Current activities of ISO TC229/WG2 on purity evaluation and quality assurance standards for carbon nanotubes.

The current standardization activities of ISO (International Organization for Standardization) TC229 on "Nanotechnology" are introduced with focus on the work of WG2 (Working Group 2) for "measurement and characterization". Seven project groups of WG2 are actively preparing standard protocols (technical specifications) for characterization of single-wall carbon nanotubes (SWCNTs) by measurement methods such as TEM (transmission electron microscopy), SEM (scanning electron microscopy), EDX (energy-dispersive X-ray analysis), UV-Vis-NIR (ultraviolet-visible-near infrared) absorption spectroscopy, NIR-photoluminescence spectroscopy, EGA (evolved gas analysis)-GC-MS (gas chromatography-mass spectrometry), TGA (thermogravimetric analysis), and Raman spectroscopy; this work is described. The features of purity evaluation of SWCNTs by these methods are also briefly described and compared. Also described are two project groups of WG2 that are preparing standard protocols for characterization of multiwall CNTs (MWCNTs), aiming at the purity control by measurement of moisture content, ash content, metallic constituents, volatile content, polyaromatic hydrocarbon content, and carbon materials excluding MWCNTs. Other important properties for characterization of MWCNT, for example disorder, burning property, stacking nature, length, morphology, and inner/outer diameter, etc., are also mentioned. Finally, the importance and urgency of standardization for potential risk assessment of CNTs is briefly described, and current joint activity of ISO TC229 WG2 and WG3 for physicochemical characterization of engineered nanoscale materials for toxicological assessment is introduced.