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Devlin SW, Bernal F, Riffe EJ, Wilson KR, Saykally RJ. Spiers Memorial Lecture: Water at interfaces. Faraday Discuss 2024; 249:9-37. [PMID: 37795954 DOI: 10.1039/d3fd00147d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
In this article we discuss current issues in the context of the four chosen subtopics for the meeting: dynamics and nano-rheology of interfacial water, electrified/charged aqueous interfaces, ice interfaces, and soft matter/water interfaces. We emphasize current advances in both theory and experiment, as well as important practical manifestations and areas of unresolved controversy.
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Affiliation(s)
- Shane W Devlin
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Franky Bernal
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Erika J Riffe
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Richard J Saykally
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
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Devlin SW, Jamnuch S, Xu Q, Chen AA, Qian J, Pascal TA, Saykally RJ. Agglomeration Drives the Reversed Fractionation of Aqueous Carbonate and Bicarbonate at the Air-Water Interface. J Am Chem Soc 2023; 145:22384-22393. [PMID: 37774115 DOI: 10.1021/jacs.3c05093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023]
Abstract
In the course of our investigations of the adsorption of ions to the air-water interface, we previously reported the surprising result that doubly charged carbonate anions exhibit a stronger surface affinity than singly charged bicarbonate anions. In contrast to monovalent, weakly hydrated anions, which generally show enhanced concentrations in the interfacial region, multivalent (and strongly hydrated) anions are expected to show a much weaker surface propensity. In the present work, we use resonantly enhanced deep-UV second-harmonic generation spectroscopy to measure the Gibbs free energy of adsorption of both carbonate (CO32-) and bicarbonate (HCO3-) anions to the air-water interface. Contrasting the predictions of classical electrostatic theory and in support of our previous findings from X-ray photoelectron spectroscopy, we find that carbonate anions do indeed exhibit much stronger surface affinity than do the bicarbonate anions. Extensive computer simulations reveal that strong ion pairing of CO32- with the Na+ countercation in the interfacial region results in the formation of near-neutral agglomerate clusters, consistent with a theory of interfacial ion adsorption based on hydration free energy and capillary waves. Simulated X-ray photoelectron spectra predict a 1 eV shift in the carbonate spectra compared to that of bicarbonate, further confirming our experiments. These findings not only advance our fundamental understanding of ion adsorption chemistry but also impact important practical processes such as ocean acidification, sea-spray aerosol chemistry, and mammalian respiration physiology.
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Affiliation(s)
- Shane W Devlin
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
| | - Sasawat Jamnuch
- ATLAS Materials Science Laboratory, Department of Nano Engineering and Chemical Engineering, University of California, San Diego, La Jolla, California 92023, United States
| | - Qiang Xu
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
| | - Amanda A Chen
- ATLAS Materials Science Laboratory, Department of Nano Engineering and Chemical Engineering, University of California, San Diego, La Jolla, California 92023, United States
| | - Jin Qian
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
| | - Tod A Pascal
- ATLAS Materials Science Laboratory, Department of Nano Engineering and Chemical Engineering, University of California, San Diego, La Jolla, California 92023, United States
- Materials Science and Engineering, University of California San Diego, La Jolla, California 92023, United States
- Sustainable Power and Energy Center, University of California San Diego, La Jolla, California 92023, United States
| | - Richard J Saykally
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
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Premadasa UI, Bocharova V, Lin L, Genix AC, Heller WT, Sacci RL, Ma YZ, Thiele NA, Doughty B. Tracking Molecular Transport Across Oil/Aqueous Interfaces: Insight into "Antagonistic" Binding in Solvent Extraction. J Phys Chem B 2023. [PMID: 37216432 DOI: 10.1021/acs.jpcb.3c00386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Liquid/liquid (L/L) interfaces play a key, yet poorly understood, role in a range of complex chemical phenomena where time-evolving interfacial structures and transient supramolecular assemblies act as gatekeepers to function. Here, we employ surface-specific vibrational sum frequency generation combined with neutron and X-ray scattering methods to track the transport of dioctyl phosphoric acid (DOP) and di-(2-ethylhexyl) phosphoric acid (DEHPA) ligands used in solvent extraction at buried oil/aqueous interfaces away from equilibrium. Our results show evidence for a dynamic interfacial restructuring at low ligand concentrations in contrast to expectation. These time-varying interfaces arise from the transport of sparingly soluble interfacial ligands into the neighboring aqueous phase. These results support a proposed "antagonistic" role of ligand complexation in the aqueous phase that could serve as a holdback mechanism in kinetic liquid extractions. These findings provide new insights into interfacially controlled chemical transport at L/L interfaces and how these interfaces vary chemically, structurally, and temporally in a concentration-dependent manner and present potential avenues to design selective kinetic separations.
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Affiliation(s)
- Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Vera Bocharova
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Lu Lin
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Anne-Caroline Genix
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, F-34095 Montpellier, France
| | - William T Heller
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Nikki A Thiele
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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On the mechanisms of ion adsorption to aqueous interfaces: air-water vs. oil-water. Proc Natl Acad Sci U S A 2022; 119:e2210857119. [PMID: 36215494 PMCID: PMC9586313 DOI: 10.1073/pnas.2210857119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The adsorption of ions to water-hydrophobe interfaces influences a wide range of phenomena, including chemical reaction rates, ion transport across biological membranes, and electrochemical and many catalytic processes; hence, developing a detailed understanding of the behavior of ions at water-hydrophobe interfaces is of central interest. Here, we characterize the adsorption of the chaotropic thiocyanate anion (SCN-) to two prototypical liquid hydrophobic surfaces, water-toluene and water-decane, by surface-sensitive nonlinear spectroscopy and compare the results against our previous studies of SCN- adsorption to the air-water interface. For these systems, we observe no spectral shift in the charge transfer to solvent spectrum of SCN-, and the Gibb's free energies of adsorption for these three different interfaces all agree within error. We employed molecular dynamics simulations to develop a molecular-level understanding of the adsorption mechanism and found that the adsorption for SCN- to both water-toluene and water-decane interfaces is driven by an increase in entropy, with very little enthalpic contribution. This is a qualitatively different mechanism than reported for SCN- adsorption to the air-water and graphene-water interfaces, wherein a favorable enthalpy change was the main driving force, against an unfavorable entropy change.
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Benjamin I. Structure, Thermodynamics, and Dynamics of Thiocyanate Ion Adsorption and Transfer across the Water/Toluene Interface. J Phys Chem B 2022; 126:5706-5714. [PMID: 35861680 DOI: 10.1021/acs.jpcb.2c03956] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations are used to examine in detail the structure, thermodynamics, and dynamics involve in the adsorption and transfer of the thiocyanate ion (SCN-) across the water/toluene interface. Free energy, hydration structure, and several dynamical properties as a function of the ion location along the interface normal are calculated and contrasted with recent experiments. The free energy profile exhibits a local minimum near the interface corresponding to adsorption free energy relative to bulk water of -6 kJ/mol, in reasonable agreement with experiments. The simulations provide insight into the water surface fluctuations that are coupled to the ion transfer, demonstrating formation of water finger-like structures assisting the transfer process.
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Affiliation(s)
- Ilan Benjamin
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
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