Sum Frequency Generation Spectroscopy

Abstract Sum frequency generation (SFG) vibrational spectroscopy is a nonlinear optical vibrational spectroscopy, which has been shown to have submonolayer surface sensitivity. It has been developed into a powerful technique to investigate molecular structures of surfaces and interfaces. This paper introduces the technique of SFG spectroscopy and discusses several important SFG applications. One of the most important advantages of SFG over many traditional surface‐sensitive techniques is that SFG does not require high vacuum to operate. Therefore, it can be applied to investigate liquid surfaces and interfaces, as well as interfacial biological molecules in biologically relevant environments. The SFG applications discussed in this article are (i) simple liquid surfaces and interfaces, (ii) polymer surfaces in water and polymer/silane interfaces, and (iii) interfacial structures of peptides and proteins.