Overview
ISO/TS 10868:2017 - Nanotechnologies - Characterization of single-wall carbon nanotubes using ultraviolet-visible–near infrared (UV‑Vis‑NIR) absorption spectroscopy - provides practical guidelines for using optical absorption spectroscopy to characterize compounds containing single‑wall carbon nanotubes (SWCNTs). The Technical Specification defines a measurement method to estimate mean SWCNT diameter (applicable from 1 nm to 2 nm), an optically defined purity indicator, and an optically derived ratio of metallic SWCNTs to total SWCNT content.
Key Topics
- Measurement principle: Uses UV‑Vis‑NIR absorption spectra and absorbance (−log(I/I0)) to identify interband optical transitions (van Hove singularity peaks) specific to SWCNTs.
- Spectral features: Identification of S11, S22 (semiconducting) and M11 (metallic) absorption peaks and a broad π‑plasmon background in the UV.
- Diameter estimation: Relates optical transition energies/wavelengths to mean SWCNT diameter based on tight‑binding/zone‑folding relationships; suitable for diameters between 1–2 nm.
- Purity indicator (optical): Derived from ratios of SWCNT-specific peak areas to total absorption (including π‑plasmon background); indicates relative carbonaceous content but not absolute mass purity.
- Metallic ratio: Determined from integrated peak areas of metallic and semiconducting regions (formulas provided for R), with caveats about extinction coefficients and diameter dependence.
- Sample preparation & instrumentation: Guidance on dispersions (aqueous and solvent), surfactants (e.g., DOC, SDS, SDBS), solid films and use of UV‑Vis‑NIR spectrometers; measurement conditions and data analysis procedures are specified.
- Limitations & uncertainty: Requires well‑resolved peaks and similar diameter distributions for valid comparisons; surfactants and dispersing agents can affect spectra. Measurement uncertainties and reporting requirements are addressed.
Applications and Users
ISO/TS 10868:2017 is aimed at:
- Materials scientists and researchers characterizing SWCNT batches by spectroscopy.
- Manufacturers and quality control labs performing routine SWCNT quality assessment (diameter distribution, optical purity, metallic content indicator).
- Metrology labs and testing facilities developing standardized nanomaterial characterization workflows.
- Regulatory and compliance teams needing documented, repeatable optical methods for SWCNT characterization.
Practical uses include batch-to-batch comparison, process monitoring, and screening prior to more invasive techniques (TEM, TGA) for complementary information.
Related Standards
- ISO/TS 80004‑4 (Nanotechnologies - Vocabulary - Part 4: Nanostructured materials) - referenced terminology.
- ISO documents on thermogravimetric analysis and metal impurity characterization (e.g., ISO TS 11308) are complementary for assessing metallic catalyst residues that optical methods cannot detect.
Keywords: ISO/TS 10868:2017, SWCNT, single‑wall carbon nanotubes, UV‑Vis‑NIR absorption spectroscopy, nanotube diameter, purity indicator, metallic SWCNT ratio, nanotechnologies, spectroscopy.