Toward a molecular understanding of the surface composition of organic particles

What is it about?

This research describes an analytical method that enables measurement of the surface layer composition of model airborne particles without interference from the bulk composition. We describe this unique ionization method that does not use an external source of energy such as light or electron impact, but is able to generate mass spectra primarily from the surface layer molecules of submicron organic particles, something that to date very few methods have been able to do.

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Photo by Aron Visuals on Unsplash

Photo by Aron Visuals on Unsplash

Why is it important?

Inhalable airborne particles have outsized effects on health, visibility, and climate. While the surface makes up a small fraction of the particle mass, incoming gases interact at this interface first. It is expected that a number of processes are controlled by the composition of the surface of particles, including heterogeneous reactions, particle growth, water uptake and interactions with biological systems. There are few methods that enable surface layer composition to be probed for airborne particles in their native state, i.e. "on the fly", without employing energetic processes that alter the composition. This research describes an analytical method that enables soft ionization measurement of the surface layer composition of such particles. The surface sensitivity of this unique ionization method provides a path forward for understanding the role of the surface in determining particle chemical and physical properties.