ISO/TS 10868:2017

TECHNICAL ISO/TS
SPECIFICATION 10868
Second edition
2017-05
Nanotechnologies — Characterization
of single-wall carbon nanotubes using
ultraviolet-visible-near infrared (UV-
Vis-NIR) absorption spectroscopy
Nanotechnologies — Caractérisation des nanotubes à simple couche
de carbone par utilisation de la spectroscopie d’absorption UV-Vis-NIR
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
4 Principle . 2
4.1 General . 2
4.2 UV-Vis-NIR absorption spectroscopy . 2
4.3 Optical absorption peaks of SWCNTs in the UV-Vis-NIR region . 2
4.4 Relation between SWCNT diameter and optical absorption peaks . 4
4.5 Derivation of the purity indicator from optical absorption peak areas . 4
4.6 Derivation of ratio of metallic SWCNTs from optical absorption peak areas . 6
5 UV-Vis-NIR spectrometer . 6
6 Sample preparation method . 6
6.1 General . 6
6.2 Preparation of D O dispersion for measurement of mean diameter and the ratio of
metallic SWCNTs . 7
6.3 Preparation of solid film dispersion for measurement of the mean diameter and
the ratio of metallic SWCNTs . 7
6.4 Preparation of DMF dispersion for determination of the purity indicator . 8
7 Optical measurement procedures and conditions . 8
8 Data analysis and results interpretations . 9
8.1 Data analysis for characterization of SWCNT diameter. 9
8.2 Data analysis for determination of the purity indicator . 9
8.3 Data analysis for characterization of the ratio of metallic SWCNTs . 9
9 Measurement uncertainties . 9
10 Test report .10
Annex A (informative) Case study for derivation of the relation between optical absorption
peaks of SWCNTs and their mean diameter .11
Annex B (informative) Case study for determination of the purity indicator .16
Bibliography .19
Foreword
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This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
This second edition cancels and replaces the first edition (ISO/TS 10868:2011), which has been
technically revised.
iv © ISO 2017 – All rights reserved

TECHNICAL SPECIFICATION ISO/TS 10868:2017(E)
Nanotechnologies — Characterization of single-wall carbon
nanotubes using ultraviolet-visible-near infrared (UV-Vis-
NIR) absorption spectroscopy
1 Scope
This document provides guidelines for the characterization of compounds containing single-wall
carbon nanotubes (SWCNTs) by using optical absorption spectroscopy.
The aim of this document is to describe a measurement method to characterize the diameter, the purity,
and the ratio of metallic SWCNTs to the total SWCNT content in the sample.
The analysis of the nanotube diameter is applicable for the diameter range from 1 nm to 2 nm.
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/TS 80004-4, Nanotechnologies — Vocabulary — Part 4: Nanostructured materials
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO/TS 80004-4 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1 Terms and definitions
3.1.1
purity indicator
optically defined indicator of the ratio of the mass fraction of SWCNTs to the total carbonaceous content
in a sample
Note 1 to entry: Purity indicator is NOT “purity” itself which is defined as the percentage of mass of SWCNTs to
the total mass of the sample. This guideline cannot evaluate this general purity because absorption spectroscopy
cannot detect metallic impurities that are generally contained in any SWCNT sample. In order to characterize
metal impurity content, there is a different Technical Specification on thermogravimetric analysis. Metallic
impurity is defined as catalytic metal particle and does not include metallic carbon nanotube. See ISO TS 11308.
3.1.2
ratio of metallic SWCNTs
optically defined compositional ratio of metallic SWCNTs to the total SWCNTs contained in the sample
3.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
CMC Sodium carboxymethylcellulose
DMF Dimethylformamide
DOS Density of states
NIR Near infrared
NMP N-Methyl-2-Pyrrolidone
SC Sodium cholate
DOC Sodium Deoxycholate
SDS Sodium dodecyl sulfate
SDBS Sodium dodecylbenzene sulfonate
SWCNT Single-wall carbon nanotube
TEM Transmission electron microscope
UV Ultraviolet
VHS van Hove singularity
Vis Visible
4 Principle
4.1 General
All SWCNT samples contain both semiconducting and metallic SWCNTs, together with impurities
consisting of carbon and other elements unless the samples have been altered after production. UV-
Vis-NIR absorption spectroscopy can be used for the measurement of interband optical transitions
specific to SWCNTs. The analysis of these optical transitions provides qualitative and semiquantitative
information important for the characterization of SWCNT samples, such as mean diameter, purity, and
the ratio of metallic SWCNTs to the total SWCNT content.
4.2 UV-Vis-NIR absorption spectroscopy
The intensity of light passing at a specified wavelength, λ, through a specimen (I) is measured and it
is compared to the intensity of light before it passes through the specimen (I ). The ratio I/I is called
0 0
a transmittance. The absorbance, A, is expressed as −log (I/I ). The plot of the absorbance against
wavelength for a particular compound is referred to as an absorption spectrum.
NOTE The relationship between transmittance and absorbance is only rigorously correct when reflectance
is negligible and there is no scattering.
4.3 Optical absorption peaks of SWCNTs in the UV-Vis-NIR region
The shape of the electronic DOS of semiconducting and metallic SWCNTs shown in Figure 1 is a series
of spikes that are referred to as VHS. The peaks observed in the optical absorption spectra of SWCNTs
are attributed to the electronic transitions between these VHSs as shown by arrows in Figure 1. S
and S are used as the symbols of the absorption due to the first and second interband transitions of
2 © ISO 2017 – All rights reserved

semiconducting SWCNTs, respectively [see Figure 1 a)]. M means the absorption arising from the first
interband transition of metallic SWCNTs [see Figure 1 b)].
a) Electronic DOS of semiconducting SWCNTs b) Electronic DOS of metallic SWCNTs
Key
X energy (eV)
Y electronic DOS (arbitrary unit)
S first interband optical transition attributed to semiconducting SWCNTs
S second interband optical transition attributed to semiconducting SWCNTs
M first interband optical transition attributed to metallic SWCNTs
NOTE 1 Arrows represent interband transitions that result in optical absorption.
NOTE 2 See Reference [2].
Figure 1 — Electronic DOS diagram of SWCNTs near the Fermi level
To interpret the absorption spectra of SWCNTs, band structures calculated using the zone-folding
method are frequently used. The electronic structure of an SWCNT is generally given by that of a two-
[2]
dimensional graphite sheet expressed by the tight binding approximation as shown in Formula (1) :
12/
 
  ka ka
   
3ka
yy
x 2
E =± γ 14± cosc  os +4cos  (1)
   
2D
     
22 2
 
     
 
where
is the two dimensional energy dispersion relation for a single graphene sheet;
E
2D
[3]
a is the lattice parameter ;
are the components of the reciprocal unit vector;
k and k
x y
γ is the overlap integral.
...