This grant funds research by surface chemist Franz Geiger, Dow Professor of Chemistry at Northwestern University, that will investigate the fundamental chemistry of indoor surfaces. Using advanced spectroscopy, Geiger plans to expand our understanding of how indoor volatile and semivolatile organic compounds absorb from air to surfaces; how submonolayer amounts of these absorbed organic compounds convert into indoor molecular, nano-, and microlayers; the propensity of these newly formed layers to interact with oxidants; and how the dynamic response of molecular, nano-, and microlayers to gas-phase species vary with changes in relative humidity. The approach includes both mechanistic studies of idealized model surfaces as well as work on surfaces of samples derived from real-world indoor environments. Results will be shared through peer-reviewed publications and presentations at conferences and meetings.