AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Surface Enhanced Raman Spectroscopy (SERS): Enhanced Detection of Organic Species in Individual Aerosol Particles
REBECCA CRAIG, Amy Bondy, Joel Rindelaub, Paul Shepson, Andrew Ault, University of Michigan
Abstract Number: 127 Working Group: Instrumentation and Methods
Abstract Surface enhanced Raman spectroscopy (SERS) provides direct, spectroscopic observation of the chemical complexity of individual atmospheric aerosol particles at ambient pressure and temperature. SERS improves the detection of low concentration analytes by using metal nanoparticles to enhance the Raman signal of functional groups present. SERS analysis of ambient particles from a forested region impacted on silver nanoparticle coated quartz substrates allowed for observation of an array of spectral features previously undetectable through Raman microspectroscopy. Of particular interest were organic functional groups due to secondary organic aerosol (SOA) material formed by oxidation of biogenic volatile organic compounds (BVOCs) at the single particle level. With hundreds to thousands of different chemical species present in individual particles, species present at femtogram to attogram levels were detected using SERS. While SOA composition is often assumed to be homogenous between and within individual particles, SERS analysis revealed substantial particle-to-particle variability, as changes on scales less than 1 micron were observed. Experimentally collected spectra, along with density functional theory (DFT) calculations, of standards of low-volatility organic species predicted to be in the particle phase have been used to gain insight into the functional groups from different species present in these aerosol particles. SERS has great potential to improve analysis of aerosol particles, specifically composition, mixing state, and internal structure, which affect a particle’s optical properties and water uptake.