BS PD ISO TS 17466-2015 Use of UV-Vis absorption spectroscopy in the characterization of cadmium chalcogenide colloidal quantum dots《在镉硫胶体量子点表征中使用紫外-可见吸收光谱法》.pdf

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1、BSI Standards Publication PD ISO/TS 17466:2015 Use of UV-Vis absorption spectroscopy in the characterization of cadmium chalcogenide colloidal quantum dotsPD ISO/TS 17466:2015 PUBLISHED DOCUMENT National foreword This Published Document is the UK implementation of ISO/TS 17466:2015. The UK participa

2、tion in its preparation was entrusted to Technical Committee NTI/1, Nanotechnologies. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for

3、its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 82527 9 ICS 07.030 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of the Standards Poli

4、cy and Strategy Committee on 31 August 2015. Amendments issued since publication Date Text affectedPD ISO/TS 17466:2015 ISO 2015 Use of UV-Vis absorption spectroscopy in the characterization of cadmium chalcogenide colloidal quantum dots Utilisation de la spectroscopie dabsorption dans lUV-visible p

5、our la caractrisation des points quantiques collodaux des chalcognures de cadmium TECHNICAL SPECIFICATION ISO/TS 17466 Reference number ISO/TS 17466:2015(E) First edition 2015-08-01PD ISO/TS 17466:2015ISO/TS 17466:2015(E)ii ISO 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2015, Publishe

6、d in Switzerland All rights reserved. Unless otherwise specified, 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

7、 can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright 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.orgPD ISO/TS 17466:2015ISO/TS 17466:201

8、5(E)Foreword iv Introduction v 1 Scope . 1 2 T erms, definitions, and abbr e viat ed t erms . 1 2.1 Terms and definitions . 1 2.2 Abbreviated terms . 1 3 Principle 2 3.1 General . 2 3.2 UV-Vis absorption spectroscopy 2 3.3 Absorption peaks of quantum dots in the UV-Vis region 2 3.4 Relation between

9、quantum dot diameter and optical absorption peak wavelength . 3 3.5 Relation between quantum dot concentration and optical absorption peak intensities . 4 3.5.1 Normalization of absorbance A for samples with wide size distributions 4 3.5.2 Derivation of extinction coefficient from particle size 4 4

10、Sample preparation . 5 5 Measurement procedure 5 5.1 UV-Vis spectrometer . 5 5.2 Optical measurement procedure . 5 5.3 Recommended conditions . 5 6 Data analysis and interpretation of results 5 6.1 Data analysis for approximation of QD size . 6 6.2 Data analysis for characterization of QD concentrat

11、ion 6 7 Measurement uncertainty 6 8 Test report . 6 Annex A (informative) Case study for determining the diameters of CdSe QDs from UV-Vis absorption spectra . 8 Annex B (informative) Case study for determining the number concentrations of CdSe QDs in a dispersion 15 Bibliography .18 ISO 2015 All ri

12、ghts reserved iii Contents PagePD ISO/TS 17466:2015ISO/TS 17466:2015(E) 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 tech

13、nical 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

14、 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 nee

15、ded 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

16、 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 i

17、n this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barri

18、ers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this is document is ISO/TC 229, Nanotechnologies.iv ISO 2015 All rights reservedPD ISO/TS 17466:2015ISO/TS 17466:2015(E) Introduction Engineered nanoparticles of semiconductor materials with

19、sizes down to the extent where the behaviour of electrons and holes are affected by the quantum confinement often possess unique electronic and optical properties intermediate between those of bulk semiconductors and those of discrete molecules. This normally refers to a nanoparticle diameter compar

20、able to the Bohr radius of the exciton for the particular semiconductor material. Such nanoparticles are generally called quantum dots (QDs). A significant feature of these nanoparticles resulting from quantum confinement of charge carriers is size dependence of their electronic structure and, conse

21、quently, the excitonic absorption and emission wavelengths. Particularly, the transition energy from the valence band to the conduction band, and consequently the onset of absorption and the first excitonic transition (referred to here as first absorption peak position), is a function of the diamete

22、r of the particle (see Reference 1). Quantum dots commonly present sophisticated core-shell structures with a ligand shell controlling solubility and subsequent chemical functionalization. They are typically synthesized by chemical methods, with large-scale production and their size, shape, composit

23、ion, and structure control capabilities. Commercially available quantum dots are mainly made from cadmium chalcogenide (CdTe, CdSe, CdS) materials. The size dependence of emission maximum, narrow emission band width, and good photostability make these engineered nanoparticles appealing in biological

24、 labelling and opto- electronics applications (see Reference 2). Ultraviolet-visible (UV-Vis) absorption spectroscopy has become a routine method to characterize QDs in a colloidal dispersion, by utilizing the relationship between the wavelength of the first excitonic absorption peak and the particl

25、e size that has been established after extensive photophysics research in the past, and using analytical methods for high-quality cadmium chalcogenide (CdTe, CdSe, CdS) materials of narrow size distribution. Key properties, such as average nanoparticle size and number concentration, can be approxima

26、tely calculated from the measured absorption spectra. This Technical Specification intends to facilitate the use of UV-Vis spectroscopy for the characterization of quantum dot colloidal dispersions. ISO 2015 All rights reserved vPD ISO/TS 17466:2015PD ISO/TS 17466:2015Use of UV-Vis absorption spectr

27、oscopy in the characterization of cadmium chalcogenide colloidal quantum dots 1 Scope This Technical Specification provides guidelines for estimating the diameter and the number concentration of monodisperse cadmium chalcogenide (CdTe, CdSe, CdS) quantum dots (QDs) with a narrow size distribution in

28、 a colloidal dispersion using Ultraviolet-visible (UV-Vis) absorption spectroscopy. The analysis of the spheroidal particle size is applicable to the diameter range of 3,5 nm to 9 nm for CdTe, 1 nm to 8 nm for CdSe, and 1 nm to 5,5 nm for CdS and is recommended for samples with narrow size distribut

29、ions. 2 T erms, d efinitions , and abbr e viat ed t erms 2.1 T erms and definiti ons For the purposes of this document, the following terms and definitions apply. 2.1.1 quantum dot QD crystalline nanoparticle that exhibits size-dependent properties due to quantum confinement effects on the electroni

30、c states SOURCE: ISO/TS 27687:2008, definition 4.7 2.1.2 qu a nt u m c on f i ne me nt boundary condition resulting in phenomena when electrons and holes in a material are confined by a potential well in one dimension (quantum well), in two dimensions (quantum wire), or in three dimensions (quantum

31、dot) SOURCE: ISO/IEC DTS 80004-12, definition 2.5 2.1.3 f i r s t e xc i t on ic a b s or p t ion light absorption in quantum dots originating from the electronic transition from ground state to first excitonic excited state 2.2 Abbreviated terms QD quantum dot TEM transmission electron microscopy T

32、OPO trioctylphosphine oxide OPA n-octylphosphonate HDA hexadecylamine TECHNICAL SPECIFICATION ISO/TS 17466:2015(E) ISO 2015 All rights reserved 1PD ISO/TS 17466:2015ISO/TS 17466:2015(E) HWHM half width at half maximum FWHM full width at half maximum PPA P-P-(di-n-octyl) pyrophosphonate UV-Vis ultrav

33、iolet-visible E 1s energy of first excitonic transition I intensity of light transmitted through a sample I 0 intensity of incident light before it passes through the sample A absorbance d particle diameter wavelength molar extinction coefficient c particle number concentration l path length 3 Princ

34、iple 3.1 General The absorption spectrum (absorbance A as a function of wavelength) of a QD colloidal sample with a narrow size distribution shows discrete peaks, due to the quantized energy levels in the quantum dots. Among these, the first excitonic absorption contains information on particle size

35、 (through the wavelength of the peak maximum), size distribution (through the peak HWHM), and concentration (through the peak intensity). 3.2 UV-Vis absorption spectroscopy The intensity of light passing through a sample (I) is measured and compared to the intensity of incident light (I 0 ). The abs

36、orbance, A, is expressed as log (I/I 0 ). The plot of the absorbance against wavelength for a particular compound is referred to as an absorption spectrum. 34 3.3 Absorption peaks of quantum dots in the UV-Vis region A typical optical absorption spectrum of colloidal CdSe QDs is shown in Figure 1. T

37、he lowest energy (longest wavelength) first excitonic absorption peak at 545 nm is attributed to the excitonic transition from the valence band to the conduction band.2 ISO 2015 All rights reservedPD ISO/TS 17466:2015ISO/TS 17466:2015(E) Key 1 first excitonic absorption peak X wavelength/nm Y absorb

38、ance Figure 1 Typical optical absorption spectrum of CdSe quantum dots in a dispersion 3.4 Relation between quantum dot diameter and optical absorption peak wavelength Chalcogenide specific relationships have been established between the nanoparticle number averaged Feret diameter, d, (in nm) determ

39、ined mainly by TEM and the wavelength, , (in nm) of the lowest energy excitonic absorption peak in the UV-Vis absorption spectra. The relationship formulae are recommended as follows (see Reference 5): For CdTe: d = A + B + C 2+ D 3(1) coefficient A B C D value with unit 194,84 nm 10 064 1,714 7 10

40、3nm 1 9,812 7 10 7nm 2 For CdSe: d = A + B + C 2+ D 3+ E 4(2) coefficient A B C D E value with unit 41,57 nm 0,427 7 1,624 2 10 3nm 1 2,657 5 10 6nm 2 1,612 2 10 9nm 3 For CdS: d = A + B + C 2+ D 3(3) coefficient A B C D value with unit 13,29 nm 9,235 2 10 2 1,955 7 10 4nm 1 6,652 1 10 8nm 2 ISO 201

41、5 All rights reserved 3PD ISO/TS 17466:2015ISO/TS 17466:2015(E) These formulae allow the users to approximate the average size of monodisperse QD from a measured absorption spectrum. The analysis is applicable to the size range of 3,5 nm to 9 nm for CdTe, 1 nm-8 nm for CdSe, and 1 nm to 5,5 nm for C

42、dS. Given the approximative nature of the formulae above, and the various approximations made both in the TEM measurements and the UV-Vis measurements, the d-values determined shall be reported as: UV-Vis absorption peak equivalent QD diameter (obtained according to ISO/TS 17466). 3.5 Relation betwe

43、en quantum dot concentration and optical absorption peak intensities According to the Beer-Lambert law Formula (4), the molar extinction coefficient (in the unit of L mol 1 cm 1 ) is related to A at the first excitonic absorption peak position, with particle concentration c in mol L 1and path length

44、 l in cm. A = c l (4) The concentration c of QDs can be calculated if A, I, and are known. Given the approximative nature of Formula (4), and the various approximations made in the UV-Vis measurements, the c-values determined shall be reported as: UV-Vis absorption peak equivalent QD concentration (

45、obtained according to ISO/TS 17466). 3.5.1 Normalization of absorbance A for samples with wide size distributions For the purpose of this Technical Specification, QDs with a size standard deviation less than 10 % are considered monodisperse. For samples with broader size distributions, it is necessa

46、ry to take into consideration the resulting absorbance peak broadening and normalize the value of the absorbance A at the first excitonic absorption according to the following formula. A = A m(HWHM) m /(HWHM) ref(5) where A mis the measured absorbance, (HWHM) mis the measured half width at the half

47、maximum (HWHM) on the low energy side of the first exciton absorption peak and (HWHM) refis a reference value obtained for a corresponding high quality colloidal II/VI quantum dot, 18 nm, 14, and 11 nm for CdTe, CdSe, and CdS, respectively. 5 3.5.2 Deri v ation of e xtinction c oefficient fr om p ar

48、ticle size When the first excitonic absorption energy or the diameter of the QDs is known, can be calculated from the following formulae, as recommended in References 5 and 6: For CdTe: = 10 043 (d) 2,12(6) For CdSe: = 155 507 + 6,670 54 10 13 exp(-E 1s /0,105 51) (7) For CdS: = 21 536 (d) 2,3(8) wh

49、ere d is a particle diameter (in nm), and E 1sis the energy of the first excitonic transition (in eV). Formulae (6) and (8) are taken from Reference 5 and Formula (7) is taken from Reference 6. Conversion between the wavelength in nm and transition energy E in eV is through (nm) = 1240/E (eV ).4 ISO 2015 All rights reservedPD ISO/TS 17466:2015ISO/TS 17466:2015(E) 4 Sample preparation For the measurement of absorption spectra, a ho