1
|
Hunger J, Schaefer J, Ober P, Seki T, Wang Y, Prädel L, Nagata Y, Bonn M, Bonthuis DJ, Backus EHG. Nature of Cations Critically Affects Water at the Negatively Charged Silica Interface. J Am Chem Soc 2022; 144:19726-19738. [PMID: 36273333 PMCID: PMC9634801 DOI: 10.1021/jacs.2c02777] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Understanding the collective behavior of ions at charged
surfaces
is of paramount importance for geological and electrochemical processes.
Ions screen the surface charge, and interfacial fields break the centro-symmetry
near the surface, which can be probed using second-order nonlinear
spectroscopies. The effect of electrolyte concentration on the nonlinear
optical response has been semi-quantitatively explained by mean-field
models based on the Poisson–Boltzmann equation. Yet, to explain
previously reported ion-specific effects on the spectroscopic response,
drastic ion-specific changes in the interfacial properties, including
surface acidities and dielectric permittivities, or strong ion adsorption/desorption
had to be invoked. Here, we use sum-frequency generation (SFG) spectroscopy
to probe the symmetry-breaking of water molecules at a charged silica
surface in contact with alkaline metal chloride solutions (LiCl, NaCl,
KCl, and CsCl) at various concentrations. We find that the water response
varies with the cation: the SFG response is markedly enhanced for
LiCl compared to CsCl. We show that within mean-field models, neither
specific ion–surface interactions nor a reduced dielectric
constant of water near the interface can account for the variation
of spectral intensities with cation nature. Molecular dynamics simulations
confirm that the decay of the electrochemical potential only weakly
depends on the salt type. Instead, the effect of different salts on
the optical response is indirect, through the reorganization of the
interfacial water: the salt-type-dependent alignment of water directly
at the interface can explain the observations.
Collapse
Affiliation(s)
- Johannes Hunger
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Jan Schaefer
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Patrick Ober
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Takakazu Seki
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Yongkang Wang
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Leon Prädel
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Yuki Nagata
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Mischa Bonn
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Douwe Jan Bonthuis
- Institute of Theoretical and Computational Physics, Graz University of Technology, Petersgasse16/II, 8010Graz, Austria
| | - Ellen H. G. Backus
- Department for Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
- Faculty of Chemistry, Institute of Physical Chemistry, University of Vienna, Währinger Strasse 42, 1090Vienna, Austria
| |
Collapse
|
2
|
Nguyen CV, Peng M, Duignan TT, Nguyen AV. Salting-Up of Surfactants at the Surface of Saline Water as Detected by Tensiometry and SFG and Supported by Molecular Dynamics Simulation. J Phys Chem B 2022; 126:1063-1075. [PMID: 35103476 DOI: 10.1021/acs.jpcb.1c08114] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Surfactant adsorption at the air-water interface is critical to many industrial processes but its dependence on salt ions is still poorly understood. Here, we investigate the adsorption of sodium dodecanoate onto the air-water interface using model saline waters of Li+ or Cs+ at pH values 8 and 11. Both cations enhance the surfactant adsorption, as expected, but their largest effects on the adsorption also depend on pH. Specifically, surface tension measurements, sum-frequency generation spectroscopy, and microelectrophoresis show that small (hard) Li+ enhances the surfactant adsorption more than large (soft) Cs+ at pH 11. This effect is fully reversed at pH 8. We argue that this salting-up (increasing adsorption) reversal is attributable to the conversion of the neutralized carboxylic (-COOH) headgroup at pH 8 into the charged carboxylate (-COO-) headgroup at pH 11, which, respectively, interact with Cs+ and Li+ favorably. Molecular dynamics simulation shows that the affinity of Cs+ to the interface is decreased and eventually overtaken by Li+ as the carboxylic groups are deprotonated. This study highlights the importance of the charge and size of salt ions in selecting surfactants and electrolytes for industrial applications.
Collapse
Affiliation(s)
- Cuong V Nguyen
- School of Chemical Engineering and ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals (UQ Node), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mengsu Peng
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Timothy T Duignan
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Anh V Nguyen
- School of Chemical Engineering and ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals (UQ Node), The University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
3
|
Zhu H, Zhang Y, Pan G, Yang F, Chen J, Min F, Zhu J. Study on bubble penetrating solution/frother interface in the presence of ions. POWDER TECHNOL 2022. [DOI: 10.1016/j.powtec.2022.117139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
4
|
Khan MR, Premadasa UI, Cimatu KLA. Role of the cationic headgroup to conformational changes undergone by shorter alkyl chain surfactant and water molecules at the air-liquid interface. J Colloid Interface Sci 2020; 568:221-233. [DOI: 10.1016/j.jcis.2020.02.056] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/13/2020] [Accepted: 02/14/2020] [Indexed: 01/03/2023]
|
5
|
Wang F, Li X, Zhang F, Liu X, Hu P, Beke-Somfai T, Lu X. Revealing Interfacial Lipid Hydrolysis Catalyzed by Phospholipase A 1 at Molecular Level via Sum Frequency Generation Vibrational Spectroscopy and Fluorescence Microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:12831-12838. [PMID: 31475518 DOI: 10.1021/acs.langmuir.9b02284] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The interfacial hydrolysis of phospholipids catalyzed by phospholipase A1 (PLA1) was studied via sum frequency generation (SFG) vibrational spectroscopy and fluorescence microscopy. Both monolayer and bilayer setups were used to confirm the hydrolysis mechanism. During the hydrolysis, lysophospholipids, one of the hydrolysis products, were desorbed from the interface into the solution, while the other products, fatty acids, self-organized and accumulated with PLA1 at the interface to form the PLA1-induced regions, which can serve as nonspecific binding domains for proteins and thus lead to human vascular diseases. This experimental study provides the essential information on revealing the interfacial biochemical process related to the metabolism of the lipids, which is one of the basic building blocks for cells.
Collapse
Affiliation(s)
- Feng Wang
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| | - Xu Li
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| | - Furong Zhang
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| | - Xiaoyang Liu
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| | - Pengcheng Hu
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| | - Tamás Beke-Somfai
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences , Hungarian Academy of Sciences , H-1117 Budapest , Hungary
| | - Xiaolin Lu
- Department of Biomedical Engineering , Southeast University , Nanjing , Jiangsu 210096 , China
| |
Collapse
|
6
|
García Rey N, Weißenborn E, Schulze-Zachau F, Gochev G, Braunschweig B. Quantifying Double-Layer Potentials at Liquid-Gas Interfaces from Vibrational Sum-Frequency Generation. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:1279-1286. [PMID: 30713590 PMCID: PMC6354727 DOI: 10.1021/acs.jpcc.8b10097] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/13/2018] [Indexed: 05/31/2023]
Abstract
Vibrational sum-frequency generation (SFG) spectroscopy is demonstrated as a fast method to quantify variations of the electric double-layer potential ϕ0 at liquid-gas interfaces. For this, mixed solutions of nonionic tetraethyleneglycol-monodecylether (C10E4) and cationic hexadecyltrimethylammonium bromide (C16TAB) surfactants were investigated using SFG spectroscopy and a thin-film pressure balance (TFPB). Derjaguin-Landau-Verwey-Overbeek analysis of disjoining pressure isotherms obtained with the TFPB technique provides complementary information on ϕ0, which we apply to validate the results from SFG spectroscopy. By using a single ϕ0 value, we can disentangle χ(2) and χ(3) contributions to the O-H stretching modes of interfacial water molecules in the SFG spectra. Having established the latter, we show that unknown double-layer potentials at the liquid-gas interface from solutions with different C16TAB/C10E4 mixing ratios can be obtained from an analysis of SFG spectra and are in excellent agreement with the complementary results from the TFPB technique.
Collapse
|
7
|
Schulze-Zachau F, Bachmann S, Braunschweig B. Effects of Ca 2+ Ion Condensation on the Molecular Structure of Polystyrene Sulfonate at Air-Water Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:11714-11722. [PMID: 30188134 PMCID: PMC6170951 DOI: 10.1021/acs.langmuir.8b02631] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/05/2018] [Indexed: 06/02/2023]
Abstract
The structure of poly(sodium 4-styrenesulfonate) (NaPSS) polyelectrolytes at air-water interfaces was investigated with tensiometry, ellipsometry, and vibrational sum-frequency generation (SFG) in the presence of low and high CaCl2 concentrations. In addition, we have studied the foaming behavior of 20 mM NaPSS solutions to relate the PSS molecular structure at air-water interfaces to foam properties. PSS polyelectrolytes without additional salt exhibited significant surface activity, which can be tuned further by additions of CaCl2. The hydrophobicity of the backbone due to incomplete sulfonation during synthesis is one origin, whereas the effective charge of the polyelectrolyte chain is shown to play another major role. At low salt concentrations, we propose that the polyelectrolyte is forming a layered structure. The hydrophobic parts are likely to be located directly at the interface in loops, whereas the hydrophilic parts are at low concentrations stretched out into near-interface regions in tails. Increasing the Ca2+ concentration leads to ion condensation, a collapse of the tails, and likely to Ca2+ intra- and intermolecular bridges between polyelectrolytes at the interface. The increase in both surface excess and foam stability originates from changes in the polyelectrolyte's hydrophobicity due to Ca2+ condensation onto the PSS polyanions. Consequently, charge screening at the interface is enhanced and repulsive electrostatic interactions are reduced. Furthermore, SFG spectra of O-H stretching bands reveal a decrease in intensity of the low-frequency branch when c(Ca2+) is increased whereas the high-frequency branch of O-H stretching modes persists even for 1 M CaCl2. This originates from the remaining net charge of the PSS polyanions at the air-water interface that is not fully compensated by condensation of Ca2+ ions and leads to electric-field-induced contributions to the SFG spectra of interfacial H2O. A charge reversal of the PSS net charge at the air-water interface is not observed and is consistent with bulk electrophoretic mobility measurements.
Collapse
Affiliation(s)
- Felix Schulze-Zachau
- Institute
of Physical Chemistry and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany
| | - Silvia Bachmann
- Institute
of Particle Technology (LFG), Friedrich-Alexander-Universität
Erlangen-Nürnberg (FAU), Cauerstraße 4, 91058 Erlangen, Germany
| | - Björn Braunschweig
- Institute
of Physical Chemistry and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany
| |
Collapse
|