Ordering of Interfacial Water Molecules at the Charged Air/Water Interface Observed by Vibrational Sum Frequency Generation

Gragson, D. E.; McCarty, B. M.; Richmond, Geraldine L.

doi:10.1021/ja962277y

Cited by 270 publications

(417 citation statements)

References 27 publications

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“…The peak assignments are consistent with previously assigned vibrational modes of SDS obtained using a scanning SFG system. 29 Furthermore, a broad peak is observed at ~3100 cm -1 and is attributed to the water symmetric stretching vibrational mode from the water molecules at the surface of the SDS solution.…”

Section: Resultsmentioning

confidence: 99%

Broadband Vibrational Sum Frequency Generation Spectroscopy of a Liquid Surface

Hommel

Allen

2001

ANAL. SCI.

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Atmospheric aerosol surface chemistry, polar stratospheric cloud surface chemistry, and soil-water interfacial chemistry are examples of environmentally relevant interfaces that are not well understood at the molecular level. In light of the need to understand the molecular-level details of one of these interfacial systems, we demonstrate here advances in the field of surface spectroscopy, in particular, broad-bandwidth sum frequency generation (BBSFG) spectroscopy.Broad-bandwidth sum frequency generation technology is gaining recognition for studying solid-surface structure and chemistry. 6-13 However, acquiring BBSFG spectra from liquid surfaces has been more elusive due to the inherently small nonlinear response from many liquid surfaces. Nevertheless, we show here, for the first time, BBSFG spectra obtained from a liquid surface.There have been a significant number of surface spectra published using scanning SFG instruments from liquid surfaces; however, until now a BBSFG spectrum from a liquid surface had not been obtained. A new double-amplifier design, which is explained in a previously published paper 14 was used for the acquisition of these BBSFG spectra. The data presented in this paper show that BBSFG can now be successfully utilized to probe the vibrational modes of molecules at liquid surfaces. We also demonstrate the time-resolved capability of this BBSFG system to acquire data in as few as 500 ms.Visible-infrared BBSFG spectroscopy provides molecularlevel information about molecular species at an interface in the form of polarization-dependent vibrational data from the surface molecules. The strength of BBSFG spectroscopy lies in its inherent ability to attain a full surface spectrum within one pulse of the laser system, thus potentially allowing temporally resolved spectroscopic data from reactions occurring at an interface.Vibrational sum frequency generation spectroscopy experiments have mainly been performed using scanning SFG instruments with pulse-widths in the ps (picosecond) [15][16][17][18][19] or ns (nanosecond) 20-23 time regime that produce relatively narrow spectral bandwidths. In a scanning SFG system the nonlinear crystals used to convert a portion of the visible wavelength beam to an infrared beam are angle tuned. The angle tuning causes small directional changes in the beam path, which can affect the spatial overlap of the two incident beams at the sample surface. This can compromise the spectral reproducibility and the shape of the scanning SFG spectrum. Scanning SFG systems, by the nature of the system, are primarily used on equilibrium or static interfaces. Although scanning sum frequency instruments are still considered stateof-the-art for surface spectroscopic technology, a new generation of broad-bandwidth (non-scanning) SFG instruments have taken center-stage because of their ability to capture a full spectrum within one pulse of the laser, thereby providing timeresolved surface data in addition to static or equilibrium surface data.Although sum frequency generation has b...

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Section: Resultsmentioning

confidence: 99%

Broadband Vibrational Sum Frequency Generation Spectroscopy of a Liquid Surface

Hommel

Allen

2001

ANAL. SCI.

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“…Due to a structural alignment of the water molecules with respect to the interface, polar or charged monolayers exert a pronounced influence on the spectral signature of the OH network (Gragson et al 1997;Richmond 2001). This can be seen from the observed OH network signal enhancement in case of the DPPC monolayer.…”

Section: Assessmentmentioning

confidence: 99%

Vibrational sum‐frequency generation as a probe for composition, chemical reactivity, and film formation dynamics of the sea surface nanolayer

Laβ

Kleber

Friedrichs

2010

Limnology & Ocean Methods

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Vibrational Sum Frequency Generation (VSFG) is a surface sensitive nonlinear laser spectroscopic technique, which has been widely used in physics and physical chemistry to investigate interface processes and heterogeneous chemistry. As the technique advances from basic to applied research, we have assessed its suitability for investigations of natural air-water interfaces, which are typically covered with an organic nanolayer. Vibrational spectra of natural sea surface nanolayer samples are presented. Strong signals attributable to the alkyl chains of lipids and indications for more or less soluble carbohydrate material have been found. Furthermore, the use of VSFG spectroscopy as a time-resolved detection tool for monitoring surface layer formation and its reactive decay is demonstrated. Ozone-induced film oxidation served as an example. We successfully applied VSFG to characterize the efficiency of a surface water screen sampler as well. Overall, VSFG spectroscopy turns out to be a versatile tool that can provide valuable information about composition, structure, chemical reactivity, and film formation dynamics of the sea surface nanolayer.*Corresponding author: E-mail: friedrichs@phc.uni-kiel.de AcknowledgmentsWe are indebted to the people from the Boknis Eck project at IFM-GEOMAR for the opportunity to take samples during their sample cruises, and to captain and crew of the R/V Littorina for their support during the cruises. Thanks to Friedrich Temps and Doug Wallace for helpful discussions. Financial support by the German Science Foundation (DFG -EC 80) in the framework of the cluster of excellence The Future Ocean is gratefully acknowledged.

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“…BBSFG) has application to the molecular level understanding of time-resolved interfacial processes. 1 SFG is becoming widely used as an analytical technique to understand a variety of interfaces [2][3][4][5][6][7][8][9][10] since it is surface-selective, provides spectroscopic data, i.e. molecular level information, and it can be utilized in most pressure regimes, e.g.…”

Section: Introductionmentioning

confidence: 99%

Broadband Sum Frequency Generation with Two Regenerative Amplifiers: Temporal Overlap of Femtosecond and Picosecond Light Pulses

Hommel

Allen

2001

ANAL. SCI.

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Sum frequency generation (SFG) spectroscopy is a valuable tool for studying interfaces such that the boundary between two adjoining phases can be probed with minimal interference from the adjacent bulk material. More recently, broadbandwidth sum frequency generation (BBSFG) techniques are being explored. This technique using IR broad-bandwidth fs pulses overlapped with narrow-bandwidth ps pulses to obtain BBSFG spectra is described. In the BBSFG system design presented here, the fs pulse and the ps pulse that are generated in separate regenerative amplifiers are overlapped temporally. This temporal overlap process is discussed. In addition, images of the sum frequency response demonstrate its viability. The new approach in experimental design described here for this emerging technology, BBSFG, has application for studying time-dependent processes at interfaces that inherently produce low SFG signal levels such as airaqueous interfaces.

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Ordering of Interfacial Water Molecules at the Charged Air/Water Interface Observed by Vibrational Sum Frequency Generation

Cited by 270 publications

References 27 publications

Broadband Vibrational Sum Frequency Generation Spectroscopy of a Liquid Surface

Broadband Vibrational Sum Frequency Generation Spectroscopy of a Liquid Surface

Vibrational sum‐frequency generation as a probe for composition, chemical reactivity, and film formation dynamics of the sea surface nanolayer

Broadband Sum Frequency Generation with Two Regenerative Amplifiers: Temporal Overlap of Femtosecond and Picosecond Light Pulses

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