AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Oxidation of C60 Aerosol by Ozone
ANDREA TIWARI, Alec Wagner, John Morris, Linsey Marr, Virginia Tech
Abstract Number: 437 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Manufactured carbonaceous nanoparticles, such as C$_(60) fullerenes, will enter the atmosphere during production, use, and disposal. There, they will be subject to physical and chemical transformations which could modify their properties and ultimately their fate, transport, and toxicity within the environment. The objective of this research is to determine the products and rates of reaction of aerosolized C$_(60) with atmospherically relevant concentrations of ozone. Batch reactions were carried out in a 6-m$^3 Teflon chamber at ozone mixing ratios of 45 – 120 ppb. C$_(60) aerosols were introduced into the chamber through dispersion of powdered C$_(60).The resulting concentration was 9.3 +/- 2.6 x 10$^4 particles cm$^(-3), and the size distribution peaked around 100 nm. Following exposure to ozone, aerosols were collected onto filters, gold slides, and copper grids for analysis by high performance liquid chromatography (HPLC), reflection absorption infrared spectroscopy (RAIRS), and transmission electron microscopy (TEM). Results indicate that the reaction proceeded within minutes and appeared to be complete in less than 1 h. It did not depend on initial ozone mixing ratio. After 1 h, the C$_(60) aerosols took up 11 +/- 3 ppb of ozone, and C$_(60) concentrations decreased by 10-20%. Reaction products included the primary ozonide (C$_(60)O$_3), a C$_(60) epoxide (C$_(60)O), as well as higher oxides and may also have included an oxygen-linked C$_(60) polymer. The majority of the aerosols remained soluble in toluene, but this fraction decreased with exposure time. The reaction products were not appreciably soluble in water. These results suggest that at atmospherically relevant ozone levels, C$_(60) is rapidly oxidized and that this process may affect its fate and transport in the environment. Other carbonaceous nanomaterials such as carbon nanotubes may be subject to similar transformations.