1、 ISO 2017 Nanotechnologies Characterization of single-wall carbon nanotubes using ultraviolet-visible-near infrared (UV- Vis-NIR) absorption spectroscopy Nanotechnologies Caractrisation des nanotubes simple couche de carbone par utilisation de la spectroscopie dabsorption UV-Vis-NIR TECHNICAL SPECIF
2、ICATION ISO/TS 10868 Reference number ISO/TS 10868:2017(E) Second edition 2017-05 ISO/TS 10868:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or util
3、ized 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 ISOs member body in the country of the requester. ISO copyrig
4、ht office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/TS 10868:2017(E)Foreword iv 1 Scope . 1 2 Normative references 1 3 T erms, definitions and abbr e viat ed t erms 1 3.1 Terms and definitions . 1 3.2 A
5、bbreviated 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 are
6、as . 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 2 O dispersion for measurement of mean diameter and the ratio of metallic SWCNTs 7 6.3 Preparation of solid film dis
7、persion 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 SW
8、CNT 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
9、of SWCNTs and their mean diameter 11 Annex B (informative) Case study for determination of the purity indicator 16 Bibliography .19 ISO 2017 All rights reserved iii Contents Page ISO/TS 10868:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of natio
10、nal 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. Internati
11、onal 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 intende
12、d 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 .i
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15、 meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .org/ iso/ foreword .html. This document was pre
16、pared 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
17、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 des
18、cribe 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
19、 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 Voc
20、abulary Part 4: Nanostructured materials 3 T erms, d efinitions and abbr e viat ed t erms 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:
21、 IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp 3.1 T erms and definiti ons 3.1.1 purity indicator optically defined indicator of the ratio of the mass fraction of SWCNTs to the total carbonaceous content in
22、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
23、 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 opt
24、ically defined compositional ratio of metallic SWCNTs to the total SWCNTs contained in the sample ISO 2017 All rights reserved 1 ISO/TS 10868:2017(E) 3.2 Abbreviated terms For the purposes of this document, the following abbreviated terms apply. CMC Sodium carboxymethylcellulose DMF Dimethylformamid
25、e 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
26、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 tr
27、ansitions 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 spe
28、ctroscopy The intensity of light passing at a specified wavelength, , through a specimen (I) is measured and it is compared to the intensity of light before it passes through the specimen (I 0 ). The ratio I/I 0is called a transmittance. The absorbance, A, is expressed as log (I/I 0 ). The plot of t
29、he 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-N
30、IR 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 Fi
31、gure 1. S 11and S 22are used as the symbols of the absorption due to the first and second interband transitions of 2 ISO 2017 All rights reserved ISO/TS 10868:2017(E) semiconducting SWCNTs, respectively see Figure 1 a). M 11means the absorption arising from the first interband transition of metallic
32、 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 11 first interband optical transition attributed to semiconducting SWCNTs S 22 second interband optical transition attributed to semiconducti
33、ng SWCNTs M 11 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
34、structures calculated using the zone-folding method are frequently used. The electronic structure of an SWCNT is generally given by that of a two- dimensional graphite sheet expressed by the tight binding approximation as shown in Formula (1) 2 : (1) whereE is the two dimensional energy dispersion r
35、elation for a single graphene sheet;a is the lattice parameter 3 ;k x and k y are the components of the reciprocal unit vector; is the overlap integral. ISO 2017 All rights reserved 3 ISO/TS 10868:2017(E) 4.4 Relation between SWCNT diameter and optical absorption peaks Within a simple tight-binding
36、theory, in which the electronic band structure is assumed to arise from a pure p-orbital at each conjugated carbon atom, the low-energy band gap transitions take a simple analytical form. The energy gaps corresponding to the electron transitions are given by Formula (2) to Formula (4): (2) (3) (4) w
37、here E g (S 11 ), E g (S 22 ), E g (M 11 ) are the energy gaps corresponding to the transitions of S 11 , S 22and M 11 , respectively; d is the diameter of SWCNTs 4 . Formula (2) to Formula (4) show a simple relationship between the diameter and the optical transition energies (and thus the peak wav
38、elengths). This allows the estimation of the mean diameter of a SWCNT sample by the analysis of the absorption spectra originating from the optical transitions between VHSs. Formula (2) to Formula (4) can give information related to the diameter within some limitations. One of the limitations is tha
39、t the analysed peak(s) needs to be clearly resolved. 4.5 Derivation of the purity indicator from optical absorption peak areas As mentioned in 4.3, there are the specific absorptions of SWCNTs originating from interband transition between VHSs. These absorption peaks are typically observed in the Vi
40、s-NIR region. On the other hand, in the UV region, most SWCNT samples present optical absorption with the peak at 200 nm to 300 nm 5 . This absorption is attributed to the collective excitations of electron systems ( -plasmons) and can also be observed in most graphitic compounds 5 . Therefore, the
41、-plasmon absorption observed in most SWCNT samples is due to both SWCNTs and carbonaceous impurities. The -plasmon absorption is extremely broad and is superposed on the above-mentioned specific absorption of SWCNTs as a featureless background extending to the Vis-NIR and IR region. To summarize, th
42、e absorption spectrum of SWCNT samples in the Vis-NIR region is composed of the interband transitions of semiconducting and metallic SWCNTs and -plasmon absorbance (see Figure 2).4 ISO 2017 All rights reserved ISO/TS 10868:2017(E) Key X photon energy (eV) Y absorbance (absorbance unit) NOTE The rela
43、tive contribution from each component is arbitrary and also has differing chiral angle distributions. Figure 2 Typical UV-Vis-NIR absorption spectrum of an SWCNT sample 6 In Figure 2, the absorption from S nnand M 11gives rise to the absorption peak areas, AA(S nn ) and AA(M 11 ), and that of -plasm
44、on as AA( ). In addition, the total absorption AA(S nn )+ AA() or AA(M 11 )+AA( ) is designated as AA t (see Annex B). As long as samples of concern have similar mean diameters and diameter distributions, the relative magnitude of AA(S nn ) or AA(M 11 ) to AA tcan be used as an indicator of purity,
45、P i (S nn ) or P i (M 11 ) 78 , which is given by Formula 5: (5) Formula 5 gives information related to purity within some limitations. One of the limitations is that the analysed peak(s) needs to be clearly resolved. Another is that samples need to have almost similar mean diameters and distributio
46、ns as determined by the locations of the peak positions. NOTE Surfactants and/or dispersing agents could also add complexity to the spectra. ISO 2017 All rights reserved 5 ISO/TS 10868:2017(E) 4.6 Derivation of ratio of metallic SWCNTs from optical absorption peak areas On the basis of the analogy o
47、f 4.5, an analysis of the area under the peak for semiconducting and metallic SWCNTs provides an indicator of the ratio of metallic SWCNTs to the total SWCNTs, which is given by Formula (6): (6) Furthermore, Formula (6) can be converted into Formula (7) for R Metalas the function of AA(S 22 ) and AA
48、(M 11 ): (7) Use of Formula (7) is frequently more favourable than use of Formula (6) because AA(S 11 ) is sensitive to the charge transfer 9 . R Metaldoes not literally represent the ratio of metallic SWCNTs, because integrated molar extinction coefficients in the M 11and S 11regions (or their relative magnitude) are not completely clarified. In the case of the SWCNT sample with the diameter distribution of 1,1 nm to 1,3 nm, Formula (6) and Formula (7) provid
