AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Real-Time Separation and Detailed Characterization of Aspherical Nanoparticles
ALLA ZELENYUK, David Bell, Jacqueline Wilson, Dan Imre, Pacific Northwest National Laboratory
Abstract Number: 385 Working Group: Instrumentation and Methods
Abstract Particle shape can play a central role in determining particle properties and behavior. Recently we developed a novel system that makes it possible to identify in real-time the presence of particles of different shapes, separate them based on their shape, and characterize their chemical and physical properties. In this system, a new-generation compact aerosol particle mass analyzer (APM) is used to classify particles with a narrow distribution of masses that are then further classified with a differential mobility analyzer (DMA) to generate an aerosol population with a single charge and narrow distributions of mobility diameters and shapes. Once classified, the compositions, morphologies and vacuum aerodynamic size distributions of these particles are characterized with our single particle mass spectrometer, SPLAT II.
We successfully applied the combined APM/DMA/SPLAT, or ADS, to characterize compact aspherical particles, like ammonium sulfate and NaCl, and fractal soot particles to determine particle mass, mobility and vacuum aerodynamic diameters, composition, morphology, density or effective density, and the dynamic shape factors (DSFs) in the transition and in the free-molecular regimes. In addition, for fractal particles, this approach provides information on particle fractal dimension, number and average diameter of primary spherules that comprise the fractal agglomerate, void fraction and surface area, all as a function of agglomerate size.
We will present the results of a study in which ADS was applied to gold nanospheres, nanorods, and nanowires with different sizes and aspect ratios. We show that it is possible to separate gold nanoparticles with different shapes, characterize their DSFs in the transition and in the free-molecular regimes, and determine intrinsic physical properties (mass, length, and aspect ratios). We also examine the alignment of nanorods and nanowires in the DMA and its effect on the measured mobility diameter that was previously used for separation of particles with high aspect ratios.