AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Imaging Aqueous Submicron Particles through the Development of a Flash Freeze Technique
THERESA KUCINSKI, Miriam Freedman, The Pennsylvania State University
Abstract Number: 481 Working Group: Instrumentation and Methods
Abstract Understanding aerosol effects on Earth’s climate is dependent on particle characterization which requires the development of new analytical techniques. In particular, methods to study morphology and phase are needed to encompass a broad size regime that can range from nanometer to micrometer particles. It is also crucial to include the study of morphology in relation to relative humidity (RH) to be able to predict the phase state of aerosol particles in the atmosphere. Particles can undergo liquid-liquid phase separation (LLPS) with cycling humidity levels and the resulting phase state can alter the physics and chemistry of aerosol particles in the atmosphere. Furthermore, it has been shown that LLPS is size dependent in the submicron range when imaging dried particles. LLPS has been well documented at the micrometer scale through the use of optical microscopy that allows for imaging of particles over a range of RH values. However, studies of phase separation in aqueous submicron particles over a range of RH remain elusive due to limitations of current techniques. We developed a flash freeze technique to capture submicron particles through a range of RH values and image via cryogenic transmission electron microscopy (cryo-TEM). The method is similar to the vitrification technique found in biosciences but instead utilizes a temperature controlled flow tube that vitrifies particles equilibrated at a chosen RH. The flash freeze method allows for imaging of aqueous multicomponent aerosol particles at multiple points in the phase transition region. With this technique, we have characterized the phase transition region for the following multicomponent systems: 2-methylglutaric acid/ammonium sulfate, 1,2,6-hexanetriol/ammonium sulfate, and a complex organic mixture/ammonium sulfate. These characterizations provide new insight into the process of LLPS for submicron aerosol particles.