CEN ISO/TS 23359:2025

SLOVENSKI STANDARD
01-november-2025
Nanotehnologije - Kemijska karakterizacija dvodimenzionalnih materialov,
podobnih grafenu, v prahu in tekoči disperziji (ISO/TS 23359:2025)
Nanotechnologies - Chemical characterization of graphene-related two-dimensional
materials from powders and liquid dispersions (ISO/TS 23359:2025)
Nanotechnologien - Chemische Charakterisierung von Graphen in Pulvern und
Suspensionen (ISO/TS 23359:2025)
Nanotechnologies - Caractérisation chimique des matériaux bidimensionnels similaires
au graphène dans les poudres et les suspensions liquides (ISO/TS 23359:2025)
Ta slovenski standard je istoveten z: CEN ISO/TS 23359:2025
ICS:
07.120 Nanotehnologije Nanotechnologies
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN ISO/TS 23359
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
September 2025
TECHNISCHE SPEZIFIKATION
ICS 07.120
English Version
Nanotechnologies - Chemical characterization of
graphene-related two-dimensional materials from
powders and liquid dispersions (ISO/TS 23359:2025)
Nanotechnologies - Caractérisation chimique des Nanotechnologien - Chemische Charakterisierung von
matériaux bidimensionnels similaires au graphène à Graphen in Pulvern und Suspensionen (ISO/TS
partir de poudres et de dispersions liquides (ISO/TS 23359:2025)
23359:2025)
This Technical Specification (CEN/TS) was approved by CEN on 23 August 2025 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 23359:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (CEN ISO/TS 23359:2025) has been prepared by Technical Committee ISO/TC 229
"Nanotechnologies" in collaboration with Technical Committee CEN/TC 352 “Nanotechnologies” the
secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO/TS 23359:2025 has been approved by CEN as CEN ISO/TS 23359:2025 without any
modification.
Technical
Specification
ISO/TS 23359
First edition
Nanotechnologies — Chemical
2025-08
characterization of graphene-
related two-dimensional materials
from powders and liquid
dispersions
Nanotechnologies — Caractérisation chimique des matériaux
bidimensionnels similaires au graphène à partir de poudres et de
dispersions liquides
Reference number
ISO/TS 23359:2025(en) © ISO 2025

ISO/TS 23359:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO/TS 23359:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 4
5 Approaches to chemical characterization . 5
6 X-ray photoelectron spectroscopy (XPS) . 8
6.1 Introduction .8
6.2 Instrument preparation .8
6.3 Sample preparation .8
6.4 Method .9
6.5 Quantitative analysis . 12
7 Thermogravimetric analysis (TGA) .13
7.1 Introduction . 13
7.2 Sample preparation . 15
7.2.1 General . 15
7.2.2 Instrument conditions and preparation . . 15
7.2.3 Preparation of crucible . 15
7.2.4 Measurement procedure . 15
7.3 Data processing and quantitative analysis .16
7.3.1 Data plotting .16
7.3.2 Determination of the number of mass change steps .16
7.3.3 Determination of the temperature of maximum mass change rate (T ) .17
max
7.3.4 Identification of the GR2M present .17
7.3.5 Determine mass percentage .17
8 Inductively coupled plasma mass spectrometry (ICP-MS) . 19
9 Fourier-transform infrared spectroscopy (FTIR). 19
10 Reporting . 19
10.1 Introduction .19
10.2 X-ray photoelectron spectroscopy (XPS) . 20
10.3 Thermogravimetric analysis (TGA). 20
10.4 Inductively coupled plasma mass spectrometry (ICP-MS) . 20
10.5 Fourier-transform infrared spectroscopy (FTIR) . 20
Annex A (informative) Inductively coupled plasma mass spectrometry (ICP-MS) .21
Annex B (informative) Fourier-transform infrared spectroscopy (FTIR) .26
Annex C (informative) Summary of X-ray photoelectron spectroscopy (XPS) interlaboratory
studies .29
Annex D (informative) Summary of thermogravimetric analysis (TGA) interlaboratory study .34
Annex E (informative) Summary of inductively coupled plasma mass spectrometry (ICP-MS)
interlaboratory study . 41
Annex F (informative) Summary of Fourier-transform infrared spectroscopy (FTIR) mini-
interlaboratory study .44
Bibliography . 47

iii
ISO/TS 23359:2025(en)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not
received notice of (a) patent(s) which may be required to implement this document. However, implementers
are cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held
responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
In the IEC, see www.iec.ch/understanding-standards.
This document was prepared jointly by Technical Committee ISO/TC 229, Nanotechnologies, and Technical
Committee IEC/TC 113, Nanotechnology for electrotechnical products and systems, in collaboration with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 352, Nanotechnologies, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/TS 23359:2025(en)
Introduction
Graphene nanoplatelets (GNPs) are applied in many technology areas, including solar cells, biosensors,
displays, composites, flexible electronics and energy storage, due to the exceptional properties of graphene.
However, it is not just GNPs that are used commercially but other material variants as well, such as reduced
graphene oxide, graphene oxide and chemically functionalised forms of GNPs. These different graphene-
related two-dimensional materials (GR2Ms) are suitable for different application areas and therefore, there
must be a full understanding of the chemical properties of commercially available materials, so that the
correct material is selected for specific application areas.
As these materials are increasingly used in different industries, international standardization is needed
to support commercialization. Reliable, accurate, and reproducible measurements are important due to
the multiple production routes and therefore variability in properties. Producers of the material must use
standards to maintain quality in manufacture and confidence in the supply chain.
This document specifies methods to measure the chemical properties of powders and dispersions
containing a GR2M. The techniques covered are X-ray photoelectron spectroscopy (XPS), thermogravimetric
analysis (TGA), inductively coupled plasma mass spectrometry (ICP-MS), and Fourier-transform infrared
spectroscopy (FTIR). These techniques determine the elemental composition, oxygen to carbon ratio, trace
metal impurities, weight percentage of chemical species and the functional groups present.
XPS is used to provide quantitative measurements of the surface elemental composition of GR2Ms. It can
measure every element except hydrogen and helium that are within up to approximately 10 nm of the
surface and at equivalent homogeneous concentrations above the XPS detection limit.
TGA is a common material characterization technique available in research and industry labs, which offers
rapid and simple characterization of bulk material properties providing useful qualitative and quantitative
information. TGA is widely used for characterization of GR2M to determine the amount of impurities (i.e.
water, amorphous carbon, metals), presence of functional groups, traces of surfactants or other organic
impurities from fabrication processes or impurities from the initial raw material (graphite, silica, metal
oxides etc).
ICP-MS is used to provide detection of the trace metal impurities in samples containing graphene related
two-dimensional materials. However, using conventional solution sample introduction ICP-MS, the sample
must be completely solubilized and hence digestion of the samples is required using harsh acid and
microwave treatment before analysis using ICP-MS.
FTIR is used to understand the functional groups that are present for different materials with significant
non-carbon elements, already identified using complementary techniques herein.

v
Technical Specification ISO/TS 23359:2025(en)
Nanotechnologies — Chemical characterization of graphene-
related two-dimensional materials from powders and liquid
dispersions
1 Scope
This document specifies methods for characterizing the chemical properties of powders or liquid dispersions
containing graphene-related two-dimensional material (GR2M), using a set of suitable measurement
techniques.
This document covers the determination of elemental composition, oxygen to carbon ratio, trace metal
impurities, weight percentage of chemical species and functional groups present, by use of the following
techniques:
— X-ray photoelectron spectroscopy (XPS);
— thermogravimetric analysis (TGA);
— inductively coupled plasma mass spectrometry (ICP-MS);
—Fourier-transform infrared spectroscopy (FTIR).
This document covers sample preparation, protocols and data analysis for the different techniques.
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 15472, Surface chemical analysis — X-ray photoelectron spectrometers — Calibration of energy scales
ISO 16129, Surface chemical analysis — X-ray photoelectron spectroscopy — Procedures for assessing the day-
to-day performance of an X-ray photoelectron spectrometer
ISO 18115-1, Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in spectroscopy
ISO 20903, Surface chemical analysis — Auger electron spectroscopy and X-ray photoelectron spectroscopy —
Methods used to determine peak intensities and information required when reporting results
ISO 21270, Surface chemical analysis — X-ray photoelectron and Auger electron spectrometers — Linearity of
intensity scale
ISO 24237, Surface chemical analysis — X-ray photoelectron spectroscopy — Repeatability and constancy of
intensity scale
ISO 80004-1, Nanotechnologies — Vocabulary — Part 1: Core terms
ISO/TS 80004-6, Nanotechnologies — Vocabulary — Part 6: Nano-object characterization
ISO/TS 80004-13, Nanotechnologies — Vocabulary — Part 13: Graphene and other two-dimensional (2D)
materials
ISO/TS 23359:2025(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115-1, ISO 80004-1,
ISO/TS 80004-6, ISO/TS 80004-13 and the following apply.
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology 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/
3.1
graphene
graphene layer
single-layer graphene
monolayer graphene
single layer of carbon atoms with each atom bound to three neighbours in a honeycomb structure
Note 1 to entry: It is an important building block of many carbon nano-objects.
Note 2 to entry: As graphene is a single layer, it is also sometimes called monolayer graphene or single-layer graphene
and abbreviated as 1LG to distinguish it from bilayer graphene (2LG) and few-layered graphene (FLG).
Note 3 to entry: Graphene has edges and can have defects and grain boundaries where the bonding is disrupted.
Note 4 to entry: In situations where the word graphene is used as an adjective, including in terms such as graphene-
enabled, the term commonly and incorrectly refers to GR2M (3.7) and not just to single-layer graphene.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.1.]
3.2
graphite
allotropic form of the element carbon, consisting of graphene layers stacked parallel to each other in a three-
dimensional, crystalline, long-range order
Note 1 to entry: Adapted from the definition in the IUPAC Compendium of Chemical Terminology.
Note 2 to entry: There are two primary allotropic forms with different stacking arrangements: hexagonal and
rhombohedral.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.2]
3.3
bilayer graphene
2LG
two-dimensional material consisting of two well-defined stacked graphene layers
Note 1 to entry: If the stacking registry is known, it can be specified separately, for example, as “Bernal stacked bilayer
graphene”.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.7]
3.4
few-layer graphene
FLG
two-dimensional material consisting of three to ten well-defined stacked graphene layers
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.11]

ISO/TS 23359:2025(en)
3.5
graphene nanoplatelet
GNP
nanoplate consisting of graphene layers
Note 1 to entry: GNPs typically have thickness of between 1 nm to 3 nm and lateral dimensions ranging from
approximately 100 nm to 100 μm.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.12]
3.6
graphene oxide
GO
chemically modified graphene with extensive oxidative modification of the basal plane
Note 1 to entry: Graphene oxide is a single-layer material with a high oxygen content, typically characterized by O/C
atomic ratios of approximately 0,5 (C/O ratios of approximately 2,0)  depending on the method of synthesis.
Note 2 to entry: Graphene oxide is predominately prepared by oxidation and exfoliation of graphite.
Note 3 to entry: Oxidative modification can also occur at the edges.
Note 4 to entry: Restacking of graphene oxide can occur. Therefore, care must be taken when preparing samples or
products from highly concentrated liquid dispersions as this can lead to agglomeration and aggregation of the primary
particles, which are a single-layer.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.15]
3.7
graphene related 2D material
GR2M
carbon-based two-dimensional material consisting of one to 10 layers, including graphene, graphene oxide,
reduced graphene oxide, and functionalized variations thereof
Note 1 to entry: This includes bilayer graphene, trilayer graphene and few-layer graphene.
Note 2 to entry: The terms graphene-based material and graphene-material are deprecated here. They have been used
to describe materials other than graphene, such as graphene oxide.
Note 3 to entry: "Graphene-related 2D material" is defined in contrast with graphene-based and GR2M-based .
[SOURCE: ISO/TS 80004-13:2024, 3.1.1.2]
3.8
reduced graphene oxide
rGO
reduced oxygen content form of graphene oxide
Note 1 to entry: This can be produced by chemical, thermal, microwave, photo-chemical, photo-thermal or microbial
or bacterial methods, or by exfoliating reduced graphite oxide.
Note 2 to entry: If graphene oxide was fully reduced, then graphene would be the product. However, in practice, some
3 2
oxygen containing functional groups will remain and not all sp bonds will return back to sp configuration. Different
reducing agents will lead to different carbon to oxygen ratios and different chemical compositions in reduced
graphene oxide.
Note 3 to entry: It can take the form of several morphological variations such as platelets and worm-like structures.
Note 4 to entry: The O/C atomic ratio is approximately 0,1 to 0,5 (C/O ratio 2 to 10).
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.16]

ISO/TS 23359:2025(en)
3.9
graphite oxide
chemically modified graphite prepared by extensive oxidative modification of the basal planes
Note 1 to entry: The structure and properties of graphite oxide depend on the degree of oxidation and the particular
synthesis method.
Note 2 to entry: In powder form, restacking of graphite oxide layers can occur.
[SOURCE: ISO/TS 80004-13:2024, 3.1.2.14]
3.10
X-ray photoelectron spectroscopy
XPS
method in which an electron spectrometer is used to measure the energy distribution of photoelectrons and
Auger electrons emitted from a surface irradiated by X-ray photons
Note 1 to entry: X-ray sources in common use are unmonochromated Al Kα and Mg Kα X-rays at 1 486,6 eV and
1 253,6 eV, respectively. Modern instruments also use monochromated Al Kα X-rays. Some instruments make use of
various X-ray sources with other anodes or of synchrotron radiation.
Note 2 to entry: Extended pressure XPS (EP-XPS), near ambient pressure XPS (NAP-XPS) and hard X-ray photo electron
spectroscopy (HAXPES) are variants of XPS.
[SOURCE: ISO 18115-1:2023, 11.6, modified — Abbreviations in Note 2 to entry have been spelt out]
3.11
thermogravimetric analysis
TGA
method in which the change in the mass of a sample is measured as a function of temperature while the
sample is subjected to a controlled temperature programme
[SOURCE: ISO/TS 80004-6:2021, 6.1.2, modified — Term has been changed to “thermogravimetric analysis”.]
3.12
inductively coupled plasma mass spectrometry
ICP-MS
analytical technique comprising a sample introduction system, an inductively coupled plasma source
for ionization of the analytes, a plasma or vacuum interface and a mass spectrometer comprising an ion
focusing, separation and detection system
[SOURCE: ISO/TS 80004-6:2021, 5.23]
3.13
Fourier transform infrared spectroscopy
FTIR
spectroscopy in which a sample is subjected to excitation of molecular bonds by pulsed, broad-band infra-
red radiation, and the Fourier transform mathematical method is used to obtain an absorption spectrum
[SOURCE: ISO/TS 80004-6:2021, 5.8]
4 Abbreviated terms
For the purposes of this document, the following symbols and abbreviations apply.

ISO/TS 23359:2025(en)
1D one dimensional
1LG single layer graphene
2D two-dimensional
2LG bilayer graphene
3D three dimensional
DTG first derivative of the TG curve
d2TG second derivative of the TG curve
FLG few-layer graphene
FTIR Fourier-transform infrared spectroscopy
GNP graphene nanoplatelet
GR2M graphene related two-dimensional material
HAXPES hard X-ray photo electron spectroscopy
ICP-MS inductively coupled plasma mass spectrometry
SCA surface chemical analysis
TG thermogravimetric
TGA thermogravimetric analysis
XPS X-ray photoelectron spectroscopy
5 Approaches to chemical characterization
There are a number of different techniques that can be used to measure the chemical properties of GR2Ms.
Each technique provides different measurands and information. The techniques outlined in this document
are XPS, TGA, ICP-MS, and FTIR. Table 1 provides a summary of the methods and approaches to chemical
characterization.
ISO/TS 23359:2025(en)
Table 1 — Approaches to chemical characterization

Technique Measurands Analysis size Limitations

Quantitative elemental
Limits of detection between
Surface measurement with analysis
analysis (atomic per-
XPS (see 0,01 % and 0,5 % for every element
depth down to 10 nm.
cent).
Clause 6) present in the surface analysis
Lateral resolution: ≈ 1 to ≈1 000 μm.
region (except H and He).
Oxygen-to-carbon ratio.
Moisture content.
Mass percentage of
Requires complementary meth-
TGA (see combustible chemical
Bulk measurement ods for identification of chemical
Clause 7) species identified.
species.
Non-combustible impu-
rities.
ICP-MS (see
Microwave and acidic digestion of
Clause 8 and Trace metal impurities. Bulk measurement
material required before analysis.
Annex A)
Sensitivity requires significant
FTIR (see levels (several atomic percent)
Chemical functional
Clause 9 and Bulk measurement of chemical functionalization.
groups.
Annex B) Requires samples to be thoroughly
dehydrated.
NOTE: XPS can also provide:
a) chemical state information (not covered in this document);
b) X to carbon ratios where X is any element measured other than carbon.
Oxygen to carbon ratios are particularly useful for information when analysing rGO and GO.
Follow the sequence of measurement methods and process outlined in Figure 1 to determine the chemical
properties of GR2Ms. Firstly, undertake XPS to determine quantitative elemental analysis, the main
measurand for chemical measurement, and, if required, chemical state information. Then, decide if any
additional measurands are required. If so, undertake a combination of TGA, ICP-MS, or FTIR, as appropriate.
The sample may be a powder or a liquid dispersion (suspension). For liquid dispersions, samples are dried
to a powder form, in some cases on a substrate, to undergo further characterization. Liquid dispersions can
include other formulated ingredients which, when dried, will lead to the inclusion of these chemicals in the
sample to be analysed.
ISO/TS 23359:2025(en)
NOTE The numbers relate to the clauses where the method is detailed.
Figure 1 — Sequence of methods used to determine chemical properties of GR2Ms from powder or
liquid dispersion
The storage and laboratory humidity levels should be monitored as, depending on the sample, these can play
a role in varying the chemical functionalization of GR2M.
As well as chemical properties, the structural properties of the GR2M should be considered and can be
important for cross comparison with the chemical measurements. Refer to ISO/TS 21356-1 for information
on structural characterization of graphene from powders and liquid dispersions, using techniques such as
Raman spectroscopy, the Brunauer-Emmett-Teller (BET) method, atomic force microscopy, scanning electron
microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED).
NOTE ISO/TR 19733 outlines other techniques that can provide chemical analysis. This includes X-ray diffraction
and combustion techniques. These techniques currently have unknown uncertainties but can provide useful
information for quality control purposes once a material has been measured using the methods outlined in this
document.
ISO/TS 23359:2025(en)
6 X-ray photoelectron spectroscopy (XPS)
6.1 Introduction
XPS can be used to investigate the surface chemistry of GR2M samples. It provides chemical information
from the top ≤10 nm of a sample with a spatial resolution typically between approximately ten to a few
hundred micrometres. The following information should be measured:
— elemental composition with typically 0,1 atomic percent sensitivity;
— chemical binding state information (if required).
In addition, XPS is able to provide information on:
a) thickness measurement of overlayers of less than 10 nm on a substrate;
b) surface chemical imaging with a resolution of typically approximately 10 μm;
c) depth-distribution of chemical species through angle-resolved analysis, background shape analysis and
sputter depth profiling.
XPS works by irradiating a sample with X-rays (commonly Al Kα or Mg Kα) in vacuum. When an X-ray
photon hits and transfers this energy to a core-level electron, the photoelectron is emitted from its initial
state with a kinetic energy dependent on the incident X-ray and binding energy of the atomic orbital from
which it originated. The energy and intensity of the emitted photoelectrons are analysed to identify and
determine the concentrations of the elements present. The chemical state of the atom influences the binding
energy scale position and the shape of photoelectron peak in the spectrum and these can be used to infer the
chemical environment of the atom by expert analysis.
6.2 Instrument preparation
The user should be competent in XPS analysis and should, as far as possible, conform to ISO 10810. Prior to
measurements, the XPS instrument shall be in good working order. The linear range of operation shall be
determined using ISO 21270. The energy scale of the instrument shall be calibrated using ISO 15472. The
intensity scale of the operating modes used for quantitative elemental analysis shall be calibrated according
to laboratory practice. It should be calibrated by the instrument manufacturer or appropriate metrology
institute. It is normal for these steps to be carried out after the installation or at a regular instrument service,
in which case the stability of the instrument shall be assessed using ISO 16129 and ISO 24237. Details of the
instrument calibration and sensitivity factors employed should be recorded in accordance with ISO 15470.
6.3 Sample preparation
The test sample consisting of a GR2M should be measured after directly pressing a powder into a pellet,
which produces a flat homogenous surface for XPS and addresses any possible health and safety concerns
due to the possible nano-particulate nature of the material. An example of a pressed pellet mounted on a
1 cm × 1 cm silicon wafer is shown in Figure 2. The use of a pressed pellet will produce the most repeatable
results. As an alternative to pressing pellets, the powders may be mounted and analysed as received but the
results are likely to be less repeatable. The powders may also be mounted in a recessed well, but the powder
must be well fixed in the recess to avoid any damage to or contamination of the XPS equipment. Whichever
sample preparation is used, the sample preparation procedure should be recorded. In most cases, the sample
preparation procedure will affect the measured result. Results measured on pellets should not be compared
with results from powders.
ISO/TS 23359:2025(en)
Figure 2 — Example of a pressed pellet mounted on a silicon wafer
The contamination of samples must be avoided during sample preparation. Disposable laboratory gloves
and masks should be used. The surfaces of pellet dies should be free from contaminants. Sample preparation
should be performed in a well-ventilated area. A relative humidity of higher than 60 % should be avoided.
Samples should only be handled with clean metal implements. The area to be analysed should not be touched.
For further information on sample preparation, refer to ISO 20579-1:2024, Clause 5 and Annex B.
The sample preparation should be documented as described in ISO 20579-4, Clause 5 and Annex B.
Once the test samples are prepared, position the sample in the instrument in accordance with standard
operating procedures.
Other types of samples should not be put onto the sample holder with the test samples, in order to avoid
contamination.
6.4 Method
The method shall be as follows:
a) Achieve a suitable vacuum, according to standard operating procedures. The instrumental vacuum
-6 -8
should be better than approximately 10 Pa (10 mbar) during data acquisition.
b) A survey scan with a minimum pass energy of 80 eV or higher shall be acquired. The kinetic energy
range shall be from 200 eV to at least 10 eV greater than the X-ray energy. The energy step size shall
be 1 eV or smaller. The dwell time or number of sweeps shall be adjusted to ensure that the number of
counts of C 1s maximum is greater than 1 × 10 counts per second (or counts/s).
c) Acquire high resolution (narrow) scans with a pass energy of 40 eV or lower for appropriate peaks. The
energy step size should be between 0,05 eV and 0,1 eV. High resolution scans of C 1s, O 1s, N 1s, Cl 2p, and
S2p regions are recommended as a minimum, if the elements are identified as present as well as regions
for other elements expected or suspected to be present and elements identified in the survey scan.
For example, if fluorine is expected to be present either as the GR2M has been functionalized with
fluorine or fluorine is expected to be a contaminant, then a high-resolution scan of F 1s is recommended.
In order to obtain good signal quality, the test samples should be scanned until a peak intensity of greater
than 2 × 10 counts/s is recorded at the C 1s maximum. Peaks of all other elements should be scanned
for the same number of scans as the C 1s peak, or a greater number of scans should be performed. For
each high-resolution spectra, a total energy window of at least three times the width of the main peak
should be used. In addition, for the C 1s, the scan energy window should extend at least 15 eV to the
higher binding energy side of the peak to account for peak asymmetry. An example of the survey scan
for a GR2M sample and a narrow scan of the C1s peak is shown in Figure 3.

ISO/TS 23359:2025(en)
NOTE An alternative procedure is to first run survey scans as described in b). Then run elemental detailed
narrow scans acquired at approximately 80 eV resolved pass energy and with the energy step size 0,1 eV, for all
elements detected in the survey spectra and use these for quantitative analysis. As the next step, acquire high-
resolution spectra with a pass energy 40 eV or lower and with the energy step size between 0,05 eV to 0,1 eV
according to c), but only for the elemental peaks where the chemical shifts are smaller and high-resolution scans
are therefore needed. For GR2M powders, this most likely only includes the elemental peaks C 1s, O 1s and N 1s, Cl
2p and S 2p.
d) A minimum of 3 measurements overall [following steps b) and c)] should be obtained at different
positions on each powder sample. A second or third sample, i.e. duplicate or triplicate samples, can
be analysed to check repeatability, which can show any issues with sample preparation. If triplicate
samples are analysed, then one measurement per sample can be sufficient.
This assumes that the analysis area is several hundred microns by several hundred microns, such that the
analysis will be for the average value for many micrometre sized GR2M particles. If the analysis area is
smaller than this, then additional measurement positions are recommended.
The acquisition conditions should be recorded and reported. If samples experience charging during
measurement, then appropriate charge compensation systems shall be used, for example an electron flood
gun can be used. The details of operation should be recorded in accordance with ISO 19318.

ISO/TS 23359:2025(en)
a) Survey scan of a GR2M sample
b)Narrow scan of a C 1s peak of a GR2M sample

ISO/TS 23359:2025(en)
Key
X binding energy, eV
-1
Y intensity, counts s
1 C KLL peak
2 O KLL peak
3 F 1s peak region if present
4 O 1s
5 N 1s peak region if present
6 C 1S
Figure 3 — Example XPS spectrum
6.5 Quantitative analysis
The equivalent-homogeneous relative content of carbon, oxygen, sulphur, chlorine, and nitrogen and
any other detected elements shall be calculated from a selected peak area from each of the detected
elements in the survey scan (or alternatively quantification from the elemental detailed narrow spectra).
The homogeneous equivalent atomic concentration is the atomic concentration that can result in the
measured relative peak intensities if the sample were homogeneous. I.e. if the sample is homogeneous, the
homogeneous equivalent atomic concentration is the true atomic concentration. Only data acquired using
the same instrument settings, such as pass energy, shall be used. If any element detected in the survey scan
is excluded from the analysis, then this shall be noted. Undertake the following steps:
a) Select the integral range of the detected elements, with a wide enough integral energy interval to
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