Table Of ContentSS 643 : Part 2 : 2019
(ICS 07.120; 59.100.20)
SINGAPORE STANDARD
Structural characterisation of graphene flakes -
Part 2: Determination of lateral size of graphene
flakes by optical microscopy
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SS 643: Part 2: 2019
(ICS 07 .120; 59.100.20)
SINGAPORE STANDARD
Structural characterisation of graphene flakes -
Part 2: Determination of lateral size of graphene
flakes by optical microscopy
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ISBN 978-981-48-3565-7
55 643: Part 2 : 2019
This Singapore Standard was approved on 20 March 2019 by the Chemical Standards Committee
under the purview of the Singapore Standards Council.
First published 2019.
The Chemical Standards Committee, appointed by the Standards Council, consists of the following
members:
Name Capacity
Chairman Dr Keith Carpenter Individual Capacity
Deputy
Chairman Er. Lucas Ng Individual Capacity
Secretary 1 Ms Elane Ng Standards Development Organisation@Singapore
Chemical Industry Council
Secretary 2 Ms Rosmalinda Tay Standards Development Organisation@Singapore
Chemical Industry Council
Members Mr Goh Tiak Boon Individual Capacity
Prof Alfred Huan Individual Capacity
Mr Khong Beng Wee Individual Capacity
Mr Terence Koh Singapore Chemical Industry Council Limited
Dr Leong Kwai Yin Individual Capacity
Dr Thomas Liew National Metrology Centre
Mr Alan Lim Maritime and Port Authority of Singapore
Mr Lim Eng Kiat Individual Capacity
Mdm Jamie Lim Ministry of Manpower
Mr Lim Kian Chye / Housing & Development Board
Mr Ng Eng Fu
Prof Loh Kian Ping National University of Singapore
Dr Loh Wah Sing Individual Capacity
Ms Pamela Phua Singapore Paint Industry Association
Mr Seah Khen Hee Individual Capacity
A/Prof Timothy Tan Nanyang Technological University
Dr Teo Tang Lin Chemical Metrology Division, Health Sciences
Authority
Ms Suzanna Yap National Environment Agency
Co-opted
Members Ms Christina Loh Individual Capacity
Mr Pitt Kuan Wah Individual Capacity
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55 643: Part 2 : 2019
The Technical Committee on Nanotechnology, appointed by the Chemical Standards Committee and
responsible for the preparation of this standard, consists of representatives from the following
organisations:
Name Capacity
Chairman Prof Alfred Huan Individual Capacity
Deputy
Chairman A/Prof Lanry Yung Individual Capacity
Secretary Ms Rosmalinda Tay Standards Development Organisation@Singapore
Chemical Industry Council
Members Dr Hengky Chang Nanyang Polytechnic
Dr Paul Chiew Agri-Food and Veterinary Authority of Singapore
Er. Veronica Chow Ministry of Manpower
A/Prof Duong Hai Minh National University of Singapore
Mr Foo Toon Fong GLOBALFOUNDRIES Singapore Pte Ltd
Dr Thomas Liew National Metrology Centre
Dr Lim Mong Hoo PUB, Singapore's National Water Agency
Dr Lerwen Liu NanoGlobe Pte Ltd
A/Prof Ng Kee Woei National Technological University
Ms Pamela Phua AkzoNobel Paints
Dr Allen Poh Ministry of the Environment and Water Resources
Mr Sachin Gupta Rolls-Royce Singapore Pte Ltd
Dr Junie Tok P & G International Operations Pte Ltd
Ms Suzanna Yap National Environment Agency
Dr Yow Soh Zeom Health Sciences Authority
Co-opted
Members Dr Kurnia Wira Individual Capacity
Dr Leong Yew Wei Individual Capacity
Prof Ong Wei-Yi Individual Capacity
Dr Ramam Akkipeddi Individual Capacity
Dr Sanjay Thakur Individual Capacity
The Working Group on Graphene, appointed by the Technical Committee to assist in the preparation
of this standard, comprises the following experts who contribute in their individual capacity:
Name
Co-Convenors Dr Ricardo Vinicius Oliveira
Dr Ramam Akkipeddi
Secretary Ms Rosmalinda Tay
Members Dr Fan Rongli
Mr Ng Chun Tat
Dr Vitali Lipik
Dr Yu Shengkai
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55 643: Part 2 : 2019
The organisations in which the experts of the Working Group are involved are:
Housing & Development Board
Institute of Materials Research and Engineering
National Metrology Centre
NUS Centre for Advanced 20 Materials and Graphene Research Centre
PUB, Singapore's National Water Agency
Sportmaster
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55 643: Part 2 : 2019
Contents
Page
Foreword_______________________________ 6
0 Introduction 7
1 Scope 7
2 Normative references 7
3 Terms and definitions 8
4 Principle 9
5 Apparatus 9
6 Procedure 10
7 Uncertainties 12
8 Test report 12
Figures
1 A typical image of the graphene flakes testing sample, its binary base and the size
distribution chart_________________________ 11
2 Cumulative distribution curve of flake size in the measured flakes 11
- - - - - - - -
Bibliography ____________________________ 13
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55 643: Part 2 : 2019
Foreword
This Singapore Standard was prepared by the Working Group on Graphene appointed by the Technical
Committee on Nanotechnology under the purview of the Chemical Standards Committee.
SS 643 consists of the following four parts, under the general title, 'Structural characterisation of
graphene flakes':
Part 1: Methods and sample preparation
Part 2: Determination of lateral size of graphene flakes by optical microscopy
Part 3: Determination of level of defects on graphene flakes by Raman spectroscopy
Part 4: Determination of number of layers in graphene flakes by atomic force microscopy
Part 1 is essential for the implementation of the standard and is used with Parts 2, 3 or 4.
In preparing this standard, reference was made to the following publications:
ISO 18466:2016 Stationary source emissions - Determination of the biogenic fraction
in CO2 in stack gas using the balance method
ISO/TS 80004-13:2017 Nanotechnologies - Vocabulary - Part 13: Graphene and other two
dimensional materials
Acknowledgement is made for the use of information from the above publications.
This standard is expected to be used by manufacturers, buyers, users and testing laboratories involved
in the production and commercialisation of graphene, academia and IHLs in Singapore which have
formed the nanotechnology research entities, relevant regulatory bodies and conformity assessment
bodies.
Attention is drawn to the possibility that some of the elements of this Singapore Standard may be the
subject of patent rights. Enterprise Singapore shall not be held responsible for identifying any or all of
such patent rights.
NOTE
1. Singapore Standards (SSs) and Technical References (TRs) are reviewed periodically to keep abreast of
technical changes, technological developments and industry practices. The changes are documented through the issue of
either amendments or revisions.
2. An SS or TR is voluntary in nature except when it is made mandatory by a regulatory authority. It can also be cited in
contracts making its application a business necessity. Users are advised to assess and determine whether the SS or TR is
suitable for their intended use or purpose. If required, they should refer to the relevant professionals or experts for advice
on the use of the document. Enterprise Singapore shall not be liable for any damages whether directly or indirectly suffered
by anyone or any organisation as a result of the use of any SS or TR.
3. Compliance with a SS or TR does not exempt users from any legal obligations.
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Structural characterisation of graphene flakes -
Part 2: Determination of lateral size of graphene flakes by optical
•
microscopy
O Introduction
Graphene is a single layer of carbon atoms with each atom bound to three neighbours in a honeycomb
structure [1]. Since its discovery in 2004 by two researchers at the University of Manchester, graphene
has been considered a wonder material with the potential to revolutionise industrial sectors, from
coatings and composites to electronics and aerospace, due to its properties such as mechanical
strength, high electrical and thermal conductivity, flexibility, impermeability, etc. The estimated global
market for graphene is expected to reach a minimum of $500 million by 2025 [2].
However, as in the case of any other revolutionary material, the development of these applications and
their introduction into the market strongly depends on the quality of the graphene. There are currently
no established international or national standards for graphene although there is currently ongoing work,
detailed in ISO/TC 229 Nanotechnologies and IEC/TC 113 Nanotechnology for e/ectrotechnica/
products and systems. The lack of an established standard leads to a plethora of producers selling
"graphene products" which are essentially fine graphite, and not appropriate for the applications
mentioned above.
The development of this Singapore Standard will help to provide manufacturers and users with standard
methods for the characterisation of graphene. In addition, this standard is intended to be used to obtain
certification of graphene materials.
1 Scope
This part of the standard specifies the principles and procedure for assessing the lateral size of
graphene flakes using optical microscopy. The use of this technique helps to evaluate lateral size,
shape and size distribution of graphene flakes, based on the variation of relative intensity of reflected
light from the sample.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
SS 643 : Part 1 Structural characterisation of graphene flakes - Part 1: Methods and
sample preparation
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3 Terms and definitions
For the purpose of this Singapore Standard, the following terms and definitions apply.
3.1 2D material
Material, consisting of one or several layers (3.9) with the atoms in each layer strongly bonded to
neighbouring atoms in the same layer, which has one dimension, its thickness, in the nanoscale or
smaller and the other two dimensions generally at larger scales
NOTE 1 to entry - The number of layers when a two-dimensional material becomes a bulk material varies
depending on both the material being measured and its properties. In the case of graphene layers, it is a two
dimensional material up to 10 layers thick for electrical measurements, beyond which the electrical properties of
the material are not distinct from those for the bulk [also known as graphite (3.8)].
NOTE 2 to entry - Interlayer bonding is distinct from and weaker than intralayer bonding.
NOTE 3 to entry - Each layer may contain more than one element.
NOTE 4 to entry - A two-dimensional material can be a nanoplate.
3.2 Few-layer graphene (FLG)
Two-dimensional material consisting of three to ten well-defined stacked graphene layers
3.3 Graphene (G)
Single layer of carbon atoms with each atom bound to three neighbours in a honeycomb structure
3.4 Graphene flake
A small, flat, very thin piece of graphene material that has broken away or been peeled off from a
graphite crystal, consisting of either graphene (G), graphene oxide (GO) or reduced graphene oxide
(rGO) layers.
NOTE - Graphene flakes typically have 10 layers or less with lateral dimensions ranging from 500 nm to 100 µm.
3.5 Graphene nanoplate I Graphene nanoplatelet (GNP)
Consisting of graphene layers
NOTE to entry - GNPs typically have thickness of between 1 nm to 3 nm and lateral dimensions ranging from
approximately 100 nm to 100 µm
3.6 Graphene oxide (GO)
Chemically modified graphene prepared by oxidation and exfoliation of graphite, causing extensive
oxidative modification of the basal plane
NOTE to entry - Graphene oxide is a single-layer material with a high oxygen content, typically characterised by
C/0 atomic ratios less than 3.0 and typically closer to 2.0.
3. 7 Graphite
Allotropic form of the element carbon, consisting of graphene layers stacked parallel to each other in a
three-dimensional, crystalline, long-range order
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3.8 Lateral size
flake size
<2D material> lateral dimensions of a 2D material nake
NOTE to entry - If the flake is approximately circular then this is typically measured using an equivalent circular
diameter or if not via x, y measurements along and perpendicular to the longest side
3.9 Layer
Discrete material restricted in one dimension, within or at the surface of a condensed phase
3.10 Optical microscopy (OM)
Method that uses visible light to acquire a magnified image of sample
Fastest and most convenient tool in basic research laboratories to evaluate graphene specimens. The
interaction between the visible light and the silicon oxide surface layer produces a good contrast for
graphene detection, making it possible to evaluate the size of the crystallite.
3.11 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/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
oxygen containing functional groups will remain and not all sp3 bonds will return back to sp2 configuration. Different
reducing agents will lead to different carbon to oxygen ratio and different chemical compositions in reduced
graphene oxide.
3.12 Sample preparation
All the actions taken to obtain representative analyses, samples or test portions from the original sample
4 Principle
Optical microscopy is used to observe graphene flakes. The testing sample (prepared in part 1) can
induce a contrast with the microscope light source to make the flakes visible, but this contrast may not
be obvious for a single layer graphene. The difference in the number of layers causes a colour shift in
the violet silicon oxide 300 nm layer pattern. An appropriate filter can maximise the image contrast as
a function of the incident wavelength and the oxide thickness. The contrast increases linearly with the
sample thickness for few layers, with changes in phase and amplitude for thicker samples (>6 layers)
shifting towards a higher wavelength and occurring as a negative contrast because the graphene
specimen can be brighter than the silicon oxide surface.
5 Apparatus
The apparatus required includes an optical microscope operating in the reflection mode, objective lens
magnification of 1 00x, computer and software for image acquisition.
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