Measuring particle size-dependent physicochemical structure in airborne
single walled carbon nanotube agglomerates |
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Authors: | Andrew D Maynard Bon Ki Ku Mark Emery Mark Stolzenburg Peter H McMurry |
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Institution: | (1) Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies, One Woodrow Wilson Plaza, 1300 Pennsylvania Avenue NW, Washington, DC 20004, USA;(2) Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, OH 45226, USA;(3) Mechanical Engineering Department, University of Minnesota, 111 Church Street, Minneapolis, MN 55455, USA |
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Abstract: | As-produced single-walled carbon nanotube (SWCNT) material is a complex matrix of carbon nanotubes, bundles of nanotubes (nanoropes),
non-tubular carbon and metal catalyst nanoparticles. The pulmonary toxicity of material released during manufacture and handling
will depend on the partitioning and arrangement of these components within airborne particles. To probe the physicochemical
structure of airborne SWCNT aggregates, a new technique was developed and applied to aerosolized as-produced material. Differential
Mobility Analysis-classified aggregates were analyzed using an Aerosol Particle Mass Monitor, and a structural parameter Γ
(proportional to the square of particle mobility diameter, divided by APM voltage) derived. Using information on the constituent
components of the SWCNT, modal values of Γ were estimated for specific particle compositions and structures, and compared
against measured values. Measured modal values of Γ for 150 nm mobility diameter aggregates suggested they were primarily
composed of non-tubular carbon from one batch of material, and thin nanoropes from a second batch of material – these findings
were confirmed using Transmission Electron Microscopy. Measured modal values of Γ for 31 nm mobility diameter aggregates indicated
that they were comprised predominantly of thin carbon nanoropes with associated nanometer-diameter metal catalyst particles;
there was no indication that either catalyst particles or non-tubular carbon particles were being preferentially released
into the air. These results indicate that the physicochemistry of aerosol particles released while handling as-produced SWCNT
may vary significantly by particle size and production batch, and that evaluations of potential health hazards need to account
for this.
Disclaimer: The mention of any company or product does not constitute an endorsement by the Centers for Disease Control and
Prevention. The findings and conclusions in this paper are those of the authors and do not necessarily represent the views
of the National Institute for Occupational Safety and Health. |
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Keywords: | aerosol carbon nanotubes differential mobility analysis aerosol particle mass monitor composite nanoparticles occupational health |
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