PNNL

Abstract

A significant fraction of atmospheric particles are composed of inorganic substances that are mixed or coated with organics. The behavior of these particles depends on the particle internal composition and on the arrangement of the specific constituents in each particle. It is important to know which constituent is on the surface and whether it entirely covers the particle surface. We present a study that demonstrates that an instrumental system that includes an ultra-sensitive single particle mass spectrometer that is coupled with a differential mobility analyzer can be used to quantitatively measure in real-time individual particle composition, size, density, shape and determine which substance is on the surface and whether it entirely covers the particle. Here we use liquid dioctyl phthalate to coat NaCl seeds and generate spherical particles that are encapsulated with the organic coat and pyrene, a solid poly aromatic hydrocarbon, to produce aspherical particles with pyrene nodules and exposed NaCl cores. We show that the behavior of the mass spectral intensities as a function of laser fluence yields information that can be used to determine the morphological distribution of individual particles constituents.