The evolution of total internal reflection Raman spectroscopy for the chemical characterization of thin films and interfaces.

Abstract

Total internal reflection (TIR) optical spectroscopies have been widely used for decades as non-destructive and surface-sensitive measurements of thin films and interfaces. Under TIR conditions, an evanescent wave propagates into the sample layer within a region approximately 50nm to 2μm from the interface, which limits the spatial extent of the optical signal. The most common TIR optical spectroscopies are fluorescence (i.e., TIRF) and infrared spectroscopy (i.e., attenuated total reflection infrared). Despite the first report of TIR Raman spectroscopy appearing in 1973, this method has not received the same attention to date. While TIR Raman methods can provide chemical specific information, it has been outshined in many respects by surface-enhanced Raman spectroscopy (SERS). TIR Raman spectroscopy, however, is garnering more interest for analyzing the chemical and physical properties of thin polymer films, self-assembled monolayers (SAMs), multilayered systems, and adsorption at an interface. Herein, we discuss the early experimental and computational work that laid the foundation for recent developments in the use of TIR Raman techniques. Recent applications of TIR Raman spectroscopy as well as modern TIR Raman instruments capable of measuring monolayer-sensitive vibrational modes on smooth metallic surfaces are also discussed. The use of TIR Raman spectroscopy has been on a rise and will continue to push the limits for chemical specific interfacial and thin film measurements. Graphical abstract Total internal reflection (TIR) Raman spectroscopy can extract the chemical and physical information from thin films and adsorbates.