Chapter 9
Applications: Aqueous Interfaces
Abstract This chapter presents recent applications of the computational SFG
analysis for aqueous interfaces. Aqueous interfaces are relevant to a variety of
fields in chemistry and engineering, and have been extensively investigated by
SFG spectroscopy. Nevertheless, their hydrogen-bonding network and complicated
vibrational coupling hinder simple intuitive interpretation of the observed spectra.
The aid of MD simulation to analyze the complicated SFG spectra is actually
quite powerful. This chapter introduces the results of analysis for various aqueous
interfaces led by the author’s group and others, including water, ice, electrolyte
aqueous solutions, water-oil and water-membrane interfaces.
Keywords O–H stretching · Vibrational coupling · Interface thickness · Ion
segregation · Electric double layer
Water and aqueous interfaces have been extensively studied by the SFG spectroscopy, and computational analysis of their SFG spectra has been particularly
developed [32, 36, 61, 76, 96]. Water has its characteristic three-dimensional
network structure of hydrogen bonds, and the hydrogen-bond structure gives rise
to a number of peculiar properties of liquid water [3, 39]. Therefore, it is an
intriguing issue to understand the hydrogen-bonding structure of water surface, and
to reveal the structural difference from that of bulk water and its implications [44].
The interface structure is of fundamental importance to interfacial properties and
heterogeneous reactions at water surface.
One important advantage of applying the SFG spectroscopy to aqueous interfaces
is the availability of the O–H stretching vibrational band. The O–H stretching band
in 3000–3800 cm −1 region is fairly easy to measure technically by SFG spectroscopy, and its frequency and intensity are sensitive indicators of the hydrogenbond strength. Selective detection of the O–H stretching band of interfacial water
provides quite useful information on the interfacial structure of water.
On the other hand, SFG spectra of aqueous interfaces pose a challenge to
interpretation. The O–H stretching vibration of water involves various kinds of
vibrational couplings, both intramolecular and intermolecular, which complicate the
© Springer Nature Singapore Pte Ltd. 2018
A. Morita, Theory of Sum Frequency Generation Spectroscopy,
Lecture Notes in Chemistry 97, https://doi.org/10.1007/978-981-13-1607-4_9
219
Applications: Aqueous Interfaces
Abstract This chapter presents recent applications of the computational SFG
analysis for aqueous interfaces. Aqueous interfaces are relevant to a variety of
fields in chemistry and engineering, and have been extensively investigated by
SFG spectroscopy. Nevertheless, their hydrogen-bonding network and complicated
vibrational coupling hinder simple intuitive interpretation of the observed spectra.
The aid of MD simulation to analyze the complicated SFG spectra is actually
quite powerful. This chapter introduces the results of analysis for various aqueous
interfaces led by the author’s group and others, including water, ice, electrolyte
aqueous solutions, water-oil and water-membrane interfaces.
Keywords O–H stretching · Vibrational coupling · Interface thickness · Ion
segregation · Electric double layer
Water and aqueous interfaces have been extensively studied by the SFG spectroscopy, and computational analysis of their SFG spectra has been particularly
developed [32, 36, 61, 76, 96]. Water has its characteristic three-dimensional
network structure of hydrogen bonds, and the hydrogen-bond structure gives rise
to a number of peculiar properties of liquid water [3, 39]. Therefore, it is an
intriguing issue to understand the hydrogen-bonding structure of water surface, and
to reveal the structural difference from that of bulk water and its implications [44].
The interface structure is of fundamental importance to interfacial properties and
heterogeneous reactions at water surface.
One important advantage of applying the SFG spectroscopy to aqueous interfaces
is the availability of the O–H stretching vibrational band. The O–H stretching band
in 3000–3800 cm −1 region is fairly easy to measure technically by SFG spectroscopy, and its frequency and intensity are sensitive indicators of the hydrogenbond strength. Selective detection of the O–H stretching band of interfacial water
provides quite useful information on the interfacial structure of water.
On the other hand, SFG spectra of aqueous interfaces pose a challenge to
interpretation. The O–H stretching vibration of water involves various kinds of
vibrational couplings, both intramolecular and intermolecular, which complicate the
© Springer Nature Singapore Pte Ltd. 2018
A. Morita, Theory of Sum Frequency Generation Spectroscopy,
Lecture Notes in Chemistry 97, https://doi.org/10.1007/978-981-13-1607-4_9
219