Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Jubb, Aaron M.; Wei, Hua; Allen, Heather C.

doi:10.1146/annurev-physchem-032511-143811

Cited by 146 publications

(271 citation statements)

References 144 publications

(240 reference statements)

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“…SHG and SFG are described in detail in a number of standard textbooks, 1,2 and the study of adsorbates at interfaces using SHG and SFG has been the focus of a number of excellent reviews. [3][4][5][6][7] Unfortunately, the non-linear signal is often very weak and this is a particular problem when the interfacial concentration of the adsorbate species is small. This situation generally arises for time-resolved measurements in which a pump pulse only excites a small fraction of adsorbates to induce the process of interest that is subsequently probed by SHG a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved phase-sensitive second harmonic generation spectroscopy

Nowakowski

Woods

Bain

et al. 2015

The Journal of Chemical Physics

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A methodology based on time-resolved, phase-sensitive second harmonic generation (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator generated at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times. C 2015 AIP Publishing LLC.[http://dx

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Section: Introductionmentioning

confidence: 99%

Time-resolved phase-sensitive second harmonic generation spectroscopy

Nowakowski

Woods

Bain

et al. 2015

The Journal of Chemical Physics

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“…Accordingly, many experimental and theoretical efforts have been aimed at elucidating the ion distribution at the interface of water. For the ubiquitous sodium halide salts, it has been established both through experiments 4,[6][7][8][9][10] and molecular dynamics simulations [4][5][6][7][9][10][11][12] that, for example the Cl À ion has a weak, whereas the I À ion has a strong surface propensity. Moreover, a distinct spatial separation has been observed for ions at the water interface, with anions residing in the outmost surface layer, while cations occupying the subsurface region 4,[13][14][15][16][17] .…”

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confidence: 99%

Extreme surface propensity of halide ions in water

et al. 2014

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Water possesses an extremely high polarity, making it a unique solvent for salts. Indeed, aqueous electrolyte solutions are ubiquitous in the atmosphere, biology, energy applications and industrial processes. For many processes, chemical reactions at the water surface are rate determining, and the nature and concentration of the surface-bound electrolytes are of paramount importance, as they determine the water structure and thereby surface reactivity. Here we investigate the dynamics of water molecules at the surface of sodium chloride and sodium iodide solutions, using surface-specific femtosecond vibrational spectroscopy. We quantify the interfacial ion density through the reduced energy transfer rates between water molecules resulting from the lowered effective interfacial density of water molecules, as water is displaced by surface active ions. Our results reveal remarkably high surface propensities for halogenic anions, higher for iodide than for chloride ions, corresponding to surface ion concentrations several times that of the bulk.

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“…Because of its surface sensitivity, vibrational sum-frequency generation (SFG) spectroscopy (11,12) has become one of the most powerful experimental techniques for the study of interfaces, including the one separating liquid water and its vapor (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). In a vibrational SFG experiment, infrared (IR) and visible laser pulses are incident on the interface, and the signal is detected at the sum of the frequencies of these incoming beams.…”

mentioning

confidence: 99%

Slow hydrogen-bond switching dynamics at the water surface revealed by theoretical two-dimensional sum-frequency spectroscopy

Gruenbaum

Skinner

2013

Proc. Natl. Acad. Sci. U.S.A.

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Using our newly developed explicit three-body (E3B) water model, we simulate the surface of liquid water. We find that the timescale for hydrogen-bond switching dynamics at the surface is about three times slower than that in the bulk. In contrast, with this model rotational dynamics are slightly faster at the surface than in the bulk. We consider vibrational two-dimensional (2D) sum-frequency generation (2DSFG) spectroscopy as a technique for observing hydrogen-bond rearrangement dynamics at the water surface. We calculate the nonlinear susceptibility for this spectroscopy for two different polarization conditions, and in each case we see the appearance of cross-peaks on the timescale of a few picoseconds, signaling hydrogen-bond rearrangement on this timescale. We thus conclude that this 2D spectroscopy will be an excellent experimental technique for observing slow hydrogen-bond switching dynamics at the water surface. Interfaces play important roles in many disciplines of science. The water liquid/vapor interface, for example, is of great interest in chemistry, biology, and earth science and is an important model system for water in a heterogeneous environment. Of particular interest is understanding the extent to which the structure and dynamics, and ultimately reactivity, of water at the interface differ from those in the bulk. For example, how does the distribution of hydrogen bonds differ between interfacial and bulk water? How anisotropic is the orientation of the water molecules at the interface? In terms of dynamics, how do the diffusion constant, rotational relaxation time, and hydrogen-bond rearrangement time vary as the interface is approached? One can also consider vibrational dynamics processes such as energy relaxation and transfer.One important technique for addressing these questions is computer simulation. Models used in these calculations for the water surface range from rigid, fixed-point-charge two-body models (1-3), to fluctuating charge or polarizable models (4, 5), to ab initio molecular dynamics calculations (6-10). Regarding static properties, for example, some effort has been expended toward understanding what fraction of H atoms in the surface layer are hydrogen bonded, and what fraction of molecules do not donate any hydrogen bonds (nondonors or "acceptor-only" molecules) (6, 9). In terms of dynamics, it is generally found that diffusion is faster at the interface than in the bulk (1, 4, 10), and rotational relaxation is also faster (3,6,7,10). On the other hand, two studies with fixed-charge two-body models show that hydrogenbond rearrangement is slower at the interface (2, 3), whereas one study with a fluctuating-charge model shows that hydrogen-bond rearrangement is faster (5). In this latter study the authors conclude that this is generally true for polarizable models.Because of its surface sensitivity, vibrational sum-frequency generation (SFG) spectroscopy (11, 12) has become one of the most powerful experimental techniques for the study of interfaces, including the one separa...

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Environmental Chemistry at Vapor/Water Interfaces: Insights from Vibrational Sum Frequency Generation Spectroscopy

Cited by 146 publications

References 144 publications

Time-resolved phase-sensitive second harmonic generation spectroscopy

Time-resolved phase-sensitive second harmonic generation spectroscopy

Extreme surface propensity of halide ions in water

Slow hydrogen-bond switching dynamics at the water surface revealed by theoretical two-dimensional sum-frequency spectroscopy

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