Raman Microprobe Characterization of Residual Carbonaceous Material Associated with Urban Airborne Particulates

Abstract

Analyses of individual urban airborne particulates were conducted in the Raman microprobe. In addition to the spectral features characteristic of the particle, two features at ∼1350 and ∼1600 cm⁻¹ have been observed. The appearance of these bands is found to vary a function of the laser irradiance. By modeling experiments, it is demonstrated that these two bands can be explained by the presence of carbon in a form analogous to polycrystalline graphite. In air particulates the source of the carbon can be either “graphitic soot” or an organic “contaminant” which converts to polycrystalline graphite upon exposure to the laser beam.