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Quantification of Carbon Nanotubes by Raman Analysis
John A Lynch1,2, Quinn T Birch1, Thomas H Ridgway2
1Division of Applied Research and Technology, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati, OH, USA.
Annals of Work Exposures and Health
|May 3, 2018
Summary
Accurate monitoring of carbon nanotubes (CNTs) is crucial due to their increasing use. Raman spectroscopy shows promise for quantifying CNTs in suspensions and on filters, with improved detection limits for occupational exposure assessment.
Area of Science:
- Analytical Chemistry
- Materials Science
- Occupational Health
Background:
- Carbon nanotubes (CNTs) are increasingly used in various industries, raising concerns about potential health risks from exposure.
- Reliable and accurate methods for monitoring CNTs in the workplace are essential for ensuring safety.
Purpose of the Study:
- To evaluate two Raman spectroscopy-based methods for quantifying carbon nanotubes.
- To assess the feasibility of these methods for occupational exposure monitoring.
Main Methods:
- Quantification of CNTs in aqueous suspensions using Raman peak intensity.
- Raman mapping of CNTs collected on air filter surfaces as aerosols or small-area deposits.
Main Results:
- A strong correlation (R2 = 0.97) was observed between CNT concentration and Raman scattering intensity in suspensions, but measurement variance limited calibration.
- Raman mapping of filters showed correlation with CNT mass at higher surface densities (R2 = 0.83-0.95).
- Mapping larger areas improved precision and detection limits for lower-density samples, with an LOD of approximately 50 ng for small-area deposits.
Conclusions:
- Raman spectroscopy is a viable technique for CNT quantification, particularly for occupational monitoring of low-level deposits.
- Optimizing mapping strategies, such as increasing the mapped area, is key to overcoming challenges with heterogeneous samples and achieving lower detection limits.
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