What Is the Driving Force behind the Adsorption of Hydrophobic Molecules on Hydrophilic Surfaces?

Abstract

The adsorption of limonene, a common organic compound found in indoor air, on hydrophilic surfaces such as glass (SiO 2 ), a prevalent surface in the indoor environment, is poorly understood. In this study, we have investigated the interaction of limonene and three other cyclic hydrocarbons (cyclohexane, cyclohexene, and benzene) on hydroxylated SiO 2 using infrared spectroscopy and ab initio molecular dynamics (AIMD) simulations. Experimental results show that there is an interaction between these cyclic hydrocarbons and surface hydroxyl groups. AIMD simulations demonstrate that all of the cyclic molecules, except for cyclohexane, π-hydrogen bond with surface hydroxyl groups while cyclohexane interacts with the surface OH groups through dispersion forces. According to experiments and simulations, the intermolecular interaction between limonene and SiO 2 is significantly stronger than those of other compounds explored. This study provides an understanding of some of the driving forces behind the formation of organic coatings on glass surfaces important in indoor environments.

A molecular picture of surface interactions of organic compounds on prevalent indoor surfaces: limonene adsorption on SiO2

“…The height and location of the first peak in the RDFs for the C* up and C* down configurations are the same, indicating that the strength of π–H bonding in the two configurations is similar. These values are in close agreement with the RDFs calculated using ab initio MD simulations 37…”

The atmospheric chemistry of indoor environments

“…With the enormous heterogeneity of indoor spaces, indoor chemistry models have to be tested against measurements in a wide range of environments, to assess the degree to which their predictions are quantitatively accurate and transferable. A modeling consortium has been formed with a hierarchical approach to the development of indoor modeling, 4 an approach that is already providing insights into fundamental interactions of gases with building materials 152,260 and the heterogeneous chemistry that occurs when ozone interacts with within skin oils and clothing. 204,205 This approach is required because detailed processes at the molecular level can not be directly incorporated into models that capture air motions using computational uid dynamics.…”

Indoor Surface Chemistry: Developing a Molecular Picture of Reactions on Indoor Interfaces

“…2 Thus, the overall human exposure to gases and particulate matter (PM) is often greater in indoor environments than that found outdoors, yet, there remains a great deal about the chemistry of indoor environments that is not well understood from a detailed molecular perspective. This lack of scientific understanding is related to many unique sources, 3 complex heterogeneous and multiphase chemical reactions, 4,5 the high surface-to-volume ratio, 6,7 and factors not present in outdoor environments (e.g., building materials, furnishings, ventilation, indoor lights, etc.) that all play a key role in indoor air chemistry and indoor air quality (Figure 1).…”