Study of Heterogeneous Nucleation upon Nanoparticles in Condensation Particle Counters (CPCs): Effects of Particle and Vapor Composition

摘要

Recent developments have led to significant reduction in the minimum size that can be detected with condensation particle counters (CPCs). While CPCs are widely used as particle detectors due to their high sensitivity and high signal-to-noise ratio, previous laboratory work shows that the activation efficiencies for particles smaller than 3nm are influenced by their chemical compositions and the condensing vapor, which lead to measurement uncertainties that are difficult to quantify. On the other hand, in spite of the work on heterogeneous nucleation in the past decades, discrepancies between measurements and theory still exist. In this study, we carry out experiments to explore the effects of nanoparticle chemical composition and electrical polarity (+1, 0, -1) on heterogeneous nucleation of several supersaturated vapors. Particle materials studied include (NaCl, W, Ag, and tetra-heptyl ammonium bromide and tetra-dodecyl ammonium bromide ions). Several condensing vapors (water, n-butanol, and diethylene glycol) were investigated. This study not only enriches our knowledge of activation efficiencies of different CPCs, which are essential for aerosol scientists who work with them, but also serves as an attempt to explore the fundamental scientific questions about heterogeneous nucleation.