1
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Schneck E, Reed J, Seki T, Nagata Y, Kanduč M. Experimental and simulation-based characterization of surfactant adsorption layers at fluid interfaces. Adv Colloid Interface Sci 2024; 331:103237. [PMID: 38959812 DOI: 10.1016/j.cis.2024.103237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 06/10/2024] [Accepted: 06/13/2024] [Indexed: 07/05/2024]
Abstract
Adsorption of surfactants to fluid interfaces occurs in numerous technological and daily-life contexts. The coverage at the interface and other properties of the formed adsorption layers determine the performance of a surfactant with regard to the desired application. Given the importance of these applications, there is a great demand for the comprehensive characterization and understanding of surfactant adsorption layers. In this review, we provide an overview of suitable experimental and simulation-based techniques and review the literature in which they were used for the investigation of surfactant adsorption layers. We come to the conclusion that, while these techniques have been successfully applied to investigate Langmuir monolayers of water-insoluble surfactants, their application to the study of Gibbs adsorption layers of water-soluble surfactants has not been fully exploited. Finally, we emphasize the great potential of these methods in providing a deeper understanding of the behavior of soluble surfactants at interfaces, which is crucial for optimizing their performance in various applications.
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Affiliation(s)
- Emanuel Schneck
- Department of Physics, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany.
| | - Joshua Reed
- Department of Physics, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany
| | - Takakazu Seki
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, 036-8561 Aomori, Japan
| | - Yuki Nagata
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Matej Kanduč
- Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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2
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Pei R, Tan J, Luo Y, Ye S. Close Packing in Trans Conformers Promotes the Formation of Supramolecular Structures with C 1 Symmetry. J Phys Chem Lett 2024; 15:8797-8803. [PMID: 39166774 DOI: 10.1021/acs.jpclett.4c01857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
Assemblies with C1 symmetry exhibit important applications in many fields such as enantioselective catalysis. However, their formation is challenging due to their large entropic disadvantage, and molecular information on their formation dynamics is limited because of the lack of effective characterization techniques. Here, using achiral amphiphilic molecules such as N-oleoyl ethanolamide (OEA) and its analogues as modeling assembly units, we demonstrated that the sss polarization signals, generated by femtosecond sum frequency generation vibrational spectroscopy (SFG-VS), provide a powerful tool to monitor the formation dynamics of the C1 symmetric supramolecular structures at the interfaces. The trans conformation of the assembly units can provide strong π-π interactions and thus produce enough enthalpy to drive the formation of C1 symmetric supramolecular structures. However, the cis conformation impedes the assembly of C1 symmetric structures and cannot generate sss and chiral polarization SFG signals. These findings may aid in rationally constructing ordered and functional superstructures and understanding the mechanism of chirality formation.
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Affiliation(s)
- Ruoqi Pei
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
| | - Junjun Tan
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
| | - Yi Luo
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
| | - Shuji Ye
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
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3
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Yu CC, Seki T, Chiang KY, Wang Y, Bonn M, Nagata Y. Depth-profiling alkyl chain order in unsaturated lipid monolayers on water. J Chem Phys 2024; 160:114902. [PMID: 38506293 DOI: 10.1063/5.0190519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 02/28/2024] [Indexed: 03/21/2024] Open
Abstract
Unsaturated lipids with C=C groups in their alkyl chains are widely present in the cell membrane and food. The C=C groups alter the lipid packing density, membrane stability, and persistence against lipid oxidation. Yet, molecular-level insights into the structure of the unsaturated lipids remain scarce. Here, we probe the molecular structure and organization of monolayers of unsaturated lipids on the water surface using heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy. We vary the location of the C=C in the alkyl chain and find that at high lipid density, the location of the C=C group affects neither the interfacial water organization nor the tail of the alkyl chain. Based on this observation, we use the C=C stretch HD-SFG response to depth-profile the alkyl chain conformation of the unsaturated lipid. We find that the first 1/3 of carbon atoms from the headgroup are relatively rigid, oriented perpendicular to the surface. In contrast, the remaining carbon atoms can be approximated as free rotators, introducing the disordering of the alkyl chains.
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Affiliation(s)
- Chun-Chieh Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Takakazu Seki
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, 036-8561 Aomori, Japan
| | - Kuo-Yang Chiang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yongkang Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yuki Nagata
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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4
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Seki T, Yu CC, Chiang KY, Yu X, Sun S, Bonn M, Nagata Y. Spontaneous Appearance of Triiodide Covering the Topmost Layer of the Iodide Solution Interface Without Photo-Oxidation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:3830-3837. [PMID: 38353041 PMCID: PMC10902846 DOI: 10.1021/acs.est.3c08243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Ions containing iodine atoms at the vapor-aqueous solution interfaces critically affect aerosol growth and atmospheric chemistry due to their complex chemical nature and multivalency. While the surface propensity of iodide ions has been intensely discussed in the context of the Hofmeister series, the stability of various ions containing iodine atoms at the vapor-water interface has been debated. Here, we combine surface-specific sum-frequency generation (SFG) vibrational spectroscopy with ab initio molecular dynamics simulations to examine the extent to which iodide ions cover the aqueous surface. The SFG probe of the free O-D stretch mode of heavy water indicates that the free O-D group density decreases drastically at the interface when the bulk NaI concentration exceeds ∼2 M. The decrease in the free O-D group density is attributed to the spontaneous appearance of triiodide that covers the topmost interface rather than to the surface adsorption of iodide. This finding demonstrates that iodide is not surface-active, yet the highly surface-active triiodide is generated spontaneously at the water-air interface, even under dark and oxygen-free conditions. Our study provides an important first step toward clarifying iodine chemistry and pathways for aerosol formation.
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Affiliation(s)
- Takakazu Seki
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
| | - Chun-Chieh Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Kuo-Yang Chiang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Xiaoqing Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Shumei Sun
- Department of Physics, Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yuki Nagata
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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5
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Musegades LJ, Curtin OP, Cyran JD. Determining the Surface p Ka of Perfluorooctanoic Acid. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:1946-1951. [PMID: 38352857 PMCID: PMC10860129 DOI: 10.1021/acs.jpcc.3c07235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 02/16/2024]
Abstract
Perfluorooctanoic acid (PFOA) is an environmentally prevalent and persistent organic pollutant with toxic and bioaccumulative properties. Despite the known importance of perfluorinated pollutants in the global environment, molecular-level details of the physicochemical behavior of PFOA on aqueous interfaces remain poorly understood. Here, we utilized two surface-specific techniques, vibrational sum frequency generation spectroscopy (SFG) and surface tensiometry, to investigate the pH-induced structural changes of PFOA and octanoic acid (OA) and determined the apparent pKa at the air-water surface. The SFG spectra and surface activity model were investigated over a wide range of pHs. With the surface tension measurements, the surface pKa values for OA and PFOA are determined to be 3.8 ± 0.1 and 2.2 ± 0.2, respectively. These results could provide insights into improved remediation of PFOAs and may impact climate modeling of perfluorinated alkyl chain molecules.
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Affiliation(s)
| | - Owen P. Curtin
- Boise
State University, Boise, Idaho 83725, United States of America
| | - Jenée D. Cyran
- Boise
State University, Boise, Idaho 83725, United States of America
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6
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Gaur A, Balasubramanian S. Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:230-240. [PMID: 38150706 DOI: 10.1021/acs.langmuir.3c02431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.
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Affiliation(s)
- Anjali Gaur
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
| | - Sundaram Balasubramanian
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
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7
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Kumarasiri A, Yang P, Hore DK. Second-Order Nonlinear Optics as an Orientation-Independent Probe of Molecular Environments at Interfaces. J Phys Chem Lett 2023; 14:4449-4453. [PMID: 37146122 DOI: 10.1021/acs.jpclett.3c00771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Measurement techniques that probe the second-order susceptibility, such as second-harmonic and sum-frequency generation, are recognized for their ability to study environments with broken centrosymmetry. As a result, they serve as reporters of molecules at surfaces because the second-order susceptibility is often zero in the adjacent bulk media. Although the signals measured in such experiments carry unique information about the interfacial environment, the challenge is to disentangle properties related to the electronic structure as they are wrapped up in the orientation distribution. Over the past 30 years, this challenge has been turned into an opportunity, as many studies have sought to learn about the arrangement of molecules at surfaces. Here we demonstrate that the flipped case is possible, where fundamental properties of the interfacial environment can be extracted in a manner that is completely independent of, and therefore oblivious to, the orientation distribution. Using p-cyanophenol adsorbed at the air-water interface as an example, we illustrate that the cyano group polarizability varies less along the direction of the C-N bond when at the surface than when the same molecules are in the bulk aqueous phase.
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Affiliation(s)
- Aruna Kumarasiri
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Peter Yang
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Dennis K Hore
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
- Department of Computer Science, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
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8
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Korotkevich AA, Moll CJ, Versluis J, Bakker HJ. Molecular Orientation of Carboxylate Anions at the Water-Air Interface Studied with Heterodyne-Detected Vibrational Sum-Frequency Generation. J Phys Chem B 2023; 127:4544-4553. [PMID: 36917504 DOI: 10.1021/acs.jpcb.2c08992] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
The carboxylate anion group plays an important role in many (bio)chemical systems and polymeric materials. In this work, we study the orientation of carboxylate anions with various aliphatic and aromatic substituents at the water-air interface by probing the carboxylate stretch vibrations with heterodyne-detected vibrational sum-frequency generation spectroscopy in different polarization configurations. We find that carboxylate groups with small aliphatic substituents show a large tilt angle with respect to the surface normal and that this angle decreases with increasing size of the substituent. We further use the information about the orientation of the carboxylate group to determine the hyperpolarizability components of this group.
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Affiliation(s)
| | - Carolyn J Moll
- Ultrafast Spectroscopy, AMOLF, Science Park 104, Amsterdam 1098XG, Netherlands
| | - Jan Versluis
- Ultrafast Spectroscopy, AMOLF, Science Park 104, Amsterdam 1098XG, Netherlands
| | - Huib J Bakker
- Ultrafast Spectroscopy, AMOLF, Science Park 104, Amsterdam 1098XG, Netherlands
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9
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Wang Z, Pei Q, Wang M, Tan J, Ye S. Observing Nonpreferential Absorption of Linear and Cyclic Carbonate on the Silicon Electrode. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:2015-2021. [PMID: 36695809 DOI: 10.1021/acs.langmuir.2c03098] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Silicon is reported to be a promising anode material due to its high storage capacity and excellent energy conversion rate. Molecular-level insight into the interaction between silicon electrodes and electrolyte solutions is essential for understanding the formation of a stable solid electrolyte interphase (SEI), but it is yet to be explored. In this study, we apply femtosecond sum frequency generation vibrational spectroscopy to investigate the initial adsorption of various pure and mixed electrolyte molecules on the silicon anode surface by monitoring the SFG signals from the carbonyl group of electrolyte molecules. When the silicon comes in contact with a pure carbonate solution, the linear carbonates of diethyl carbonate and ethyl methyl carbonate adopt two conformations with opposite C═O orientations on the silicon interface while the cyclic carbonates of ethylene carbonate and propylene carbonate almost adopt one conformation with C═O bonds pointing toward the silicon electrode. When the silicon comes in contact with the mixed linear and cyclic carbonate solutions, the total SFG intensity from the mixed solutions is approximately 2∼5 times weaker than those of pure cyclic carbonates. The C═O bonds of cyclic carbonates point toward the silicon electrode, while the C═O bonds of linear carbonates face toward the bulk solution at the silicon/mixed solution interface. No preferential absorption behaviors of the linear and cyclic carbonate electrolytes on the silicon electrode are observed. Such findings may help to understand the mechanism by which the SEI formed on the silicon anode is unstable.
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Affiliation(s)
- Zhuo Wang
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui230026, China
| | - Quanbing Pei
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui230026, China
| | - Mengmeng Wang
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui230026, China
| | - Junjun Tan
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui230026, China
| | - Shuji Ye
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui230026, China
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10
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Yu CC, Seki T, Chiang KY, Tang F, Sun S, Bonn M, Nagata Y. Polarization-Dependent Heterodyne-Detected Sum-Frequency Generation Spectroscopy as a Tool to Explore Surface Molecular Orientation and Ångström-Scale Depth Profiling. J Phys Chem B 2022; 126:6113-6124. [PMID: 35849538 PMCID: PMC9421650 DOI: 10.1021/acs.jpcb.2c02178] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 07/01/2022] [Indexed: 11/28/2022]
Abstract
Sum-frequency generation (SFG) spectroscopy provides a unique optical probe for interfacial molecules with interface-specificity and molecular specificity. SFG measurements can be further carried out at different polarization combinations, but the target of the polarization-dependent SFG is conventionally limited to investigating the molecular orientation. Here, we explore the possibility of polarization-dependent SFG (PD-SFG) measurements with heterodyne detection (HD-PD-SFG). We stress that HD-PD-SFG enables accurate determination of the peak amplitude, a key factor of the PD-SFG data. Subsequently, we outline that HD-PD-SFG can be used not only for estimating the molecular orientation but also for investigating the interfacial dielectric profile and studying the depth profile of molecules. We further illustrate the variety of combined simulation and PD-SFG studies.
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Affiliation(s)
- Chun-Chieh Yu
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Takakazu Seki
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Kuo-Yang Chiang
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Fujie Tang
- Department
of Physics, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Shumei Sun
- Department
of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Mischa Bonn
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yuki Nagata
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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11
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de la Puente M, David R, Gomez A, Laage D. Acids at the Edge: Why Nitric and Formic Acid Dissociations at Air-Water Interfaces Depend on Depth and on Interface Specific Area. J Am Chem Soc 2022; 144:10524-10529. [PMID: 35658415 DOI: 10.1021/jacs.2c03099] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Whether the air-water interface decreases or increases the acidity of simple organic and inorganic acids compared to the bulk is critically important in a broad range of environmental and biochemical processes. However, a consensus has not yet been achieved on this key question. Here we use machine learning-based reactive molecular dynamics simulations to study the dissociation of paradigmatic nitric and formic acids at the air-water interface. We show that the local acidity profile across the interface is determined by changes in acid and conjugate base solvation and that the acidity decreases abruptly over a transition region of a few molecular layers. At the interface, both acids are weaker than in the bulk due to desolvation. In contrast, acidities below the interface reach a plateau and are all the stronger compared to those in the bulk as the surface to volume ratio of the aqueous phase is large, due to the growing impact of the stabilization of the released proton at the surface of the water. These results imply that the measured degree of dissociation sensitively depends on the experimental probing length and system size and suggest a molecular explanation for the contrasting experimental results. The aerosol size dependence of acidity has important consequences for atmospheric chemistry.
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Affiliation(s)
- Miguel de la Puente
- PASTEUR, Department of Chemistry, École Normale Supérieure-PSL, Sorbonne Université, CNRS, Paris 75005, France
| | - Rolf David
- PASTEUR, Department of Chemistry, École Normale Supérieure-PSL, Sorbonne Université, CNRS, Paris 75005, France
| | - Axel Gomez
- PASTEUR, Department of Chemistry, École Normale Supérieure-PSL, Sorbonne Université, CNRS, Paris 75005, France
| | - Damien Laage
- PASTEUR, Department of Chemistry, École Normale Supérieure-PSL, Sorbonne Université, CNRS, Paris 75005, France
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12
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Yu CC, Seki T, Wang Y, Bonn M, Nagata Y. Polarization-Dependent Sum-Frequency Generation Spectroscopy for Ångstrom-Scale Depth Profiling of Molecules at Interfaces. PHYSICAL REVIEW LETTERS 2022; 128:226001. [PMID: 35714258 DOI: 10.1103/physrevlett.128.226001] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/28/2022] [Accepted: 04/08/2022] [Indexed: 06/15/2023]
Abstract
The three-dimensional spatial distribution of molecules at soft matter interfaces is crucial for processes ranging from membrane biophysics to atmospheric chemistry. While several techniques can access surface composition, obtaining information on the depth distribution is challenging. We develop a noninvasive, polarization-resolved, surface-specific sum-frequency generation spectroscopy providing quantitative depth information. We demonstrate the technique on formic acid molecules at the air-water interface. With increasing molar fraction from 2.5% to 10%, the formic acid molecules shift, on average, ∼0.9 Å into the bulk. The consistency with the simulation data manifests that the technique allows for probing the Ångstrom-scale depth profile.
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Affiliation(s)
- Chun-Chieh Yu
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Takakazu Seki
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Yongkang Wang
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Mischa Bonn
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Yuki Nagata
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
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13
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Wang Z, Tan J, Yang Z, Luo Y, Ye S. Observing Two-Dimensional Spontaneous Reaction between a Silicon Electrode and a LiPF 6-Based Electrolyte In Situ and in Real Time. J Phys Chem Lett 2022; 13:3224-3229. [PMID: 35377653 DOI: 10.1021/acs.jpclett.2c00516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Two-dimensional spontaneous reactions between an electrode and an electrolyte are very important for the formation of a solid electrolyte interphase (SEI) but difficult to study because studying such reactions requires surface/interface sensitive techniques with sufficiently structural and temporal resolutions. In this study, we have applied femtosecond broadband sum-frequency generation vibrational spectroscopy (SFG-VS) to investigate the interaction between a silicon electrode and a LiPF6-based diethyl carbonate electrolyte solution in situ and in real time. We found that two kinds of diethyl carbonate species are present on the silicon surface and their C═O stretching aligns in opposite directions. Intrinsically spontaneous chemical reactions between silicon electrodes and a LiPF6 electrolyte solution are observed. The reactions generate silicon hydride and cause corrosion of the silicon electrodes. Coating of the silicon surface with a poly(vinyl alcohol) layer can effectively retard and attenuate these reactions. This work demonstrates that SFG-VS can provide a unique and powerful state-of-the-art tool for elucidating the molecular mechanisms of SEI formation.
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Affiliation(s)
- Zhuo Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Junjun Tan
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Zhe Yang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Yi Luo
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Shuji Ye
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
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