Near Real-Time Measurement of Airborne Carbon Nanotubes with Metals Using Raman-Spark Emission Spectroscopy.

We present a near real-time measurement method that combines Raman and spark emission spectroscopy to quantitatively analyze the molecular structure of airborne single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), as well as detect toxic metals within CNTs. A corona-based aerosol microconcentrator was used for airborne CNTs sampling to enhance the measurement accuracy and sensitivity. The intensity of the characteristic Raman bands of CNTs and atomic emission lines of metals exhibited a linear relationship with the analyte mass, yielding high coefficient R² values. By carefully selecting appropriate signal peaks for calibration, we achieved a limit of detection (LOD) in terms of air concentration as low as 0.09 μg/m³ for SWCNT and 0.81 μg/m³ for MWCNT with a sampling time of 10 min. Additionally, our method exhibited excellent performance in measuring metals, with a mass LOD of 0.8-0.9 ng for Co and Ni and a mass LOD of 35.09 ng for Fe. The method performed well for the measurement of CNT and relevant metal composition with advantages of near real-time monitoring, low LOD, and portable use, making it a valuable tool for various applications in nanomaterial analysis.