The reactivity of surfactant films at natural air-water interfaces influences the properties of aerosol and the sea surface microlayer and their subsequent effects on the environment. Recent attention in the literature has focused on the possible role that interfaces can play in enhancing reactivity compared to the bulk, including the potential for changes in the direct photochemistry of organic species. The photochemistry of organic species is strongly-condition dependent, including changes due to pH, salinity, and ionization state, effects of which may be magnified at the surface.<br/>Here, we will discuss changes observed in response to environmental conditions at the air-water interface on the photochemistry, product formation, and surface properties of model photoactive surfactant films. Specifically, we will examine the reactivity of carboxylic acid and α-keto acid monolayer films using a Langmuir trough equipped with UV LEDs through both in situ surface tension measurements and offline product identification via ESI mass spectrometry. Comparison will be made to the bulk photochemistry of similar molecules, including the observed photochemically-driven self-assembly of three-dimensional aggregates. By examining the photoreactivity of these model surfactant films under varying subphase conditions, we aim to better understand the effects of sunlight-initiated reactions on the chemical and physical properties of aqueous aerosol.

Photochemistry at the air-water interface: Probing condition-dependent reactivity and phase behavior of model photoactive surfactant films

ACS Spring 2022

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