Imaging on surfaces with vibrational sum frequency generation microscopy

• Importance of spatial resolution on surface to provide average and distributions of molecular species. • Chemical mapping to interrogate specific regions of activity. • SFG provides many contrast mechanisms, chemical, orientational, lifetime, distribution width, among others. Nonlinear spectroscopy has been a valuable technique for probing surfaces for many decades. Still, in the recent past, nonlinear spectroscopy has become a useful tool for imaging monolayers on surfaces. This technique of nonlinear microscopy, more specifically sum frequency generation microscopy, provides both spectral and spatial information with varying resolution, allowing for the surface activity to be monitored and imaged. The following paper highlights the history, theory, and range of experimental advantages sum frequency generation imaging provides, focusing on specific experiments that put those advantages on display.