Introduction to Dynamic Light Scattering Analysis

Dynamic Light Scattering (DLS) is a technique classically used for measuring the size of particles typically in the sub-micron region, dispersed in a liquid. The sensitivity of some modern systems is such that it can also now be used to measure the size of macromolecules in solution.

[@pascalg.5858]

1 hour of class in University failed to explain what you did in 5 Minutes, well done.

[@MalvernPanalytical]

Thank you so much, this is really encouraging. If you need more support, simply contact us.

[@jeetenderkakkar7570]

Pass

[@saiftama]

@@jeetenderkakkar7570 Don't be rude. Thanks Malvern.

[@TheFirebreather]

This video is quite amazingly well done, probably the best one I've seen since I started my masters degree on bioengineering. thank you so much

[@MalvernPanalytical]

That is very kind of you to say, thank you.

[@moonpie3094]

Thank you so much. Perfect overview and just the revision I needed for my exam tomorrow. I find it kind of funny how this short ad explained it far better than my textbook :D

[@MalvernPanalytical]

Glad it was helpful! 😉

[@Dr_Semalti]

finally a perfect video.

[@MalvernPanalytical]

Thanks a lot

[@12345lussy]

Thank you for this video, it was very useful to understand better the DLS. 😊

[@MalvernPanalytical]

You're really welcome. We developed these videos for that purpose.

[@midas7305]

Explained perfectly in under 5 minutes , great video !

[@MalvernPanalytical]

Glad you liked it!

[@Theogtm]

This video helped a lot for my understanding of how DLS works, it will definitely help me my next congress.

[@MalvernPanalytical]

Thanks @Theogtm! Glad the video helped. Good luck with your congress!

[@eliasrichter7262]

Amazing video but frankly i am not able to concentrate on the science if the music slaps THIS hard ;)

[@MalvernPanalytical]

:-)

[@ulfnobbmann6396]

Try it with the sound off, and turn on closed captions CC.

[@tomplayford4794]

cheers mate, this video was actually really helpful. Much better explanation than my Oxford professors lol

[@MalvernPanalytical]

Thank you for your kind words! We’re glad to hear that our video was helpful. We hope you continue to find our content informative and engaging. 😊

[@a199719971997]

Studying for a phd. This video did wonders, thank you

[@MalvernPanalytical]

Glad it was helpful!

[@bhavishapatel8510]

Was looking for such a descriptive video from a very long time

[@MalvernPanalytical]

Glad you liked it

[@santircastillo]

Amazing explanation, very clear and straightforward. Thanks a lot!

[@MalvernPanalytical]

Glad you enjoyed it!

[@estefaniaperri2655]

Is it Kurzgesagt's cousin or what?. Amazing...Thank god these people exist.

[@sathvikbhat3529]

The autocorrelation is well explained, it was tough to understand before. Thanks.

[@MalvernPanalytical]

Thank you very much Sathvik

[@prajwalp1483]

Amazing video, very well explained. Thank you

[@MalvernPanalytical]

You're very welcome!

[@karahood9706]

BEST explanation of DLS, definition of autocorrelation, and how hydrodynamic radius is calculated.

[@MalvernPanalytical]

Thanks for your comment! We’re glad you found our video helpful. Let us know if you have any other questions or comments.

[@MN-mj9ok]

Thank you. Please make a video about nano particle tracking analysis (NTA)

[@jessicawu2084]

Hi there, I find this video is super helpful for me to understand DLS, however, I wonder under which author name (s) I should cite this source? Thank you!

[@MalvernPanalytical]

Thanks for your question and for sharing our video. Just cite Malvern Panalytical and include our website or KZbin channel.

[@srishtisahu965]

Such a nice explanation...Just what needed! Thank you for this amazing video.

[@MalvernPanalytical]

You're very welcome Srishti.

[@noemizsofiacsik5840]

Thank you very much! This video is a big help to understand this technique!

[@MalvernPanalytical]

Happy to see that our video is useful to you, thanks for your feedback.

[@lantianlu9959]

I had been looking for a video like this

[@MalvernPanalytical]

Thanks a lot, nice to see that our videos are appreciated.

[@gokulk715]

Nice and straightforward explanation. Thanks :)

[@MalvernPanalytical]

Glad it was helpful!

[@s1mple-csgo]

This video is being shown in our classroom. Thanks for the video

[@MalvernPanalytical]

That's awesome!

[@nevzatalperdinc]

Great video! How does the instrument calculate the translational diffusion coefficient?

[@MalvernPanalytical]

Thanks for your comments and we are pleased you liked the video. The diffusion coefficient is obtained from the relation Γ=D t q 2 where q is the scattering vector, given by q=(4πn/λ0)sin(θ/2). A fuller explanation can be found here - www.malvernpanalytical.com/en/learn/knowledge-center/technical-notes/tn101104dynamiclightscatteringintroduction

[@arammamo4434]

Thanks for video very useful. which particle size is better smaller or large and why ?

[@MalvernPanalytical]

Thanks for the question - there is no short answer to that question and it really depends on what the application the particles are being used for and the purpose of measuring them. In some cases, such as for biologic applications, you may already know what particle size to expect and the purpose of measurement is to see if results match your expectations - if they don’t then maybe the sample has agglomerated or changed in some other way. At other times you may want to design a system to have an explicit particle size as theory says it will perform at an optimum for that application - such as reactivity or release profile or availability. At other times you may want your particles to interact, agglomerate or assemble - so presence of monomeric state particles could be bad for the application. Sorry, it’s not an explicit answer - but you need to consider the use of the particles to determine which is “better”.

[@josueliriano]

Very informative with beautiful graphics.

[@MalvernPanalytical]

Glad you liked it

[@amyknodel143]

this video is amazing super comprehensive, thank u :-)

[@MalvernPanalytical]

You're welcome. Happy to hear that you appreciate this new video

[@nidaiqbal2671]

Thank you . video was very informative. I have a question, Is REfractive index of material important for analysis???

[@MalvernPanalytical]

Hi Nida, The refractive index of the material is only important in DLS measurements if you want to convert the intensity size distributions to volume or number distributions. Hope this helps.

[@nidaiqbal2671]

@@MalvernPanalytical thanks yes it is helpful.

[@hellomeloO]

Thank you. Watching this before my committee meeting :)

[@MalvernPanalytical]

Hope your meeting went well.

[@GlossKarin]

Great video! But why in the Stokes-Einstein equation there is 3 in the denominator, and not 6? Cheers

[@GlossKarin]

@gudipati srinivasarao Makes sense! Thank you!

[@MalvernPanalytical]

Thanks for the feedback, it’s a 3 as the formulae is expressed as a diameter and not in radius terms, that you maybe more familiar with.

[@vickykachari5350]

Thank you for the explanation... I m studying nanomaterials now.. Have exam tomorrow

[@MalvernPanalytical]

Hope your exam went well.

[@malakdia6839]

Thank you for the video , it is very usefull ! but i have a question please : how can i know the difference between the hydrodynamic diameter and the real diameter of a Nanoparticle ?

[@MalvernPanalytical]

Thanks for your question Malak. Firstly, I assume you mean the core diameter or hard sphere diameter by real? Both hydrodynamic and core diameters are “real” and which you use depends of course on how you measure them and how you want to use them. What is the important physical parameter in your application? The hydrodynamic diameter accounts for any electric double layer that moves with your particles, if anything is absorbed or bonded to the surface of the particles or if your particles are “soft”. Measuring your samples at high electrolyte concentrations, where the electric double layer is most compressed, will get you closer to the core diameter. For instance we will typically measure standard polystyrene spheres in 10mM NaCl solution to reduce the double-layer. However, this might not always be possible as it could disrupt the chemistry of your sample. If you know the electrolyte composition of your continuous phase then it may be possible to estimate the double-layer thickness using Gouy-Chapman-Stern model for instance. The other, and perhaps easier way, is to measure the particle size by a technique such as SEM or TEM which will typically measure the core size. Hope that helps but difficult to give more specific advice without knowing your application. If you need more help then please contact your MP representative

[@sabyasachibiswal7092]

Very nice information

[@ananyaverma6858]

Amazing video. Is there a similar video for SLS and ELS? If someone knows, please help.

[@ulfnobbmann6396]

Thanks for the compliment! So far, this is the first light scattering video in this channel, no ELS or SLS. However, I will share your request with the team.

[@ananyaverma6858]

@@ulfnobbmann6396 thanks a lot!

[@purushottamdubey2618]

The snapshot shown suggest that whole I vs t graph is generated at each instant of time Snapshot!, the whole I vs t->tn graph is measured at each time t-t>n and generates intensity snapshots of I vs t in complete t->tn range! Does it mean autocorrelation function is calculated using intensity measured in complete t OR it measures Intensity fluctuation from t->tn from this autocorrelation calculated from intensity measured at t=0 and t=t+tn, and not the snapshot in whole time range generated from t = 0 to t = tn

[@MalvernPanalytical]

Thanks for the question. I am not 100% clear I fully understand the terminology you have used. But to try and clarify - we measure the autocorrelation function of the intensity. This is always compared to t0 as the initial point of reference. Subsequent measurements of the intensity are taken at short time intervals from t0 and correlated with the intensity at t0. Obviously we can’t generate the intensity vs time at just one instance. We think the animation clearly shows the autocorrelation function being derived sequentially over several time intervals from t0. Hope this clarifies what is happening in this regard.

[@brhaneamha]

Bravo , what a masterpeice work ! Thanks!

[@MalvernPanalytical]

Many thanks, Brhane.

[@tapaspal3921]

how the autocorrelation function being fitted by non negative least square method or cumulant analysis method ? please respond

[@MalvernPanalytical]

Hi Tapas Pal, size is obtained from the correlation function by using various algorithms. There are two approaches that can be taken (1) cumulants determines the mean size (z-average diameter) and an estimate of the width of the distribution (polydispersity index) and is defined in ISO22412 (2018)) (2) a multiple exponential fit of the correlation function to obtain the distribution of particle sizes. There are various distribution algorithms available such as non-negative least squares (General Purpose or Multiple Narrow Modes or L-Curve). www.malvernpanalytical.com/en/learn/knowledge-center/faqs/FAQ160705CumulantsNNLS Hope this helps.

[@bijayaghosh5158]

Excellent video

[@MalvernPanalytical]

That's really kind of you, we try to develop the best video for you,

[@inskmansuri2973]

Superb explanation

[@MalvernPanalytical]

Thank you 🙂

[@jexy2525]

How does the machine "know" when there are multiple sizes of particles in the sample when there is only one graph of intensity over time? How does the analysis give out multiple translational diffusion coefficients (D)?

[@MalvernPanalytical]

Thanks for the question. DLS in its simplest form uses Cumulants analysis of the auto-correlation function and that analysis will only provide a mean particle size (the Z-Average size) and a measure of the width of the size distribution (the polydispersity). To extract particle size distribution data a secondary analysis is required and several models for this are available and often proprietary to a manufacturer - these include Non-Negative Least Squares or CONTIN analysis for instance.

[@nandaacademy]

Great video!

[@MalvernPanalytical]

Glad you enjoyed it

[@王璐-l1b]

A really good video. cool!

[@MalvernPanalytical]

Thank you so much.

[@c_nazifahumairabintiabdulr2014]

u saved my life

[@MalvernPanalytical]

You're welcome

[@نوريوسف-س2ج]

thank you >> very helpfull illustration

[@MalvernPanalytical]

Thanks for sharing your feedback. Enjoy!

[@jexy2525]

Does the diffusion rate not take into account the density of the particles of the sample? If you have 2 particles of the same size, but one is much more lighter, the lightest one will be more affected by collisions of the solvent, hence, diffuse faster. Is this correct? Does DLS assume a certain density?

[@MalvernPanalytical]

Thanks for good question Jesky. We use (as all DLS systems do) Stokes-Einstein (S-E) equation to derive particle size from the diffusion coefficient. In S-E the factors affecting the diffusion coefficient are temperature, kinematic viscosity (also temperature related) and particle diameter. Particle density would mainly affect the inertia of a particle and this is a negligible quantity in the sample states typically studied by DLS. Particle density will come into play in terms of defining the upper size limit of DLS. Typically for DLS measurements particles should be freely diffusing. When particles have sufficient mass they will exhibit a gravitational component to their movement and can no longer be thought of as freely diffusing. There will still be a translational diffusion component but with increasing mass (density or size increase) this will become a smaller fraction compared to its gravitational component. So, the upper size limit by DLS for polystyrene beads will be greater than that of a gold sphere for instance. Hope that helps.

[@jexy2525]

@@MalvernPanalytical I understand. Thank you for both answers. Great video by the way! :)

[@MalvernPanalytical]

Happy we could help, thank you for the compliment.

[@ericktoledofranco9147]

Im sorry, but i still don't understand why sometime in Stoke-Einstein Equation are putting 3 as a constant and sometime 6 Someone could explain?, please!

[@deowere]

Hi Erick, the difference will be if you're calculating the hydrodynamic radius or diameter. Hope this clarifies it, but feel free to contact Malvern helpdesk if you have further questions.

[@ericktoledofranco9147]

@@deowere Thank yout Diogo

[@kamalis6058]

Very efficient.. Understood

[@MalvernPanalytical]

Thanks a lot

[@iluan_]

I have a question. Could this technique be applied for a dispersion that is not static?

[@MalvernPanalytical]

Hi Iluan, thanks for the question. I am not 100% clear what you mean - we rely on the dispersion being free to move/diffuse so that the scattering intensity varies over time. DLS would not work if the particles were static (frozen). But perhaps you meant something else, if so perhaps you can clarify your question?

[@iluan_]

@@MalvernPanalytical Hello. What I mean is for a sample where the media itself is moving. For instance, a solution that is flowing through a pipe or that is being stirred inside a reactor. I worry that the macro-level movement of the liquid would interfere with the analysis of the movement of the particles.

[@MalvernPanalytical]

Hi Iluan, thank you for elaborating. DLS can work in a flowing system, but the flow generally needs to be low (

[@sugarnoname8405]

thanks for this informative video

[@MalvernPanalytical]

Glad it was helpful!

[@Muhammad-h2p6f]

How do we measure carbon nanotubes particle size in suspension using Master sizer

[@MalvernPanalytical]

Hi, do you mean Mastersizer? Mastersizer uses Laser Diffraction and the video you posted on is around Zetasizer, this uses Dynamic Light Scattering. Both techniques maybe useful in measuring CNT’s - dependent on their size range and agglomeration state. If you can clarify what system you have we can point you in the right direction.

[@Muhammad-h2p6f]

@@MalvernPanalytical Hi, we have Master sizer with EV and MV unit. CNT size is 9.5nm. I have a CNT water dispersion 200ml. Please advise what shall me sample volume and which technique I must use. Many thanks

[@MalvernPanalytical]

@@Muhammad-h2p6f Your expected size of 9.5 nm is below the 10 nm lower limit of the Mastersizer (laser diffraction), but this is well within the capabilities of the Zetasizer (dynamic light scattering). However, aggregation of the CNTs will likely mean you measure sizes larger than 9.5 nm and so the Mastersizer should still be relevant. We cannot advise on volume of sample to be tested as we do not know the concentration etc. Best practice for Mastersizer dictates that you should aim for an obscuration of no more than 5%. As these are small particles, there is a high likelihood of multiple scattering at higher obscuration levels. Try measuring at different obscuration ranges and determine where you see stable sizes versus obscuration - it’s within this range that you should be testing.

[@Muhammad-h2p6f]

@@MalvernPanalytical Many thanks for the reply. The concentration is 1%. please advise the volume of sample.

[@MalvernPanalytical]

Hi @user-vf3mp5nn8l I would suggest to contact your local support for more advice.

[@elormoboteyezugbe3159]

Great content👍

[@MalvernPanalytical]

Thank you 🙌

[@fatemerezaee4369]

Thank to this video, finally I figure it out :)

[@MalvernPanalytical]

You are welcome!

[@Lina-ob9ug]

can u do a video about SLS too plz

[@MalvernPanalytical]

Thank you Lina, we will take that into account.

[@S3IIL3CT]

really good video but what is that music xD

[@MalvernPanalytical]

Thank you for watching! The music was chosen to match the video's tone. We're sorry if it wasn't to your liking, but we hope it didn't affect your enjoyment. We're open to suggestions for future videos. Thanks again!

[@S3IIL3CT]

@@MalvernPanalytical It was a great informative video. The main issue was the music being a bit loud, so focussing on the voice explaining was a little difficult for me.

[@HZAexNB]

I'm sorry, i still dont understand whats the meaning of the snapshot, could someone explain it?, Btw great video tho

[@jadelight1984]

it means a photograph of the screen or the result in this case, just like the snapshots taken in mobile

[@HZAexNB]

Thanks, but why did it give different result when we make the auto correlation graph?

[@MalvernPanalytical]

By snapshot we mean a measure of the data at any point in time, typically for correlation this is time zero compared to some other positive increment of time from time zero. It allows us to statistically compare the temporal relationship of the data. I hope that makes sense?

[@hasanlamat2329]

the background music is so distracting

[@ulfnobbmann6396]

You can mute the sound on the video and turn on closed captions CC. The autogenerated captions are pretty close.

[@niesnerful]

Well, and now lets find out how to cite a yt video to my final thesis :D :D

[@MalvernPanalytical]

Thanks for your comment! We're thrilled you enjoyed the video! 😄 For citing KZbin videos in your final thesis, consider following the guidelines provided by your academic institution or referencing style (like APA, MLA). Best of luck with your thesis! 📚✨

[@vinodhinijanakiraman5627]

Can u give the ppt of this vedio

[@MalvernPanalytical]

Thanks for the enquiry but there is no PowerPoint for the video, welcome to use as long as Malvern Panalytical is credited appropriately.

[@vinodhinijanakiraman5627]

@@MalvernPanalytical thanks for ur reply it was a very gud presentation

[@RebeccaToft-o7z]

The background music is insanely distracting imo. Destroys an otherwise very well done introduction.

[@MalvernPanalytical]

Thank you for your feedback! We appreciate your honesty and understand that the background music may not be to everyone's taste. We'll take your comment into consideration for future videos and do our best to strike a better balance between the music and the narration so that it enhances rather than detracts from the viewing experience.

[@Shayoyo2013]

Informative video but get rid of the loud background music.

[@MalvernPanalytical]

Hi @Shayoyo2013, thanks for your feedback! We’re glad you found the video informative. We’ll definitely take your suggestion about the background music into consideration for future videos. 😊

[@jeetenderkakkar7570]

Light passbook

[@etedali1975]

Really not able to watch the video because of the loud disturbing music. It should be a informative clip not party. Really not helpful broke it up after one minute torturing to understand anything.

[@MalvernPanalytical]

Sorry you didn’t like our choice of background music

[@ulfnobbmann6396]

You can mute the sound and turn CC = closed captions on. Then the distracting music is gone, as well as the voice. The autogenerated captions are pretty close.