Synchronized Structure and Surface Tension Measurement on Individual Secondary Aerosol Particles by Low-Voltage Transmission Electron Microscopy

A number of physical and chemical models have been built to describe secondary aerosols (SAs) in the atmosphere; however, direct experimental approaches to simultaneously characterizing the chemical structures and physical properties on the single-particle level are lacking. This lack obscures our understanding of SA formation mechanisms and impedes the development on the accurate prediction and control of air pollution. Here we obtained clear core−shell structural information about the aqueous aerosols employing low-voltage transmission electron microscopy−energy dispersive spectroscopy. The prevalent 10−20% surface tension reduction due to organic matter partitioning has been unveiled. Further analysis and modeling show that smaller SAs can yield greater surface tension reduction, while the pronounced surface tension reduction may enlarge the size of SAs by ≤50%. Our work paves the way for an unprecedented comprehensive single-particle study of the global atmospheric SA problem.