Determination of photochemical properties of photosensitizers in tropospheric aqueous solution

Tamara Felber, Thomas Schaefer, and Hartmut Herrmann

Leibniz Institute for Tropospheric Research (TROPOS), Atmospheric Chemistry Department (ACD)

Permoserstraße 15, 04318 Leizpig, Germany

The presence of photosensitizers in the atmospheric particulate phase is an important new field of research of increasing activity and establish a new pathway of secondary organic aerosol (SOA) formation.1-7 However, kinetic and photochemical data as well as mechanisms of particle-phase reactions involving photosensitizers are still scarce.

In this study, the quantum yields of the excited triplet states of organic photosensitizers like imidazole-2-carboxaldehyde, benzophenone, and 4-benzoylbenzoic acid were determined by laser flash photolysis-laser long path absorption (LFP-LLPA). Spectroscopic studies were carried out using the LFP-LLPA setup to investigate time-resolved absorbance spectra (λ = 200 – 800 nm) of the excited triplet state of the photosensitizers as well as to observe their formation at a specific time after the laser pulse (tdelay = 100 ns – 300 µs).

The received data will be included into further studies to evaluate the importance of particle-/aqueous-phase chemistry of photosensitizers for atmospheric processes as well as the impact of photosensitized reactions on atmospheric particles possibly contributing to SOA formation.


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