Sum frequency generation spectroscopy of the aqueous interface: Ionic and soluble molecular solutions

Shultz, Mary Jane; Schnitzer, Cheryl; Simonelli, Danielle; Baldelli, Steve

doi:10.1080/014423500229882

Cited by 273 publications

(357 citation statements)

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“…the dynamics of rotation in the interfacial plane differ from the out-of-plane orientational motions. [15][16][17][18] Second harmonic generation (SHG) and sum frequency generation (SFG), [11][12][13][14][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] as second-order spectroscopies, are interface specific, including buried interfaces that are accessible to light. Second harmonic generation (SHG) depends primarily on the electronic properties of the interfacial molecules whereas SFG is sensitive to molecular vibrations when one of the incident beams is in the infrared.…”

Section: Introductionmentioning

confidence: 99%

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

et al. 2008

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The first time-resolved experiments in which interfacial molecules are pumped to excited electronic states and probed by vibrational sum frequency generation (SFG) are reported. This method was used to measure the out-of-plane rotation dynamics, i.e. time dependent changes in the polar angle, of a vibrational chromophore of an interfacial molecule. The chromophore is the carbonyl group, the rotation observed is that of the sCdO bond axis, with respect to the interfacial normal, and the interfacial molecule is coumarin 314 (C314) at the air/water interface. The orientational relaxation time was found to be 220 ( 20 ps, which is much faster than the orientational relaxation time of the permanent dipole moment axis of C314 at the same interface, as obtained from pump-second harmonic probe experiments. Possible effects on the rotation of the sCdO bond axis due to the carbonyl group hydrogen bonding with interfacial water are discussed. From the measured equilibrium orientation of the permanent dipole moment axis and the carbonyl axis, and knowledge of their relative orientation in the molecule, the absolute orientation of C314 at the air/water interface is obtained.

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Section: Introductionmentioning

confidence: 99%

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

et al. 2008

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“…2,3,[5][6][7][8] Orientation measurements of chemical groups at interfaces and surfaces were realized soon after the SFG technique was applied to the study of interfaces and surfaces. 9 Recently, the orientational angle with respect to the surface normal and the twist angle relative to the plane comprising the surface normal and the symmetry axis of the isopropyl headgroup of a leucine molecule at the air/water interface was measured.…”

Section: Introductionmentioning

confidence: 99%

Absolute Orientation of Molecules at Interfaces

2006

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A method to determine the absolute orientation of molecules at liquid interfaces by sum frequency generation (SFG) is reported. It is based on measurements of the orientations of two nonparallel vibrationally active chromophores in the molecule of interest combined with a rotation matrix formulation to obtain the absolute molecular orientation. We chose m-tolunitrile, a planar molecule adsorbed to the air/water interface, as a proof-of-method experiment. Quantitative analysis of different polarization sum frequency intensities facilitate unique peak assignments of the methyl and nitrile groups of m-tolunitrile. The SFG analysis of the measurement yields a nitrile group tilting at 53°to the surface normal, and the C 3 axis of the methyl group is almost upright at 23°with respect to the surface normal. Using a rotation matrix formulation, we found that the angle between the surface plane and the m-tolunitrile molecular plane is 70°.

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“…Moreover, it can be considered unlikely that these porphyrine-carrying molecules exhibit the orientation preference required for SFG activity. Other NH containing compounds such as amino acids, peptides or amino sugars [Mermut et al, 2006;Aluwihare and Meador, 2008] are expected to yield signal around 3300 cm −1 [Shultz et al, 2000]. Consequently, (1) the presence of additional OH group containing compounds and/or (2) confined water molecules or water clusters residing in dense organic monolayers may serve as more probable explanations.…”

Section: Surfactant Effectsmentioning

confidence: 99%

Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

Laß¹,

Friedrichs²

2011

J. Geophys. Res.

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Natural nanolayers originating from sea surface and subsurface water samples collected in the Baltic Sea have been investigated using surface‐sensitive vibrational sum frequency generation (VSFG) spectroscopy. Distinct spectral signatures of CH and OH bond stretch vibrations have been detected at wavenumbers ranging from 2700 to 3900 cm−1. Measured water‐air interface spectra as well as observed signal intensity trends are discussed in terms of composition and structure of the natural organic nanolayer. Reasoning was based on the comparison with reference spectra, spectral trends inferred from previous VSFG studies, reported average composition of dissolved organic matter in seawater, and simplified assumption that surfactants can be classified as soluble (wet) and insoluble (dry) surfactants. Wet surfactants have been found to be dominant, and often lipid‐like compounds form a very dense surfactant nanolayer. Supported by comparison spectra of xanthan gum solutions, the observed VSFG spectral signatures were tentatively assigned to lipopolysaccharides or other lipid‐like compounds embedded in colloidal matrices of polymeric material. In addition, VSFG spectra of a polluted harbor water sample and a water sample covered with diesel oil are reported.

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Sum frequency generation spectroscopy of the aqueous interface: Ionic and soluble molecular solutions

Cited by 273 publications

References 0 publications

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

Absolute Orientation of Molecules at Interfaces

Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

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