Adsorption and Desorption Dynamics of Sodium Dodecyl Sulfate at the Octadecylsilane Layer on the Pore Surface of a Mesoporous Silica Film Observed in-situ by Optical Waveguide Spectroscopy

The purpose of this study is to apply optical waveguide (OWG) spectroscopy to observe adsorption and desorption dynamics occurring in a surfactant-templated mesoporous silica film. For that purpose, a mesoporous silica (MS) film with open accessible pores (pore diameter, ca. 6 nm) was formed on an aluminum (Al) layer deposited on a glass substrate, and the pore surface of the MS film was modified with octadecylsilane (ODS). The resulting ODS-modified MS (ODS-MS) and Al multilayer film showed a clear waveguide coupling dip in the reflection spectrum. The position of the waveguide coupling dip was red-shifted as the amount of sodium dodecyl sulfate within the ODS-MS layer increases. These results indicate the usefulness of OWG spectroscopy for the study of adsorption/desorption dynamics occurring in MS materials.