Temperature Influence on Organic Molecular Interaction on Silicon Oxide Surface In Situ Measured Utilizing a Quartz Crystal Microbalance

The influence of temperature on the molecular interaction between diethylphthalate (DEP) and L-Menthone (Mth) on a silicon native oxide surface was in situ real time evaluated utilizing a quartz crystal microbalance. By increasing the temperature from 25 °C to 35 °C in a single component system, the physisorption and desorption rate constants of DEP increased, while those of Mth showed significantly small changes. Simultaneously, the surface concentrations of DEP and Mth decreased with the increasing temperatures. In the two-component system, the surface concentration was measured by alternatively changing gas phase concentrations of DEP and Mth in order to evaluate whether it irreversibly or reversibly changed. Because the surface concentration change was irreversible at 25 °C, the molecular interaction between the DEP and Mth was considered to exist. In contrast, the change became reversible with the increasing temperature to produce a negligible molecular interaction between them. Such a behavior change occurred in the temperature range less than 10 °C. The low surface concentration by the increasing temperature was considered to weaken the attractive molecular interaction.