Sorry I don't know such kinds of methods to analyze particle of GQs. I don't understand why you are thinking about UV-vis instead of DLS/ELS or TEM/SEM?

However, just one idea knocked in my head. Most probably it does work. First get a standard curve based on excitation wavelength VS particle size of different QDs (blue,green, yellow,red). Then you can take UV spectrum of your unknown QDs. From the standard curve you may a get particle size data (it may not appropriate, i assume).

As you know there is a direct relation between excitation wavelength and particle size of QDs. However, before doing this try to find some reference either exist or not.
Thanks

dear sir
thanks for your valuable suggestion. In some papers, they had calculated the particle size using Brus equation in terms of bandgap of energy (Eg), effective mass of excitons (electron and hole pair). Is effective mass of exciton for all materials same?

Jan 26, 2013

Asiq Rahman · Indian Institute of Technology Patna

Use Brus equation for calculating the particle size...

Joicy, its not a good idea to calculate exact particles size from UV-vis, you can get an idea about size distribution depends on nature of the curve and the position of the peak. if you have narrow peak you have uniform size distribution and if you have broad peak your sample is not uniform or some case different shapes.

Joicy : Sizes of nanoparticles may be determined using the photoluminescence spectra as it presented in our paper. It is possible if you observe structure in the photoluminescence spectra.

Thank you professor Yu. Gnatenko for your suggestions.

Jan 31, 2013

Israel López · Autonomous University of Nuevo León

Hi Joicy, as in your other question, you have two options:

The Brus model (theoretical model based on quantum mechanics, known as the effective mass approximation)
or
An empirical relationship, if it has been previously determined (e.g. Yu model for CdS quantum dots)

Based on the quantum nature of the phenomenon, the simplest relationships between the wavelength corresponding to the absorption edge and the size of the quantum dots are quadratic and cubic functions.

Also, the theoretical model considers only particles with a specific diameter (monodisperse), while an empirical model assumes that the particle diameter is the average diameter of the actually particle size distribution (polydisperse).

[Show abstract][Hide abstract] ABSTRACT: The study of the size evolution of CdS nanoparticles in aqueous dispersion is presented in this paper. The sodium citrate was employed as stabilizer of CdS nanoparticles synthesized by microwave assisted synthesis. Analysis of this study was carried out by UV-Vis spectrophotometry, by comparison of the band gap energy using theoretical and empirical models. Results obtained show that the synthesis conditions produce CdS nanoparticles with diameters below of 6 nm, which remains stabilized by at least 14 days. These characteristics were conﬁrmed by transmission electron microscopy. The X-ray diffraction pattern conﬁrms cubic phase of the CdS nanoparticles.

Full-text · Article · Apr 2013 · Revista Mexicana de Fisica

Particle Size Calculation from UV-Vis.
For metal nanoparticles, size can be calculated from FWHM of SPR peak using equation
FWHM = 50 + 2300 / D.
FWHM (Full Width Half Maximum) and D-particle diameter is in angstroms [Ind. Eng. Chem. Res., 39, (2000), pp. 4749-4755].
For semiconductor nanoparticles, size can be calculated from bandgap. For details refer: Res.Appl.Mat.07/2013; 1(4):36. DOI:10.12966/ram.07.02.2013);

[Show abstract][Hide abstract] ABSTRACT: This work reports aspect related to semi-conducting nature of nano-sized particles of lead. This attempt finds its semiconducting behaviors elaborately and such advanced insight has so far not been said in literatures. New findings of Pb nanopowder (metal) by optical, fluorescence, cyclic voltammetry and four probe studies are presented in this study. UV-Vis analysis confirms the nano nature of the sample i.e. 5 nm and SPR peak confirms its metallic nature. The successful calcula-tions of band gap, temperature dependent resistance value confirm its semi-conducting nature and explore its potential applica-tion in various industries. This work throws some light on and helps further research.

There are different sizing curve equations are given by different researchers to calculate the size of the quantum dot. For instance, this is a paper where you can calculate the size of the Cd(S, Se, Te) quantum dots. It would be nice if you can specify your QDs.

Also, you can say the effective mass for electron and hole for a particular semiconductor as its characteristic property. Though effective masses vary with curvature of band shape.

## All Answers (16)

Md. Nurunnabi· Chungnam National UniversityHowever, just one idea knocked in my head. Most probably it does work. First get a standard curve based on excitation wavelength VS particle size of different QDs (blue,green, yellow,red). Then you can take UV spectrum of your unknown QDs. From the standard curve you may a get particle size data (it may not appropriate, i assume).

As you know there is a direct relation between excitation wavelength and particle size of QDs. However, before doing this try to find some reference either exist or not.

Thanks

Joicy Dora· Pondicherry Universitythanks for your valuable suggestion. In some papers, they had calculated the particle size using Brus equation in terms of bandgap of energy (Eg), effective mass of excitons (electron and hole pair). Is effective mass of exciton for all materials same?

Asiq Rahman· Indian Institute of Technology PatnaAngshuman Pal· Clarkson UniversityJoicy Dora· Pondicherry UniversityYuriy P. Gnatenko· National Academy of Sciences of UkraineYuriy P. Gnatenko· National Academy of Sciences of UkraineSee paper, which attached.

Yuriy P. Gnatenko· National Academy of Sciences of UkraineJoicy Dora· Pondicherry UniversityIsrael López· Autonomous University of Nuevo LeónThe Brus model (theoretical model based on quantum mechanics, known as the effective mass approximation)

or

An empirical relationship, if it has been previously determined (e.g. Yu model for CdS quantum dots)

Based on the quantum nature of the phenomenon, the simplest relationships between the wavelength corresponding to the absorption edge and the size of the quantum dots are quadratic and cubic functions.

Also, the theoretical model considers only particles with a specific diameter (monodisperse), while an empirical model assumes that the particle diameter is the average diameter of the actually particle size distribution (polydisperse).

## Article: Microwave assisted synthesis of CdS nanoparticles and their size evolution

ABSTRACT:The study of the size evolution of CdS nanoparticles in aqueous dispersion is presented in this paper. The sodium citrate was employed as stabilizer of CdS nanoparticles synthesized by microwave assisted synthesis. Analysis of this study was carried out by UV-Vis spectrophotometry, by comparison of the band gap energy using theoretical and empirical models. Results obtained show that the synthesis conditions produce CdS nanoparticles with diameters below of 6 nm, which remains stabilized by at least 14 days. These characteristics were conﬁrmed by transmission electron microscopy. The X-ray diffraction pattern conﬁrms cubic phase of the CdS nanoparticles.Imtiaz Ahmad· Xi'an Jiaotong-Liverpool UniversityDeletedTheivasanthi Thirugnanasambandan· Kalasalingam UniversityFor metal nanoparticles, size can be calculated from FWHM of SPR peak using equation

FWHM = 50 + 2300 / D.

FWHM (Full Width Half Maximum) and D-particle diameter is in angstroms [Ind. Eng. Chem. Res., 39, (2000), pp. 4749-4755].

For semiconductor nanoparticles, size can be calculated from bandgap. For details refer: Res.Appl.Mat.07/2013; 1(4):36. DOI:10.12966/ram.07.02.2013);

## Article: Lead Nanopowder as Advanced Semi-Conductor, An Insight

ABSTRACT:This work reports aspect related to semi-conducting nature of nano-sized particles of lead. This attempt finds its semiconducting behaviors elaborately and such advanced insight has so far not been said in literatures. New findings of Pb nanopowder (metal) by optical, fluorescence, cyclic voltammetry and four probe studies are presented in this study. UV-Vis analysis confirms the nano nature of the sample i.e. 5 nm and SPR peak confirms its metallic nature. The successful calcula-tions of band gap, temperature dependent resistance value confirm its semi-conducting nature and explore its potential applica-tion in various industries. This work throws some light on and helps further research.Ismail Warad· An-Najah National UniversityJayakrishna Khatei· Technion - Israel Institute of TechnologyJayakrishna Khatei· Technion - Israel Institute of TechnologyCan you help by adding an answer?