ISO/TR 23173:2021

TECHNICAL ISO/TR
REPORT 23173
First edition
2021-06
Surface chemical analysis — Electron
spectroscopies — Measurement of
the thickness and composition of
nanoparticle coatings
Analyse chimique des surfaces — Spectroscopies d'électrons —
Mesurage de l'épaisseur et de la composition des revêtements de
nanoparticules
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 1
5 Overview . 3
6 X-ray photoelectron spectroscopy. 4
6.1 General . 4
6.2 Coating thickness measurement. 4
6.3 Nanoparticle coating thickness . 5
6.4 Numerical methods . 6
6.5 Descriptive formulae. 9
6.6 Modelling and simulation software .11
6.7 Method comparisons .12
6.8 Inelastic background analysis .15
6.9 Elemental composition .16
6.10 Variable excitation energy XPS .18
6.10.1 General.18
6.10.2 Qualitative depth-profiling . .19
6.10.3 Quantitative depth-profiling .22
6.11 Near-ambient-pressure XPS (NAP-XPS) .23
6.11.1 General.23
6.11.2 Internal structure of bimetallic NP catalysts .24
6.11.3 Measurement of NP's in liquid suspension .24
7 Auger electron spectroscopy .26
7.1 General .26
7.2 Coating thickness measurement.26
7.2.1 General.26
7.2.2 Destructive depth-profiling .27
7.2.3 Non-destructive depth-profiling .27
7.2.4 Elemental composition . .27
7.2.5 Imaging and line scans.28
8 Complementary analysis .30
9 Deviations from ideality .33
9.1 General .33
9.2 Multilayered coatings .33
9.3 Other non-ideal cases .35
Annex A (informative) Example script for modelling of XPS data from nanoparticles .40
Bibliography .42
Foreword
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This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 7, Electron spectroscopies.
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iv © ISO 2021 – All rights reserved

Introduction
Recently, there has been increasing development and use of nanoparticles in a wide range of application
[1]–[7]
areas, including catalysis, medicine, energy, optoelectronics and cosmetics . In particular,
nanoparticles having some form of coating layer, which is present either by design or due to incidental
[8]–
processes such as contamination or oxidation, are among the most commonly studied and utilised
[11]
. An essential part of the characterisation of nanoparticles is the measurement of the surface
properties because a large proportion of the material is at a surface or interface. In the case of coated
nanoparticles, the thickness and composition of the coating has a significant role determining its
functional properties and defines the interaction of the particle with its environment. Many applications
require nanoparticles to have coatings that are specifically designed in order to achieve a desired
level of performance. Measurement of surface composition and coating thickness of nanoparticles
is a challenge to which electron spectroscopies are well suited, due to high surface sensitivity, well-
understood physical principles and accessibility. Such measurements can have a significant dependence
on sample format and condition; sample handling and provenance of nanoparticle samples for surface
[12]
chemical analysis are addressed in ISO 20579 . A general introduction to the challenges of surface
[13]
chemical analysis of nanostructured materials is provided in ISO/TR 14187 .
TECHNICAL REPORT ISO/TR 23173:2021(E)
Surface chemical analysis — Electron spectroscopies
— Measurement of the thickness and composition of
nanoparticle coatings
1 Scope
This document provides a description of methods by which the coating thickness and chemical
composition of "core-shell" nanoparticles (including some variant and non-ideal morphologies) can
be determined using electron spectroscopy techniques. It identifies the assumptions, challenges,
and uncertainties associated with each method. It also describes protocols and issues for the general
analysis of nanoparticle samples using electron spectroscopies, specifically in relation to their
importance for measurements of coating thicknesses.
This document focuses on the use of electron spectroscopy techniques, specifically X-ray photoelectron
spectroscopy, Auger electron spectroscopy, and synchrotron-based methods. These cannot provide all
of the information necessary for accurate analysis and therefore some additional analytical methods
are outlined in the context of their ability to aid in the interpretation of electron spectroscopy data.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 18115-1, Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in
spectroscopy
ISO 18115-2, Surface chemical analysis — Vocabulary — Part 2: Terms used in scanning-probe microscopy
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115-1 and ISO 18115-2
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols and abbreviated terms
X subscripts den
...