Light-absorbing products of atmospheric oxidation of indole

Title: Light-absorbing products of atmospheric oxidation of indole by hydroxyl radical, nitrate radical and ozone

This talk will present results from the paper by Baboomian et al. (2023) “Light absorption and scattering properties of indole secondary organic aerosol prepared under various oxidant and relative humidity conditions” published in AS&T, as well as new unpublished results on the mechanism of indole oxidation by nitrate radial. The key points of the presentation are: (a) the major product of oxidation of indole by nitrate radical is identified as 3-nitroindole, unambiguously confirmed with reference standards; (b) quantum mechanical calculations suggest that the reaction proceeds by an unusual mechanism, starting from an abstraction of a hydrogen atom from nitrogen rather than carbon in indole; (c) the absorption coefficients for the indole?+?NO3 aerosol particles have a strong and non-monotonic dependence on relative humidity, suggesting two competing reaction mechanisms for the chromophores, and highlighting the complex effect of water on the absorption coefficient of SOA from heterocyclic aromatic precursors.

About the speaker: Sergey Nizkorodov was born in 1971 in Almaty, Kazakhstan. He received his undergraduate degree in biochemistry from Novosibirsk State University, Russia, in 1993 and graduate degree in physical chemistry from Basel University, Switzerland, in 1997. After doing his postdoctoral research in chemical kinetics and reaction dynamics at the University of Colorado at Boulder, and in atmospheric chemistry at the California Institute of Technology, he joined the faculty of the Department of Chemistry, University of California, Irvine (UCI) in 2002. He teaches general, analytical, and atmospheric chemistry courses at UCI, and does research on chemistry of particulate matter in the ambient atmosphere and in indoor environments using state-of-the-art spectroscopic and mass-spectrometric techniques. He has been a research mentor to over 100 graduate, undergraduate, high-school, and postdoctoral students. His research, education, service and public outreach work have been recognized by several awards including Fulbright Scholarship, AAAS Fellowship, Camille Dreyfus Teacher-Scholar Award, AGU Ascent Award, Coblentz Award, UCI Chancellor's Award for Excellence in Fostering Undergraduate Research, Daniel G. Aldrich, Jr. Distinguished University Service Award, and UCI Professor of the Year Award. He served as the President of the American Association for Aerosol Research (AAAR) in 2020-21, a professional organization of about 1000 scientists and engineers working to advance the field of aerosol research and technology, and been active in various service roles at UCI and in the research community.