Overview
ISO/TR 23173:2021 - Surface chemical analysis - Electron spectroscopies - Measurement of the thickness and composition of nanoparticle coatings - describes validated approaches to determine the thickness and chemical composition of coatings on core–shell and related nanoparticle morphologies using electron spectroscopy. The technical report focuses on X‑ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and synchrotron‑based electron spectroscopies, identifying assumptions, measurement challenges and sources of uncertainty. It also outlines protocols for nanoparticle sample analysis and lists complementary analytical techniques useful for interpreting electron spectroscopy data.
Key Topics
- Scope and definitions: Terms and symbols consistent with ISO surface‑analysis vocabulary (ISO 18115 series).
- XPS methods: Descriptive formulae for overlayer thickness, numerical modelling, variable excitation energy XPS, inelastic background analysis, near‑ambient‑pressure XPS (NAP‑XPS) and workflows for elemental composition extraction.
- AES methods: Non‑destructive and destructive depth‑profiling, imaging and line‑scan considerations for coated nanoparticles.
- Modelling & software: Use of numerical simulation and specialist packages (example: SESSA) to model XPS intensities and estimate coating thicknesses; Annex A provides an example MATLAB script for XPS modelling.
- Uncertainty & assumptions: Discussion of morphological deviations from ideal concentric core–shell particles, multilayer coatings and the impact of sample format, handling and provenance on surface measurements.
- Complementary analyses: Guidance on supporting techniques (e.g., TEM, SEM, SAXS/SANS, EDX, ICP‑AES, AFM) to improve confidence in thickness and composition interpretation.
Applications
ISO/TR 23173:2021 is directly applicable to laboratories and industries where accurate nanoparticle surface characterisation is critical:
- Nanomaterials research - catalyst design, core–shell syntheses and surface functionalisation studies.
- Biomedical and pharmaceutical development - nanoparticle coatings for drug delivery and biocompatibility.
- Energy and optoelectronics - functional coatings that define device performance.
- Regulatory testing and quality control - verifying coating thickness and surface composition for safety and compliance.
The guidance helps users select appropriate electron spectroscopy approaches and combine them with complementary methods to reduce ambiguity in coating thickness and composition measurements.
Who should use this standard
- Surface chemical analysts and metrology labs
- Nanomaterials scientists and R&D teams
- Instrument manufacturers and software developers for XPS/AES modelling
- Regulatory bodies and quality assurance units concerned with nanoparticle characterization
Related Standards
- ISO 18115‑1 / ISO 18115‑2 (surface chemical analysis vocabulary)
- ISO 20579 (sample handling and provenance for nanoparticle surface analysis)
- ISO/TR 14187 (general challenges in surface analysis of nanostructured materials)
Keywords: ISO/TR 23173:2021, nanoparticle coatings, XPS, AES, surface chemical analysis, coating thickness measurement, core‑shell nanoparticles, electron spectroscopies.