Abstract
Recent studies on infrared and Raman spectra of monolayers, bilayers, and Langmuir-Blodgett (LB) films are reviewed. Regarding infrared measurements of these films, the transmission, attenuated total reflection (ATR), reflection-absorption (R-A), and surface electromagnetic wave (SEW) techniques are outlined. For Raman measurements, on the other hand, the external reflection, optical waveguide, and total internal reflection techniques are briefly described. The advancement of these techniques and the improvement in sensitivity of infrared and Raman spectrophotometers allowed us to study the structure and molecular orientation even in single monolayers at various interfaces.
The infrared ATR spectroscopy of stearic acid LB films indicates that there exists the structural and orientational heterogenity among the first few monolayers. The R-A spectroscopy of cadmium arachidate LB films suggests the almost perpendicular orientation of the molecular axis on the silver substrate as well as significant disruption of molecular conformation and lateral packing during heating and melting processes. Application, of the total internal reflection spectroscopy to the study on resonance Raman spectra of spread monolayers on water and of adsorbed monolayers at an oil-water interface indicates changes in molecular orientation and interaction with changes in the amount of molecules in the monolayers.
