Issue 2, 2016

Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging


Organic aerosol particles (OA) play major roles in atmospheric chemistry, climate, and public health. Aerosol particle viscosity is highly important since it can determine the ability of chemical species such as oxidants, organics or water to diffuse into the particle bulk. Recent measurements indicate that OA may be present in highly viscous states, however, diffusion rates of small molecules such as water are not limited by these high viscosities. Direct observational evidence of kinetic barriers caused by high viscosity and low diffusivity in aerosol particles were not available until recently; and techniques that are able to dynamically quantify and track viscosity changes during atmospherically relevant processes are still unavailable for atmospheric aerosols. Here we report quantitative, real-time, online observations of microscopic viscosity changes in aerosol particles of atmospherically relevant composition, using fluorescence lifetime imaging (FLIM) of viscosity. We show that microviscosity in ozonated oleic acid droplets and secondary organic aerosol (SOA) particles formed by ozonolysis of myrcene increases substantially with decreasing humidity and atmospheric oxidative aging processes. Furthermore, we found unexpected heterogeneities of microviscosity inside individual aerosol particles. The results of this study enhance our understanding of organic aerosol processes on microscopic scales and may have important implications for the modeling of atmospheric aerosol growth, composition and interactions with trace gases and clouds.

Graphical abstract: Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging

Supplementary files

Article information

Article type
Edge Article
10 Aug 2015
07 Nov 2015
First published
12 Nov 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 1357-1367

Author version available

Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging

N. A. Hosny, C. Fitzgerald, A. Vyšniauskas, A. Athanasiadis, T. Berkemeier, N. Uygur, U. Pöschl, M. Shiraiwa, M. Kalberer, F. D. Pope and M. K. Kuimova, Chem. Sci., 2016, 7, 1357 DOI: 10.1039/C5SC02959G

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