Secret of Dynamic Light Scattering (DLS) for particle size analysis

Dynamic Light Scattering (DLS) is a mature and advanced technique in characterizing size and size distribution of particles dispersed in suspension, specifically in the nanometer and sub-micron range.
A warm welcome to the Bettersize Lab! Watch Bettersize's application engineer Shelly Zhang gives an introduction to Dynamic Light Scattering (DLS) for particle size analysis with the magnitude of 1-nanometer to10-micrometers.
The scattered light intensity depends on the particle's intrinsic physical properties such as size and molecular weight. The scattered light intensity is not a constant value; it fluctuates over time due to the random walk of particles that are undergoing Brownian motion. The fluctuations in scattered light intensity with time allow us to calculate the diffusion coefficient through the autocorrelation function analysis. Then using the Stokes-Einstein equation, the particle size distribution can be calculated from the diffusion coefficient. This technique is called dynamic light scattering, abbreviated as DLS.
For more information on DLS technology, please visit: www.bettersizeinstruments.com...
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0:00 - Start
0:37 - Theory of DLS​
6:20 - Optical Setup
17:30​ - Sample preparation
24:02 - Result interpretation
27:19 Summary

[@willlucas2491]

Very good presentation and great information, thank you.

[@BettersizeInstruments]

Glad that you found it helpful!

[@muhammadasrar05]

Very informative and to the point explanation.

[@BettersizeInstruments]

Glad that you found it helpful!

[@alimohammadhosein7348]

Complete and so helpful.

[@BettersizeInstruments]

Thank you! We are glad that you found it helpful.

[@nidaiqbal2671]

Thanks for your respond...

[@BettersizeInstruments]

We keep the honor to help you. Hope your issue is solved

[@nidaiqbal2671]

Yes issue iz resolved thanks

[@tythanh2496]

PDI is used as variance of DLS analysis, but sometimes it's may be over 1 or reach 1000😱. Can you help me this case?? I'm a student, thank you so much.

[@BettersizeInstruments]

There are many reasons causing high PDI. Commonly, the sample is not dispersed well, the sample is a highly polydispersed one that is not suitable for DLS analysis, the malfunction of the instrument, etc. Since you did not detailedly explain the statement of characterization, it's difficult for us to find out the actual reason. You can send the details of measurement to us at [e-mail] or visit our website for more information: www.bettersizeinstruments.com

[@nidaiqbal2671]

Refractive index is of material or solvent required for the analysis?

[@BettersizeInstruments]

The refractive index of the medium, or the solvent in which sample particles are dissolved, is required for the size measurement of nanoparticles using DLS. This is because the scattering vector calculation requires the refractive index of the medium (as shown in the first equation on the slide about the correlator). However, the refractive index and viscosity of the sample are not required. I hope this clears things up a little! if you have more questions feel free to contact us at [e-mail]

[@nidaiqbal2671]

Your presentation is very helpful but i have query about the refrective index. What is the use of refractive index for size and zeta potential measurements of nanoparticles? And is it necessary parameter for analysis?

[@BettersizeInstruments]

Hi Nida, thank you for your question! The refractive index is used to calculate the scattering vector and yes, it is a necessary parameter for analysis. The same is valid for zeta potential measurement of nanoparticles using the electrophoretic light scattering (ELS) technique.

[@nidaiqbal2671]

Thanks for your reply...i have a confusion about which RI we should consider most important dispersant or material???

[@BettersizeInstruments]

@@nidaiqbal2671 Only the dispersant RI is involved in the particle size calculation in DLS

[@nidaiqbal2671]

Thanks but i am using zetasizer software. The software is asking about RI of material.should i ignore it?

[@BettersizeInstruments]

@@nidaiqbal2671 Since zetasizer software and Bettersize BeNano software (for BeNano 90 Zeta: nanoparticle size and zeta potential analyzer) share no similarities, it's better to ask zetasizer software provider.