Infrared reflection absorption spectroscopy (IRRAS), also called infrared external reflection spectroscopy, is used for studying ultrathin hybrid clay films prepared by the Langmuir-Blodgett (LB) method. Infrared spectra of the hybrid films have been obtained at the air-water and air-solid (gold) interface. The presence of a smectite monolayer is observed when cationic surfactants are spread over the surface of a dilute aqueous smectite clay suspension. The in-plane ν(Si-O) band of saponite is observed in IRRAS spectra of saponite clay monolayers at the air-water interface. In contrast, the out-of-plane ν(Si-O) band at 1063 cm-1 is the dominant band in the p-polarized IRRAS spectra of a saponite monolayer deposited on a gold surface. These data correspond to the first-reported infrared spectra of clay minerals showing the enhancement of the out-of-plane vibrational modes and the nearly complete suppression of the in-plane vibrational modes. The results provide direct spectroscopic evidence confirming the orientation of the smectite particles parallel to the substrate.
- Blodgett films
- Infrared spectroscopy