The utility of Raman spectra in aiding the interpretation of surface structure at aqueous interfaces

In this perspective, we review how Raman spectroscopy of bulk aqueous phases can assist in the interpretation of surface-selective vibrational spectra obtained from visible-infrared sum-frequency generation experiments. This overcomes the limitations associated with a reliance on spectral fitting to study characteristic vibrational modes of all species and thereby provides an all-experimental route for analysis of spectral features, including cases where spectra are available in only a single set of beam polarizations. The basic principle is based on two-dimensional correlation analysis, a generalized method with broad applicability, but most well-known in its application to vibrational spectra. We provide an example of the type of information that can be obtained when using heterospectral correlation that includes both sum-frequency and Raman data. The combination of these methods can help to unravel characteristic features of aqueous interfaces such as the surface preference of adsorbed species relative to their bulk concentration.

Automated summary

This perspective discusses the use of Raman spectroscopy to interpret surface-selective vibrational spectra in bulk aqueous phases. By overcoming the limitations of spectral fitting, it provides an experimental route for analyzing spectral features, even in cases with only a single set of beam polarizations. Two-dimensional correlation analysis is used as a general method, with a specific application to vibrational spectra. The combination of sum-frequency and Raman data allows for unraveling characteristic features of aqueous interfaces, such as the surface preference of adsorbed species relative to their bulk concentration.