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

Kristian Laß, Joscha Kleber, and Gernot Friedrichs

Limnol. Oceanogr. Methods 8:216-228 (2010) | DOI: 10.4319/lom.2010.8.216

ABSTRACT: 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.