AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Surface Enhanced Raman Spectroscopy Enabled Observations of Previously Undetectable Secondary Organic Aerosol Functional Groups and Intra-Particle Variation at the Individual Particle Level
ANDREW AULT, Rebecca Craig, Amy Bondy, University of Michigan
Abstract Number: 196 Working Group: Aerosol Chemistry
Abstract Surface enhanced Raman spectroscopy (SERS) analysis of ambient particles from a forested region provides the first direct, spectroscopic observation of the complexity of organic species resulting from secondary organic aerosol (SOA) formed by oxidation of biogenic volatile organic compounds (BVOCs) at the single particle level. An array of spectral features resulting from organic functional groups due to SOA material were observed in individual atmospheric particles impacted on silver nanoparticle-coated substrates. SERS improves the detection of critical trace components, permits < 1µm spatial information to be obtained, and facilitates the probing of particle phase and internal structure. Enhanced Raman scattering was detected, particularly in the fingerprint region, allowing for the detection of moieties present in femtogram to attogram quantities. These measurements represent the first application of SERS to study ambient atmospheric particles. Additionally, compositional differences on ~ 500 nm spatial scales were observed with Raman microspectroscopy for the first time. These differences are believed to be related to viscosity-limited diffusion of species within particles leading to complex internal structure. While SOA composition is frequently assumed to be homogeneous between and within individual particles, substantial particle-to-particle variability in SOA composition was observed, which must be understood for accurate modeling of SOA production and climate effects.