AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Linking Vapor Uptake Coefficients to Shifts in Mobility for Cluster Ions and Nanoparticles
Vivek Rawat, Hui Ouyang, Derek Oberreit, Jikku Thomas, Carlos Larriba-Andaluz, CHRISTOPHER HOGAN JR., University of Minnesota
Abstract Number: 78 Working Group: Aerosol Physics
Abstract Tandem mobility analysis has been used for several decades to examine the extent of heterogeneous vapor uptake by nanoparticles. Traditionally, results have been quantified in terms of a dimensionless growth factor, i.e. the ratio of the particle mobility diameter at a particular saturation ratio to the mobility diameter under dry (zero saturation) conditions. However, for sub 2.0 nm clusters, the transient binding of a single vapor molecule can shift mobilities by an amount which is detectable with recently developed tandem ion mobility spectrometry-mass spectrometry systems. To better quantify such measurements, rigorous models linking mobility shifts to the binding of individual vapor molecules are required. In this presentation, we discuss the development of such models, in which we account for the change in mobility brought about by both the direct binding of vapor molecules as well as the change in gas composition associated with increasing saturation ratio. We show that it is possible to directly compare experimental measurements to predictions based upon classical nucleation theory as well as adsorption isotherms, and further that direct calculation of mobilities from all-atom models can be incorporated into calculations. Model predictions are compared to ion mobility spectrometry-mass spectrometry measurements of water vapor uptake by iodide salt ions and dimethylammonium bisulfate ions, as well as isopropanol uptake by polypeptide ions.