In-situ FTIR investigation of heterogeneous Langmuir monolayers at the air/water interface

In this study, we tried to measure ion reactivity at heterogeneous mixed Langmuir monolayers at the air/water interface by using in-situ near-normal external reflection FTIR spectroscopy. To achieve better spectral signals with less water vapor noise, close-packed monolayers of respective composition were chosen as backgrounds. Upon the adsorption of cadmium ions, the corresponding asymmetric carboxylate band clearly appeared. As the relative amount of non-reactive stearyl alcohols mixed with reactive stearic acids exceeded 15%, the adsorptivity of cadmium ions decreased nearly by half. The results have implications to molecular design of catalysts and biomineralization.