Elemental Composition of Freshly Nucleated ParticlesEPA Grant Number: R829622
Title: Elemental Composition of Freshly Nucleated Particles
Investigators: Johnston, Murray V.
Institution: University of Delaware
EPA Project Officer: Carleton, James N
Project Period: January 1, 2002 through December 31, 2004 (Extended to March 31, 2006)
Project Amount: $390,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Nanotechnology
The main objective of this work is to develop a method for real-time sampling and analysis of individual airborne nanoparticles in the 5 - 20 nm diameter range. The size range covered by this method is much smaller than existing single particle methods for chemical analysis. Since particles in this size range are close to their origin, chemical composition measurements should provide greater insight into particle formation mechanisms.
Nanoparticles will be classified by elemental composition using aerosol mass spectrometry. The aerosol will be drawn directly into a mass spectrometer where individual particles are analyzed in real time by laser ablation. To increase the sampling efficiency for particles in the 5 -20 nm diameter range, a quadrupole ion guide will be used to focus particles into the ablation laser beam path. Quantitative measurements of elemental composition will be achieved by complete atomization and ionization of individual particles using a high energy laser pulse to create a nano-plasma. This method will be used to study a variety of particle formation processes. While laboratory investigations are emphasized in this work, the instrumentation will be suitable for field experiments.
Nanometer diameter aerosol particles are important precursors of larger particles in the accumulation mode. There is growing evidence that ultrafine particles are toxic and that particle number can be an important indicator of human health. Controlling ultrafine particle concentrations requires an understanding of the gas phase condensation processes that lead to new particle formation. Measuring the elemental composition of individual, nanoparticles will help quantify the relative contributions of the various sources.