AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Tandem DMA Measurement of the Evaporation of Sub 5nm Metal Nanoparticles
CARLOS LARRIBA, Santiado Ruiz-Valdepeñas, Christopher Hogan Jr., University of Minnesota
Abstract Number: 68 Working Group: Aerosol Physics
Abstract The evaporation rate of small particles (< 5 nm) is theoretically expected to increase due to the Kelvin effect. If the particles are charged, conversely, with further decreasing size, the evaporation rate is expected to slow, as the predicted vapor pressure of charged clusters decreases to negligibly small values as the cluster size decreases (the Thomson effect). The Kelvin and Thomson effects are also the bases for classical nucleation theory (the Kelvin effect) as well as ion-induced nucleation theory (the Kelvin and Thomson effect combined), and are therefore of considerable importance. However, the actual validity of these theoretically derived effects for small particles remains in question. We use tandem differential mobility analysis (DMAs) to examine the evaporation of sub-5 nm diameter silver particles, produced with a hot wire generator. In these experiments, the evaporation of mobility classified silver particles is facilitated by a temperature controlled microfurnace. The DMAs employed, 1/2 mini DMAs, are of modest to high resolving power (~12-25) and are capable of mobility classifying singly charged particles up to 10 nm diameter down to the sizes of individual molecular ions. To our knowledge, this is the first time that such experiments have been performed for such small sized particles, with a combined experimental and theoretical effort to quantitatively monitor dissociation (evaporation) kinetics of ionized metal clusters.