In Situ Method for Determining Combination of Organic Compounds Interacting with Each Other on Silicon Oxide Surface

Abstract

An experimental process for determining a combination of organic compounds, interacting with each other on a silicon oxide surface, was developed using a quartz crystal microbalance. The surface concentration of the four organic compounds, such as L-menthone (Mth), decylacetate (DA), diethylphthalate (DEP) and octanol (OCT), on a silicon oxide surface was evaluated in multi-component systems. The increase and decrease in the surface concentrations were not reversible with the changing gas phase concentrations in the two-component system consisting of Mth and DEP. Additionally, the small droplet shape of Mth placed on the DEP-coated glass plate surface was significantly different from that of DEP on the Mth-coated surface. Based on these results, Mth and DEP molecules were considered to have a significant interaction with each other. In any environment for industrial production and academic research, various kinds and amounts of organic and inorganic molecules are transported and adsorbed on a material surface in a multicomponent system. The material surface condition prepared in such an environment very often governs the final product quality including various functions present on the surface. [1][2][3][4][5][6][7] In order to achieve a desirable surface condition, the adsorption behavior of various compounds should be clarified. Particularly, the combination of compounds interacting with each other should be found by means of a simple and easy method.For this purpose, the molecular behaviors in single-component and multi-component systems have been studied by taking into account the physisorption and desorption rates using the quartz crystal microbalance (QCM). 8 The information obtained by the QCM could be understood by using the Multi-Component Organic Species Adsorption-Induced Contamination (MOSAIC) model in our previous studies 9-16 using isopropanol (IPA), octanol (OCT) and diethylphthalate (DEP). In previous studies, 13-16 the molecular interaction was found to be not significant among the IPA, OCT and DEP. These studies were based on the difference in the area occupied by the organic molecule in a multi-component system from that in a singlecomponent system. In order to show the capability for finding the existence of a molecular interaction, other organic molecules having various molecular structures should be evaluated. Additionally, the process for the measurement and the analysis should be simple and easy.For this purpose, organic compounds having characteristic shapes, such as L-menthone (Mth) and decylacetate (DA), are expected. DA has an asymmetric structure consisting of a long carbon chain and oxygen. Mth also has an asymmetric shape with cyclohexane and oxygen. The oxygens in both Mth and DA are expected to have a steric hindrance when being adsorbed on the silicon oxide surface, different from IPA, OCT and DEP. Additionally, for easily finding the existence of an interaction between various compounds, a simple process should be developed; the obtained conclusions are expected to be consistent...

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

“…Because the QCM frequency value was taken after the sufficiently long supply of the DEP and Mth, such as that longer than 120 s, the behavior at 25 °C showed that the surface concentration behavior was irreversible and similar to a previous study. 9 The surface concentrations at Conditions B, C and D at 25 °C in Fig. 11c were larger than those in Fig.…”

“…This behavior was the same as that in the previous study. 9 Next, the surface concentration was measured after the DEP vapor was supplied without the Mth vapor. Figures 11a and 11b show that the DEP concentration was 2.7 ng cm −3 while the Mth concentration was zero ng cm −3 under Condition A and at the temperature of 25 °C.…”