Water Soluble Gases and Their Interactions with TiO₂ Surfaces

The concentration of water soluble organic gases within indoor environments is 15 times higher than outdoors (Duncan et al., 2018). The sources of these gases include daily activities (like cooking and use of cleaning and consumer products), oxidation of gas-phase volatile organic compounds and human metabolism through the skin. Since a substantial amount of residential homes experience dampness due to water vapor condensation on surfaces from human activities, presence of mold, or high relative humidity (Duncan et al., 2018), these organic gases can uptake liquid water on indoor surfaces and assimilate into the aqueous phase. However, there is a lack of understanding of the surface reaction mechanisms of these organic gases in the indoor environments. Thus, to better understand the indoor air composition and to identify any potential health hazards, it is important to study the interactions between water soluble organic compounds and how they partition to the indoor surfaces. Furthermore, the presence of carbon dioxide and ammonia in the indoor environments can influence the pH indoors. The surface chemistry of these water soluble organic gases can be affected by the change in pH, which will also be explored in our studies.

Specifically, in the Grassian lab, we focus on elucidating the surface chemistry of various water-soluble organic gases on titanium dioxide nanoparticle surfaces, which is a component of paints and self-cleaning surfaces, in contact with a thin water layer of several microns in thickness as a model for water condensed onto indoor surfaces. For these experiments, we employ spectroscopic (ATR-FTIR) and quantitative (QCM) techniques. The compounds of interest include lactic acid, pyruvic acid, glyoxal, and methyl glyoxal, which are indoor gases that have been measured in emissions from building occupants and fireplaces.

References

Duncan, S. M.; Sexton, K. G.; Turpin, B. J. Oxygenated VOCs, Aqueous Chemistry, and Potential Impacts on Residential Indoor Air Composition. Indoor Air 2018, 28, 198–212.