that the gas-liquid interface can function as a reaction medium distinct from vacuum and from bulk liquid.…”

Section: Introductionmentioning

confidence: 99%

Atomic and Molecular Collisions at Liquid Surfaces

Tesa-Serrate

Smoll

Minton

et al. 2016

Annu. Rev. Phys. Chem.

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The gas-liquid interface remains one of the least explored, but nevertheless most practically important, environments in which molecular collisions take place. These molecular-level processes underlie many bulk phenomena of fundamental and applied interest, spanning evaporation, respiration, multiphase catalysis, and atmospheric chemistry. We review here the research that has, during the past decade or so, been unraveling the molecular-level mechanisms of inelastic and reactive collisions at the gas-liquid interface. Armed with the knowledge that such collisions with the outer layers of the interfacial region can be unambiguously distinguished, we show that the scattering of gas-phase projectiles is a promising new tool for the interrogation of liquid surfaces with extreme surface sensitivity. Especially for reactive scattering, this method also offers absolute chemical selectivity for the groups that react to produce a specific observed product.

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Reaction Dynamics at Liquid Interfaces

Cited by 60 publications

References 135 publications

Nanoscale view of assisted ion transport across the liquid–liquid interface

Nanoscale view of assisted ion transport across the liquid–liquid interface

Heavy Anionic Complex Creates a Unique Water Structure at a Soft Charged Interface

Atomic and Molecular Collisions at Liquid Surfaces

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