ISO 20579-4:2018

INTERNATIONAL ISO
STANDARD 20579-4
First edition
2018-04
Surface chemical analysis —
Guidelines to sample handling,
preparation and mounting —
Part 4:
Reporting information related to the
history, preparation, handling and
mounting of nano-objects prior to
surface analysis
Analyse chimique des surfaces — Lignes directrices pour la
manipulation, préparation et montage des échantillons —
Partie 4: Exigences de rapport sur les nanomatériaux, défis en matière
d'analyse et méthodes d'extraction des solutions
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Provenance information to be collected or retained regarding the history, handling,
storage and processing of nano-objects prior to submission for surface analysis .2
4.1 Information record . 2
4.2 As-synthesized and as-prepared materials . 3
4.3 After testing, exposure, treatment or retrieval . 4
5 Information to be reported related to preparing and mounting of nanomaterials for
surface chemical analysis . 4
5.1 General . 4
5.2 Initial form or packaging of sample . 4
5.3 Analysis objective or special requirements . 4
5.4 Description of method used to prepare samples for analysis . 4
5.5 Method of mounting sample for analysis (see ISO 20579-1 and ISO 20579-2
for examples) . 5
Annex A (informative) Needs for enhanced documentation and application of surface
chemical analysis methods to assist in identifying and avoiding artefacts and
misinterpretations involving research and applications of nano-objects .6
Annex B (informative) Example methods for extraction of nano-objects from solution for
surface analysis and issues for dispersion of dry particles .10
Annex C (informative) Example sample data: collected, recorded and reported for Ag
nanoparticles provided by BAM .16
Bibliography .20
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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 ISO documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 201, Surface Chemical Analysis,
Subcommittee SC 2, General Procedures.
A list of all parts in the ISO 20579 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

Introduction
Introduction to the ISO 20579 series
This series is intended to assist analysts and those seeking surface chemical analysis in the handling,
storage, mounting and treatment of specimens. This is a multipart document, with the first two
parts being general requirements for sample handling and storage in ISO 20579-1, and mounting
and treatment of samples in ISO 20579-2. The ensuing parts combine new requirements of sample
handling/storage and/or sample mounting/preparation for new materials classes. ISO 20579-3
focuses on biomaterials and ISO 20579-4 focuses on reporting needs for nano-objects. Each part of this
document can be used independently of the other parts, although the general procedures described
in Parts 1 and 2 are applicable to a wide range of materials and are not reproduced in the materials-
specific documents.
Although primarily prepared for the surface-analysis techniques of Auger-electron spectroscopy (AES),
X-ray photoelectron spectroscopy (XPS) and secondary-ion mass spectrometry (SIMS), the methods
described in this document are also applicable to many other surface-sensitive analytical techniques
such as ion-scattering spectrometry, scanning probe microscopy, low-energy electron diffraction
and electron energy-loss spectroscopy, where specimen handling can influence surface-sensitive
measurements. AES, XPS and SIMS are sensitive to surface layers that are typically a few nanometers
in thickness. Such thin layers might be subject to severe perturbations caused by specimen handling or
surface treatments that could be necessary prior to introduction into the analytical chamber. Proper
handling and preparation of specimens is particularly critical for dependable analysis. Improper
handling of specimens can result in alteration of the surface composition and unreliable data.
Introduction to this document
Although all types of samples requiring surface analysis need thoughtful preparation, as noted in
[1]
ISO 20579-1 and ISO 20579-2 , nano-objects present additional challenges in order to avoid artefacts
[2]
due to the handling and preparation of materials prior to analysis . The types of procedures described
in ISO 20579-1 and ISO 20579-2 apply generally to nanomaterials, but because of the nature of nano-
objects it is important to carefully document how these and other procedures are implemented. This
document indicates the minimum information regarding sample preparation that needs to be reported
about the handling and preparation for surface analysis that should become part of sample provenance
information to help assure the reliability and usefulness of data obtained from surface-analysis
[3]
methods . Informative Annex A provides a background to some unique aspects of nano-objects that
amplify the reporting needs. Informative Annex B provides an overview of practices used by research
groups around the world to extract particles from solution in preparation for surface chemical analysis,
and Annex C shows an example of a sample data form. Although focused on surface chemical analysis of
nano-objects, many issues apply to nanomaterials more generally.
Nanomaterials include both materials with their internal or surface structures in the nanoscale, i.e.
nanostructured materials, and objects with one or more external dimensions in the nanoscale, i.e. nano-
objects. Nano-objects, in particular, present a range of characterization challenges that have the potential
[4-10]
to inhibit or delay the scientific and technological impacts of nanoscience and nanotechnology .
The standardization of these characterization methods is led by ISO TC 229 (nanotechnologies) with
many standards on particle size measurement produced by ISO TC 24/SC 4. Because nano-objects are
comprised to a large degree of surfaces and interfaces, the importance of adequate characterization
[4][11]
of their surfaces and interfaces has been highlighted by many and the roles of surface chemical
[12]
analysis methods for nanomaterial characterization are discussed in ISO/TR 14187 .
Many nano-objects are produced and stored in conditions far from a state of equilibrium, making them
particularly susceptible to change as a function of time, upon exposure to different environments, during
[4]
handling and when subjected to different measurements . Seemingly minor variations in synthesis,
age or source of precursor chemicals, processing or storage have been found to produce materials
[13-15]
with significantly different properties or lifetimes . The large impact of such minor changes
complicates the ability of experiments to be reproduced and emphasizes the importance of sample
history in providing complete information about a sample and the impacts of analysis. These types
of issues have led the Organisation for Economic Co-operation and Development (OECD) to prepare a
guidance document dealing with sample preparation and dosimetry for safety testing of manufactured
nanomaterials. The guidance includes an indication of the many factors that can influence materials
relative to safety testing and indicates information that should be reported. However, these issues have
impacts well beyond safety testing.
Many nano-objects are produced or stored in liquid environments. Although it is well recognized
[4][9]
that it is important to analyse materials in their ‘natural’ environment when possible , methods
often used to characterize surfaces of nano-objects involve removing materials from the natural or
working environments and exposure to ambient and/or vacuum environments. A variety of approaches
are being used to transport materials from the natural environment and to present the material for
analysis, attempting to maintain or maximize the useful information that can be extracted from the
analysis. Both care during the sample preparation, storage and processing, and accurate reporting of
the process are critical to reliable understanding of the measurement results.
Accurate reporting of the sample handling and history of nano-objects is required to reproduce and
[3][4] [15]
validate experimental findings , mitigate contradictory information in the literature and reliably
address important issues such as product lifetimes and questions that are relevant to occupational and
public health.
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 20579-4:2018(E)
Surface chemical analysis — Guidelines to sample
handling, preparation and mounting —
Part 4:
Reporting information related to the history, preparation,
handling and mounting of nano-objects prior to surface
analysis
1 Scope
This document identifies information to be reported in a datasheet, certificate of analysis, report or
other publication regarding the handling of nano-objects in preparation for surface chemical analysis.
This information is needed to ensure reliability and reproducibility of analyses needed to advance
research and technology using these materials, and for obtaining appropriate understanding of
potential nano-object environmental and biological impacts. Such information is in addition to other
details associated with specimen synthesis, processing history and characterization, and should
become part of the data record (sometimes identified as provenance information) regarding the source
of the material and changes that have taken place since it was originated.
This document includes informative annexes that summarize challenges associated with nano-objects
that highlight the need for increased documentation and reporting in a material data record (Annex A)
and provide examples of methods commonly used to extract particles from a solution for surface
chemical analysis (Annex B). An example set of relevant sample data is shown in Annex C.
This document does not define the nature of instrumentation or operating procedures needed to ensure
that the analytical measurements described have been appropriately conducted.
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
regarding surface analysis and the following 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 http:// www .electropedia .org/
3.1
nanomaterial
material with any external dimension in the nanoscale (3.4) or having internal structure or surface
structure in the nanoscale
Note 1 to entry: This generic term is inclusive of nano-object and nanostructured material.
[SOURCE: ISO/TS 80004-1:2015, 2.4, modified – Note 2 to entry removed.]
3.2
nano-object
discrete piece of material with one, two or three external dimensions in the nanoscale (3.4)
Note 1 to entry: The second and third external dimensions are orthogonal to the first dimension and to each other.
[SOURCE: ISO/TS 80004-1:2015, 2.5]
3.3
nanoparticle
nano-object (3.2) with all external dimensions in the nanoscale (3.4) where the lengths of the longest
and the shortest axes of the nano-object do not differ significantly
Note 1 to entry: If the dimensions differ significantly (typically by more than three times), terms such as
nanofibre or nanoplate might be preferred to the term nanoparticle.
[SOURCE: ISO/TS 80004-2:2015, 4.4]
3.4
nanoscale
length range approximately from 1 nm to 100 nm
Note 1 to entry: Properties that are not extrapolations from a larger size are predominantly exhibited in this
length range.
[SOURCE: ISO/TS 80004-1:2015, 2.1]
3.5
provenance information
information that documents the history of the content information
Note 1 to entry: This information tells the origin or source of the content information, any changes that might
have taken place since it was originated, and who has had custody of it since it was originated.
Note 2 to entry: Examples of provenance information are the principal investigator who recorded the data, and
the information concerning its storage, handling and migration.
[SOURCE: ISO 13527:2010, 1.4.2, modified — Explanatory part of definition converted to Notes 1 and 2
to entry.]
4 Provenance information to be collected or retained regarding the history,
handling, storage and processing of nano-objects prior to submission for surface
analysis
4.1 Information record
Surface analysis of nano-objects is usually undertaken to collect important information at specific
stages during the lifetime or history of the material, such as after synthesis, before application
or testing, or after application or testing. Because of the susceptibility of nano-objects to change as
described in Annex A, it is important to retain as many relevant sample history and handling records
[3][16][17]
as available to maintain the provenance of the objects and data related to them. Information
regarding the preparation of samples for surface analysis, as described in Clause 5, and the results of
2 © ISO 2018 – All rights reserved

surface analysis of nano-objects become part of this information record that provides the history of
physical and chemical processes applied to a sample that would allow repetition of an experiment or
[18]
the reproducible use of the material for other applications . Appropriate information to be retained
and passed along with analysis information, as indicated by the examples in 4.2 and 4.3, can vary
depending on the history of the objects and the analysis objectives.
4.2 As-synthesized and as-prepared materials
Information about the nano-objects as synthesized or as prepared for application or property testing
should be retained in the information record. See Annex C for an example data set.
In addition to analysis data, such information should include:
a) Record of sample synthesis
Reference or details of synthesis as known (e.g. vendor, lot number, chemical sources, temperature).
(Subtle differences in process or initial chemicals can impact sample properties.)
EXAMPLE 1 Silver nanoparticles were produced by homogenous nucleation process via borohydride
reduction.
EXAMPLE 2 Bio-Clean XY particles were purchased from ABC Company and received month/year, lot
number 12345.
EXAMPLE 3 Single-layer graphene was grown on 25 µm 99,99 % pure Cu foil using chemical vapor
deposition with methane precursor. The graphene layers cover both sides of the Cu foil.
b) Important dates: synthesis, arrival in laboratory, opening of sample container, primary
measurements, expiry date.
EXAMPLE Silver nanoparticles were produced at XYZ University on December 12, 2012, and received at
TUW Laboratory on December 17, 2012, then placed in a dark refrigerator for storage. The sample container
was first opened on January 2, 2013. The sample was prepared for dynamic light scattering (DLS) analysis
by dilution in purified water (resistivity 18,2 MΩ·cm at 25 °C) on January 5 and the first DLS measurements
at TUW confirming size distribution were conducted on January 5, 2013. A set of particles were prepared for
electron microscopy on January 18, 2013, with images collected the same day. The sample appeared to be
stable with regard to size as observed by DLS measurements. However, it was observed to have agglomerated
[19]
and formed precipitates in April 2013 .
c) Storage time, conditions and containers (temperature, temperature variations, light shielded,
shipping or transport).
EXAMPLE 1 Sample was stored in refrigerator at 3 °C upon receipt.
EXAMPLE 2 Particles were stored in initial glass packaging at ambient room temperature in dark
conditions.
EXAMPLE 3 Initial suspension of particles was divided into five equal portions in new glass containers
and stored under refrigeration.
d) Additional processing (e.g. dried, washed, heated, sonicated or functionalized, including method
and number of times processed).
EXAMPLE 1 Dry particles were dispersed in a citrate saturated solution for storage. To assist dispersion,
50 ml of the particle suspension was sonicated for 30 min with bath/probe sonicator model 1A (effective
[17][20]
energy input Joules/litre, probe type, operation mode) at frequency 20 kHz .
[21]
EXAMPLE 2 Samples were removed from solution using the flash dry method .
EXAMPLE 3 Particles formed in nitrate solution were dispersed in citrate-saturated solution (or x M
solution if not saturated) to stabilize the suspension for short-term storage.
EXAMPLE 4 Graphene was transferred from 25 µm Cu foil onto NiTi stents using a 50 nm layer of
poly(methyl methacrylate) 4 % in anisole and etching in 0,5 M copper nitrate solution.
4.3 After testing, exposure, treatment or retrieval
Information related to characterization of nano-objects being examined after some type of testing,
environmental exposure or retrieval or after treatment by some type of deliberate or accidental process
(e.g. agglomeration as a result of solution exposure, oxidation or reduction based on the working
environment, coating formation or removal) should be retained in the information record.
Such information should include:
a) Information about the origin of the nano-objects, as noted in 4.1, before property testing or
environmental exposure.
EXAMPLE 1 Au nanoparticles stabilized in citrate were purchased from ABC Incorporated in July 2011
for toxicity testing.
EXAMPLE 2 Physicochemical characterization measurements of the particles used in this study were
conducted at 123 Laboratory in June 2013 and are summarized in report 123.
b) Record of the testing, exposure or sampling process prior to the planned measurements, including
dates of testing, sampling or processing, storage conditions and any processing before storage or
presentation for measurement not covered below.
EXAMPLE 1 Silver nanoparticles were suspended in cell culture media for 24 hours at 37 °C.
EXAMPLE 2 Iron nanoparticles were suspended in water containing CF for 6, 12, 24, 36 and 48 hours.
EXAMPLE 3 Carbon nanotubes were suspended in solvent QRX and sonicated (type of device, operating
conditions, effective energy input and time) for use in the formation of composite films.
5 Information to be reported related to preparing and mounting of
nanomaterials for surface chemical analysis
5.1 General
The methods of sample handling and storage in preparation for analysis described in ISO 20579-1 and
ISO 20579-2 will apply in many circumstances. Information about the following shall be provided as
part of the material information record.
5.2 Initial form or packaging of sample
The nature of the sample as received shall be described (e.g. dry powder, liquid suspension).
EXAMPLE 1 Material was received as dry powder in a sealed container with an argon atmosphere.
EXAMPLE 2 Particles were received in citrate solution at a concentration of X mg/ml.
5.3 Analysis objective or special requirements
The objectives of analysis or any special sample requirements shall be described (e.g. determine
thickness of an adsorbed layer, verify presence of a specific coating, determine the surface chemical
state, measure the particle shape or examine the state of particles after specific reaction time).
EXAMPLE XPS measurements were used to examine the nature of surface coatings on the particles and
determine the thickness of surface coatings.
5.4 Description of method used to prepare samples for analysis
A description of the procedure and any chemicals used to prepare the material for analysis shall be
included. Appropriate detail shall be provided to enable the procedure to be reproduced. It is sufficient
to provide a reference to a procedure that is available in the literature if that description meets this
4 © ISO 2018 – All rights reserved

criterion. (See Annex B for example methods, e.g. filtered from solution, washed three times in purified
water, dried in a vacuum desiccator, dispersed in biological or other media).
Depending on the initial form of sample and the requirements of the analysis method, an appropriate
sample preparation might be needed. Special attention needs to be paid to the dispersion of material,
especially for dispersion of powders in a liquid with a focus on the stability of the dispersion. Because
it can influence particle behaviour, the whole dispersion procedure, including fluid composition (water
or other solvent, content of dispersant aids) and specific energy input (e.g. stirring, mixing, ultrasound)
shall be described in detail. For particles in dispersions that need to be analysed in a dry state, the
opposite procedure is necessary: particles have to be separated from liquid, i.e. by centrifugation or
filtration, and washed, where appropriate (see Annex B). Again, the whole procedure shall be recorded.
EXAMPLE 1 Solution containing particles was washed three times using centrifugation and resuspended in
purified water (see Annex B).
EXAMPLE 2 Particles were removed from solution before XPS and TEM analysis by the flash drying process
[22]
described by Nurmi et al.
EXAMPLE 3 Particles received in a dry state were dispersed in media to break up agglomerates before
analysis.
5.5 Method of mounting sample for analysis (see ISO 20579-1 and ISO 20579-2 for
examples)
EXAMPLE 1 Dispersion of cleaned particles was deposited on a cleaned silicon wafer and dried in a laminar
flow cabinet with HEPA filter.
[23]
EXAMPLE 2 Drops of suspension containing nanoparticles were placed on a cleaned silicon wafer and dried
[24]
. Multiple deposits were made to fully cover the substrate.
Annex A
(informative)
Needs for enhanced documentation and application of surface
chemical analysis methods to assist in identifying and avoiding
artefacts and misinterpretations involving research and
applications of nano-objects
A.1 Overview of challenges
A.1.1 General
[4] [25]
In spite of the rapidly increasing numbers of publications , patents , and consumer and other
products associated with nanoscience and nanotechnology, there are important underlying issues
or challenges that need to be solved to enable nanotechnology to significantly impact some of the
biomedical, energy and environmental challenges that confront the world community. As indicated later
in this subclause, research papers, critical review articles, editorial perspectives and scientific press
[4][11][26-33]
news articles have highlighted a variety of issues associated with reproducible synthesis,
properties and characterization.
Fundamentally, the ability, or rather inability in many circumstances, to reproducibly supply
nanomaterials with repeatable and well-controlled properties impact, in many cases, the ability
to manufacture, process and store nano-objects as well as the shelf life and functional lifetime of
‘products’ that use them. These issues affect the ability to reliably design new materials and systems as
well as determine the impact of nano-objects on health and safety as they undergo transformations in
the environment and in biological systems. These characteristics of nano-objects present challenges to
safety testing.
ISO TC 229 has prepared guidance on physico-chemical characterization of engineered nanomaterials
[34]
for toxicological assessment and the OECD has prepared a document dealing with sample preparation
[17]
and dosimetry for safety testing of manufactured nano-objects . The document discusses many
issues identified in this annex (and others) and highlights the importance of recording a wide variety of
information as identified in this document.
Publication titles highlighting challenges associated with nanoscience and nanotechnology:
— ‘Identification and Avoidance of Potential Artifacts and Misinterpretations in Nanomaterial
Ecotoxicity Measurements’ (Reference [27] Peterson);
— ‘Nanosafety Research – Are we on the Right Track?’ (Reference [32] Krug);
— ‘Common pitfalls in nanotechnology: lessons learned from NCI’s Nanotechnology Characterization
Laboratory’ (Reference [26] Crist);
— ‘Discriminating the states of matter in metallic nanoparticle transformations: What are we missing?’
(Reference [29] Pettibone);
— ‘The characterization bottleneck’ (Reference [31] Richmond);
— ‘Nanobiomaterials and nanoanalysis: Opportunities for improving the science to benefit biomedical
technologies.’ (Reference [11] Grainger);
— ‘The potential toxicity of nanomaterials – The role of surfaces’ (Reference [30] Karakoti).
6 © ISO 2018 – All rights reserved

In the context of this document, many critical concerns can be grouped into three areas:
i) synthesis details, including precursor details and sources;
ii) importance of surfaces and interfaces;
iii) time and environmentally induced material changes or transformations.
The issues raised in these areas can be fully or partially addressed by a) improved recording and
reporting details of sample history and processing, information often missing in current reports and
b) applying an expanded, but appropriate, range of characterization methods that can verify material
consistency or identify the nature of material changes.
An ISO technical report providing an overview of characterization methods for graphene is being
[35]
prepared and a review of specific characterization methods important to graphene is available .
Surface chemical analysis tools are much needed characterization tools, but for surface and other
analysis methods to be of most value requires i) relevant information about the methods used to create
and process the materials before the analysis (sample history) and ii) knowledge of how the material
was prepared or processed for the analysis.
A.1.2 Synthesis details
The literature contains many examples of ‘identical’ nanoparticles for which very different behaviours
have been demonstrated. Such differences can be caused by minor variations in the synthesis method
[15][36]
or processing of the materials . Careful research has reported difficulties with reproducing well-
[15][22] [22]
defined nanoparticles using the same detailed and careful processes . Francia et al. described
challenges in the preparation of core-shell nanoparticles. Samples prepared by the same experienced
chemist, using the same identical equipment and the same lots of reagents, showed significant batch-to-
batch variation in both the percentage composition and surface chemistry of the nanoparticles. Without
analytical measurements of the surface chemistry on these particles, the differences would have gone
unrecognized and the causes of the inconsistency of results would have been unknown.
Discussions with commercial vendors suggest they can face similar issues because a synthesis process
used for years seems to ‘drift’ with time and particle properties produced by the same well-documented
process might produce particles with differing properties. Careful technical records of procedure (and
the person executing it), storage times and conditions, and processing, as well as measurements that
can assist identification of particle variations, are needed, together with the development of ‘failure’
margins for quality assurance of ‘batch-to-batch’ reproducibility.
A.1.3 Importance of surfaces and interfaces
Because surface or interfacial atoms make up a large fraction of the total atoms in nanomaterials,
surfaces and interfaces can have a major impact on the properties of nano-objects. Particle surfaces
usually include deliberate or environmentally induced coatings. Both inconsistency of deliberate
[22]
coatings, such as reported by Francia et al. , or the presence of unplanned elements or coatings
[4]
(such as fluorine on a copper oxide particle ) can cause unexpected problems. Often the presence of
an unexpected coating or surface element is not readily detected without the use of specific surface-
sensitive analysis tools. The type of information that can be obtained by surface analysis tools has been
[11][4][9][37-41]
highlighted .
A.1.4 Time and environmentally induced change
In many circumstances, nano-objects are unstable and can change with time or alter when the
[15][42][43] [26]
environment is changed . Crist et al. and others note that purchased nanoparticles
frequently have properties significantly altered from those supposedly provided by the manufacturer.
In most cases the particles might have had the desired properties initially, but during storage, handling,
processing and sometimes upon dispersion into desired media these properties change.
A.2 Three elements critical to materials consistency
A.2.1 General
Because of the importance of synthesis, surfaces and time, reproducible and reliable delivery of
nanomaterials for a wide variety of applications requires three components:
i) following highly consistent procedures during synthesis and handling;
ii) recording and reporting records of times, temperatures and chemicals used during synthesis,
processing and storage, all to be able to verify and trace process consistency and material
history; and
iii) application of the appropriate characterization tools to verify material composition and consistency
and to rule out other surprises that impact material properties.
A.2.2 Challenges associated with preparing particles for analysis
The risk of particle alterations induced by changes in the particle environment and possible introduction
of surface and other contamination make it necessary to develop appropriate procedures for preparing
particles for analysis. Many nanoparticles are suspended in solution while characterization methods can
require dry particles either in a gaseous environment or possibly in vacuum. A variety of methods (see
Annex B) have been applied to prepare particles for analysis while retaining the desired information.
The methods used to prepare a material are critical to the analysis and should be reported together
with the results.
In some cases, nano-objects which were originally delivered as a powder are likely to be agglomerated,
and have to be dispersed in a liquid prior to analysis (see B6), for example in single-particle surface
analysis using scanning Auger microscopy (SAM) or for deposition on a surface for scanning probe
analysis. A specific power input might be necessary for dispersion, i.e. by using ultrasound, and might
also lead to changes of surface properties or add impurities. For an appropriate interpretation of
collected data the whole preparation procedure needs to be carefully considered and described in detail.
A.2.3 Recommendations for synthesis and characterization of nano-objects
The importance of extreme care in nanoparticle synthesis and processing cannot be overemphasized.
Based on experiences of a variety of users, a general set of recommendations for nanoparticle synthesis
[4]
and analysis has been suggested . Elements of these recommendations address in various ways the
issues and challenges noted above. These might be addressed in other ways, but this list shows how
some of the challenges have been addressed.
1) Plan and organize the experiment to minimize and hold constant the number of parameters
that can vary in the process. Without adequate planning and records, the process and particle
properties will usually change with each different operator and over time. The specific location
or facilities used within a laboratory, for example different clean hoods, sources of water, source
and age of precursor chemicals, have all been attributed to variations in material characteristics,
emphasizing an importance of consistency and careful documentation.
2) Emphasis should be given to careful cleaning of glassware or other synthesis components (e.g.
from instruments or autoclave) and storage containers as described more fully in B.7. Several
oxidizing and/or reducing agents are available commercially for cleaning glassware. If the synthesis
is carried out on a routine basis, it is advisable to purchase dedicated glassware and instruments
for a particular type of nanomaterial to avoid cross-contamination. It has been found that in some
circumstances scratches on used glassware or detergent residue from cleaning can cause synthesis
issues and new or disposable glassware might be required.
3) In common practice, a master batch of nanoparticles should be stored separately and small aliquots
are taken from the batch when required for characterization. However, the repeated opening of
the master batch of nanoparticles suspension/powder to ambient atmospheres is not desirable
and can be a source of contamination. Repeated use of a spatula or pipette tips in the master
8 © ISO 2018 – All rights reserved

batch should also be avoided to minimize contamination. It is suggested that instead of storing
the nanoparticles sample in one master batch, the material should be stored in several small, pre-
cleaned vials, ideally under an argon atmosphere. Such storage will minimize repeated exposure of
the entire sample to the ambient environment. If surface oxidation or chemical state information is
important, once exposed to the environment, a vial should not be used for surface characterization
studies, although characterization of bulk properties could still be done on the samples from the
same vial.
4) Seemingly harmless instruments, such as pH, conductivity or temperature probes, can introduce
contamination and should be cleaned thoroughly before placing in contact with the batch of nano-
objects. Sonication can also damage a sample due to heating and particle collisions. The exposure
of a master batch of nano-objects to probes should be avoided if possible; instead, smaller aliquots
taken out of the master batches should be used for measurement.
5) The storage conditions for nano-objects should also be considered. General experience suggests
that storage conditions, such as light, dark, temperature (room temperature, refrigerated or
frozen), humidity, gaseous atmosphere composition (i.e. air vs vacuum vs dry nitrogen vs argon)
and duration of storage, can affect the stability and reactivity of nano-objects. For example,
solutions of well-dispersed nanoparticles occasionally cannot be resuspended after they have been
subjected to seemingly innocuous storage conditions such as having been frozen once or stored at
room temperature under nitrogen.
6) Researchers synthesizing nano-objects for biological applications should treat them as a biological
sample. It is advisable for materials and biological scientists to work together in order to understand
the nuances of process parameters and how the process can influence the biological end-points. All
nano-objects used in biological studies should be handled analogously to live biological samples
and the contamination from various sources, such as bare hands, glassware, hoods or workbenches,
should be minimized. All glassware and workbenches should be sterilized and the researchers
should use good laboratory practices (GLPs), lab-recorded standard operating protocols (SOPs),
sterilized tips and glassware, and personal protective equipment (PPE) for materials synthesis.
7) Select an appropriate core set of characterization tools and established analytical protocols
with quality control criteria for batch failure (including a surface-sensitive method) to verify
the repeatability and consistency of the synthesis approach.
8) Records related to chemicals used in synthesis, dates of synthesis and means of storage should
be kept and linked to samples, as well as to batches of samples, so the parentage and history of
materials can be maintained and possible similarities and sources of differences can be tracked if
they are identified. Time intervals between synthesis and use or characterization should be
recorded and reported.
Annex B
(informative)
Example methods for extraction of nano-objects from solution for
surface analysis and issues for dispersion of dry particles
B.1 Overview
The preparation protocols of nanomaterials for their analysis are determined by the nature of the
nanoparticles being examined, the questions being asked and the analysis method being applied.
As noted in A.2.2, many nanoparticles are prepared, stored, processed or used while dispersed in a
solution of some type. For the application of vacuum-based surface-analysis methods, and some
other types of sample testing and uses, it is necessary to extract particles from solution, retaining as
much of the desired information as possible. In contrast, other particles are produced or received in
dried conditions, often in the form of aggregates. For some applications or to enable some types of
measurements, additional sample treatments are necessary to disperse these particles and break up
agglomerated particles as close to the primary particle size as possible. In some cases it can be desirable
to disperse particles in a liquid before depositing them on a substrate for analysis. Particle dispersion
presents its own set of challenges.
One challenge in preparing solution-dispersed particles for surface analysis occurs because
nanoparticles in solution are usually surrounded by a complex mixture of ions and organic molecules
[44]
(Figure B.1) . Ions attached to the particle are often of importance for the analysis, while other
molecules and ions surrounding the particles are not usually of primary interest. Careful experimental
protocols are often
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