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Ramos TN, Champagne B. Disentangling the molecular polarizability and first hyperpolarizability of methanol-air interfaces. Phys Chem Chem Phys 2024; 26:8658-8669. [PMID: 38437015 DOI: 10.1039/d4cp00043a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
Liquid-air interfaces have extensive implications in different areas of interest because the dynamical processes at the interface can be different from those in bulk. Thus, its characterization, understanding, and control may be pivotal in advancing discoveries. However, characterizing the interface requires special and selective tools to avoid signals from the bulk region. This surface specificity and versatility is achieved by using the second harmonic generation (SHG) responses. This study adopts multiscale simulation methods to evaluate the surface SHG responses of methanol-air interfaces with submonolayer resolution tackled by sequentially using classical molecular dynamics simulations under different temperatures and then employing quantum chemistry methods to compute the molecular first hyperpolarizabilities (β). This approach ensures the configurational diversity required to evaluate the average β values. The main achievements are (i) a quasi-absence of surface sensitivity of the mean polarizability 〈α〉 with values about 2% larger than those obtained in bulk, (ii) conversely, smooth variations on the polarizability anisotropy Δα are observed up to the fourth molecular layer at around 20 Å from the interface, and (iii) narrow interfacial effects on the SHG responses, β(-2ω;ω,ω), which are limited to the first molecular layer (∼3.0 Å) and characterized by a high contrast in the βZZZ(-2ω;ω,ω) tensor component between the first and the subsequent layers. Similar trends are obtained at different temperatures or when increasing the number of methanol molecules treated at the quantum chemistry level, indicating the robustness of the approach for describing the dipolar molecular responses of air-liquid interfaces.
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Affiliation(s)
- Tárcius N Ramos
- Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, rue de Bruxelles, 61, B-5000 Namur, Belgium.
| | - Benoît Champagne
- Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, rue de Bruxelles, 61, B-5000 Namur, Belgium.
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Le Breton G, Bonhomme O, Benichou E, Loison C. Liquid Water: When Hyperpolarizability Fluctuations Boost and Reshape the Second Harmonic Scattering Intensities. J Phys Chem Lett 2023; 14:4158-4163. [PMID: 37104636 DOI: 10.1021/acs.jpclett.3c00546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Second harmonic scattering (SHS) is a method of choice to investigate the molecular structure of liquids. While a clear interpretation of SHS intensity exists for diluted solutions of dyes, the scattering due to solvents remains difficult to interpret quantitatively. Here, we report a quantum mechanics/molecular mechanics (QM/MM) approach to model the polarization-resolved SHS intensity of liquid water, quantifying different contributions to the signal. We point out that the molecular hyperpolarizability fluctuations and correlations cannot be neglected. The intermolecular orientational and hyperpolarizability correlations up to the third solvation layer strongly increase the scattering intensities and modulate the polarization-resolved oscillation that is predicted here by QM/MM without fitting parameters. Our approach can be generalized to other pure liquids to provide a quantitative interpretation of SHS intensities in terms of short-range molecular ordering.
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Affiliation(s)
- Guillaume Le Breton
- Univ Lyon, Univ Claude Bernard Lyon1, CNRS, Light and Matter Institute, F-69622 Villeurbanne, France
| | - Oriane Bonhomme
- Univ Lyon, Univ Claude Bernard Lyon1, CNRS, Light and Matter Institute, F-69622 Villeurbanne, France
| | - Emmanuel Benichou
- Univ Lyon, Univ Claude Bernard Lyon1, CNRS, Light and Matter Institute, F-69622 Villeurbanne, France
| | - Claire Loison
- Univ Lyon, Univ Claude Bernard Lyon1, CNRS, Light and Matter Institute, F-69622 Villeurbanne, France
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Jami L, Zemb T, Casas J, Dufrêche JF. Individual adsorption of low volatility pheromones: Amphiphilic molecules on a clean water-air interface. J Chem Phys 2022; 157:094708. [PMID: 36075737 DOI: 10.1063/5.0110264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Environmental conditions can alter olfactory scent and chemical communication among biological species. In particular, odorant molecules interact with aerosols. Thermodynamics variables governing the adsorption from air to water surface of bombykol, the most studied pheromone, and of three derivative molecules, bombykal, bombykoic acid, and bombykyle acetate, are computed by steered and un-biased molecular dynamics in order to compare the role of their polar head group on adsorption on aqueous aerosols. When adsorbed, the molecule center of mass stands at about 1.2 Å from the interface and oscillates on the same length scale, trapped in an energy well. Gibbs energy of adsorption and desorption time of bombykol are found to be 9.2 kBT and 59 µs, respectively. The following ordering between the molecules is observed, reading from the more to the least adsorbed: bombykoic acid > bombykol > bombykoic acetate > bombykal. It originates from a complex interplay of entropy and enthalpy. The entropy and enthalpy of adsorption are discussed in the light of structural arrangement, H-bonding, and hydrophilic tail positioning of the molecules at the interface. Our results show that, when dispersed in the air, pheromones adsorb on aqueous aerosols. However, the individual residence time is quite short on pure water surfaces. Aerosols can, therefore, only have a decisive influence on chemical communication through collective effects or through their chemical composition that is generally more complex than that of a pure water surface.
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Affiliation(s)
- L Jami
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS-Université de Tours, Tours, France
| | - T Zemb
- ICSM, CEA, CNRS, ENSCM, Univ. Montpellier, Marcoule, France
| | - J Casas
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS-Université de Tours, Tours, France
| | - J-F Dufrêche
- ICSM, CEA, CNRS, ENSCM, Univ. Montpellier, Marcoule, France
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Ramos TN, Champagne B. Investigation of the Second Harmonic Generation at the Water-Vacuum Interface by Using Multi-Scale Modeling Methods. Chemistry 2022; 12:e202200045. [PMID: 35950561 PMCID: PMC9806952 DOI: 10.1002/open.202200045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/16/2022] [Indexed: 01/28/2023]
Abstract
The Sequential Quantum Mechanics/Molecular Mechanics scheme has been enacted to perform a systematic investigation of the polarizability (α) and first hyperpolarizability (β) responses at the water-vacuum interface. After performing classical molecular dynamics simulations to provide snapshots of the structures, quantum chemistry calculations of the linear and nonlinear optical responses have been performed for clusters of five water molecules at the time-dependent DFT level in combination with different embedding schemes, ranging from point charges to polarizable point charges, with and without local field effects. When going from the bulk to the interface, the main observations of these calculations encompass i) a modest increase of the average polarizability but an increase by about a factor of two of its anisotropy, ii) an increase by about 20 % of the βHRS response, accompanied by a small increase of its depolarization ratio, and iii) a net increase of the component of the β tensor normal to the interface (βzzz ) as well as of β// . Globally, the interfacial effects on β are localized at the first molecular layer while they are observed up to the fourth molecular layer on α.
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Affiliation(s)
- Tárcius N. Ramos
- Laboratory of Theoretical ChemistryNamur Institute of Structured Matter (NISM)University of NamurRue de Bruxelles, 61B-5000NamurBelgium
| | - Benoît Champagne
- Laboratory of Theoretical ChemistryNamur Institute of Structured Matter (NISM)University of NamurRue de Bruxelles, 61B-5000NamurBelgium
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Foucaud Y, Dufrêche JF, Siboulet B, Duvail M, Jonchère A, Diat O, Vuilleumier R. Why local and non-local terms are essential for second harmonic generation simulation? Phys Chem Chem Phys 2022; 24:12961-12973. [PMID: 35580631 DOI: 10.1039/d1cp05437f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Second Harmonic Generation (SHG) today represents one of the most powerful techniques to selectively probe all types of interfaces. However, the origin of the SHG signal at a molecular level is still debated since the local dipole contribution, which is strongly correlated to the molecular orientation can be counterbalanced by non-local quadrupole contributions. Here, we propose a method to simulate the SHG signal of a model water/air interface from the molecular response of each contribution. This method includes both local and non-local terms, which are represented, respectively, by the dependency of the polarisability and hyperpolarisability upon the chemical environment of the molecule and by the bulk quadrupole response. The importance of both terms for the sound simulation of the SHG signals and their interpretation is assessed. We demonstrate that the sole dipole term is unable to simulate a SHG signal, even if the dependency of the hyperpolarisability on the local environment is considered. The inclusion of the bulk quadrupole contribution, which largely dominates the dipole contribution, is essential to predict the SHG response, although the accuracy of the prediction is increased when the dependency upon the local environment is considered.
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Affiliation(s)
- Yann Foucaud
- ICSM, Univ Montpellier, CEA, CNRS, ENSCM, Marcoule, France.
| | | | | | - Magali Duvail
- ICSM, Univ Montpellier, CEA, CNRS, ENSCM, Marcoule, France.
| | - Alban Jonchère
- ICSM, Univ Montpellier, CEA, CNRS, ENSCM, Marcoule, France.
| | - Olivier Diat
- ICSM, Univ Montpellier, CEA, CNRS, ENSCM, Marcoule, France.
| | - Rodolphe Vuilleumier
- PASTEUR, Département de Chimie, Ecole normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
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Le Breton G, Bonhomme O, Benichou E, Loison C. First Hyperpolarizability of Water in Bulk Liquid Phase: Long-Range Electrostatic Effects Included via the Second Hyperpolarizability. Phys Chem Chem Phys 2022; 24:19463-19472. [DOI: 10.1039/d2cp00803c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The molecular first hyperpolarizability β contributes to second-order optical non-linear signals collected from molecular liquids. For the Second Harmonic Generation (SHG) response, the first hyperpolarizability β (2ω,ω,ω) often depends on...
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