Adsorption of heptane–toluene binary mixtures on a hydrophobic polymer surface

Ramsay, Margo; Beutier, Clémentine; McGarvey, G.B.; Hore, Dennis K.

doi:10.1063/1.5066555

Cited by 10 publications

(7 citation statements)

References 57 publications

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“…Hence, in interpreting the line shapes of VSFG spectra, the Fresnel factors were usually estimated under the assumption that they were constants in the frequency range in question. However, one should also consider the fact that the Fresnel factors may involve the frequency dependence as well. ,, Since the Fresnel factor primarily reflects the refractive indices of the media, highly dispersive media result in frequency-dependent Fresnel factors. Thus, in order to extract pure χ (2) (ω IR ) spectra from the observed VSFG intensity, it is important to answer the following questions: (a) How does the frequency dependence of Fresnel factors influence the band shape of VSFG spectra?…”

Section: Introductionmentioning

confidence: 99%

Effect of Frequency-Dependent Fresnel Factor on the Vibrational Sum Frequency Generation Spectra for Liquid/Solid Interfaces

et al. 2019

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Vibrational sum frequency generation (VSFG) spectroscopy is a powerful tool for selective probing of interfaces based on second-order nonlinear optics. The line shapes of observed VSFG spectra are governed by second-order nonlinear susceptibility as well as Fresnel factors for constituent light fields. Hence, determination of the second-order nonlinear susceptibility requires exact knowledge about the Fresnel factors for the light fields. However, the latter has been less examined than the former for interpretation of VSFG spectra to date and is sometimes hard to calculate due to a lack of optical constants, especially in the infrared regions. The present work employs ATR-IR measurements and model fitting to determine the complex refractive indices of organic solvents and clarifies the effect of the Fresnel factor on the line shape analysis of VSFG spectra. As an example, we determine the complex refractive indices of organic carbonates, which are typical solvents for lithium-ion battery, in the CO and CH stretch vibration regions, and then examined the effect of frequency-dependent Fresnel factor on the VSFG spectra of electrode/carbonate as well as air/carbonate interfaces by model calculations. The Fresnel factor in the CO stretch region has considerable dispersion due to the large extinction coefficient, which strongly influences the line shape of VSFG spectra at LiCoO2/carbonate interfaces, especially for the SPS polarization combination. On the contrary, the frequency-dependent Fresnel factor in the CH stretch region has little effect on the line shape of the band. The present systematic study of Fresnel factor revealed that the effect of Fresnel factor on the VSFG line shape becomes significant when (i) the frequency dependence of complex refractive index is large in the range of the band and (ii) nonresonant amplitude of nonlinear susceptibility is considerable relative to the resonant amplitude.

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Section: Introductionmentioning

confidence: 99%

Effect of Frequency-Dependent Fresnel Factor on the Vibrational Sum Frequency Generation Spectra for Liquid/Solid Interfaces

et al. 2019

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“…However, in experiments that seek to modulate the coherence by changing the angle of incidence, it is of the utmost importance to consider the angle dependence of the magnitude and phase of these factors. This is especially true for internal reflection geometries where the local field correction factors are complex valued above the critical angle even when the absorption coefficient is negligible. , It must be carefully verified that the observed angle dependence is beyond that attributed to these factors, and the true angle dependence of χ total (2) is then available for analysis.…”

Section: Results and Discussionmentioning

confidence: 99%

“…This is especially true for internal reflection geometries where the local field correction factors are complex valued above the critical angle even when the absorption coefficient is negligible. 54,55 It must be carefully verified that the observed angle dependence is beyond that attributed to these factors, and the true angle dependence of χ total (2) is then available for analysis. The basis of the methods is to change the coherence length and consequently Δk z in the g 3 term without changing other parameters.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Determining the Surface Potential of Charged Aqueous Interfaces Using Nonlinear Optical Methods

2021

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Second-order nonlinear optical techniques have recently been established as sensitive probes of charged interfaces through the nonlinear susceptibility of water and provide an attractive route to elucidate the surface potential. We discuss methods that have been proposed using electronic second-harmonic generation and vibrational sum-frequency generation. A detailed comparison is provided, using a unified notation and including a discussion of the assumptions that are either convenient or necessary in order to arrive at the surface potential. We then illustrate that, when using the full solution of the Poisson–Boltzmann equation that is applicable to a wide range of surface potentials, several benefits may be realized. The first is that, when using off-resonance phase measurements, the surface potential can be determined from the phase alone, without any additional information or calibrated intensity schemes. Next, we illustrate a scheme for surface potential measurement using intensity-only data off-resonance by changing the angle of incidence. Finally, we discuss the possibility of measurements that target the vibrational resonance with water and illustrate how the surface potential can be isolated from such data.

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“…In addition to detecting surface-adsorbed species by observing specific vibrational resonances, SFG spectroscopy can be used to provide information on the structure of molecules at the interface by the analysis of mode amplitudes obtained with at least two different beam polarizations. For experiments in which only a single polarization combination is accessible or practical, or there are congested spectral regions where fitting to isolate the behavior of individual vibrational modes is not robust, two-dimensional correlation analysis (2DCOS) can be informative. − Developed by Noda, the technique of generalized 2DCOS enables the correlation between different frequency components in vibrational spectra collected with respect to an external variable to be analyzed in terms of synchronous and asynchronous changes. − We have previously illustrated how 2DCOS can be applied to SFG intensity data and may be used to provide structural insight in a variety of applications. − We now demonstrate an additional merit of a combination of homo- and heterospectral 2DCOS when SFG spectra are combined with bulk infrared (IR) and/or Raman spectra to determine the surface preference.…”

Section: Introductionmentioning

confidence: 99%

Determination of Surface Preference Using Heterospectral Surface–Bulk Correlation Spectroscopy

2020

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We outline a method by which the surface preference of a species in a multicomponent mixture may be obtained using surface-specific visible–infrared sum frequency generation (SFG) spectroscopy combined with bulk infrared absorption and/or Raman data. In general, the problem is complicated by the fact that the SFG signal is a function of both the surface coverage and the structure of the molecules. Two-dimensional correlation analysis can be used to reveal which spectral features are changing synchronously, that is, in phase with each other, and which ones are evolving in a manner that is phase-shifted by 90° (asynchronous correlation) as a function of the bulk composition. We provide a framework for determining the surface preference from the correlations between the vibrational modes in the SFG spectra and between the modes from SFG and bulk infrared and/or Raman spectra. When compared to the equivalent analysis performed using the SFG spectra alone, this method can be used with the data obtained using a single-beam polarization and in congested spectral regions where fitting to isolate the behavior of individual vibrational modes is not robust.

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Adsorption of heptane–toluene binary mixtures on a hydrophobic polymer surface

Cited by 10 publications

References 57 publications

Effect of Frequency-Dependent Fresnel Factor on the Vibrational Sum Frequency Generation Spectra for Liquid/Solid Interfaces

Effect of Frequency-Dependent Fresnel Factor on the Vibrational Sum Frequency Generation Spectra for Liquid/Solid Interfaces

Determining the Surface Potential of Charged Aqueous Interfaces Using Nonlinear Optical Methods

Determination of Surface Preference Using Heterospectral Surface–Bulk Correlation Spectroscopy

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