Identifying Photocharring of Single Particles in an Aerosol Raman Hyperspectral Imaging Instrument

MAXWELL FREEMAN, J. Alex Huffman, University of Denver

     Abstract Number: 677
     Working Group: Instrumentation and Methods

Abstract
Raman spectroscopy is a powerful tool for identification of aerosol particle composition, however the excitation source may induce photochemical transformations that alter the compositions–and therefore the Raman spectra–of particles under interrogation. Here we test a specific photochemical transformation, photocharring, with a previously described aerosol Raman hyperspectral imager (ARHI) that is commercially available through Battelle as the Resource Effective Bio-Identification System (REBS). The REBS is equipped with a 50 mW 638 nm LED laser which was used to interrogate mineral dusts, crystallized organic acids, particles composed of common biopolymers, and primary biological aerosol particles (PBAP). Replicate spectra from single particles and composite spectra from the replicates were evaluated to identify instances when photocharring occurred. Darker particles that absorbed more visible wavelengths of light were more likely to be photocharred than less absorptive, lighter particles.