Hi,

DLS-Systems are available from Malvern or Horiba. They cost ~ 30000 - 40000 $. I used to work on a Zetasizer nano. It was quite a nice machine... Check it out: http://www.malvern.com/en/products/product-range/zetasizer-range/zetasizer-nano-range/zetasizer-nano-zs/

Best regards.

A number in that ball park is plausible, but what laser do you get with it?

What are you planning to do experimentally?

Issues: Shortest delay time.  Largest delay time.  Maximum acceptable count rate of detector.  Can you actually access the true correlation function \ sum_i  n_i n_{i+j} or is buried in normalizations and roundoffs before you reach it?

Ease of alignment?  Number of channels? Ease of changing scattering angle? Laser source choice? (for weakly scattering samples, you may really want a large Ar laser, say 4W).

Will it take square as well as round scattering cells?  This may be much more than you wanted to know.

Also, do you have someone familiar with the technique who is accessible?  Except for dilute samples in simple solvents, QELSS out of a box is a technique with hazards for naive users.

I am also planning to do similar work and recently I found TA instrument has an attachment small angle light scattering what can be fitted with my Discovery HR3 rheometer> However the price is about US$25-30K. Let's see.

I fully agree with the following statement of George: "Except for dilute samples in simple solvents, QELSS out of a box is a technique with hazards for naive users."

A "decent" research instrument alowing the experimentator to have a good control over the experiment and even more importantly data evaluation costs  form 100-150 kEUR. Such an instrument is certainly not a "black-box" instrument. Most importantly, proper handling of such an instrument calls for a skilful operator. Similarly, avoiding missinterpretation of the DLS results calls for at least good basic knowledge on the DLS theory.

As you can see from the previous answers, the answer to your question depends on exactly what you want. Since you are in a Physics department, you might like to build your own, using a stand alone correlator, from the excellent ALV, for instance. As usual, this approach gives more work, but also total control of equipment specification, measurements and data analysis. This route is probably not cheaper, given the economies of scale that companies like Malvern Instruments have. Frank Scheffold's group in Fribourg, Switzerland is a good example of the build-your-own approach.

The DLS technique is very usefull to determine the conformation of marcomolecule : the hydrodynamic radius and the intercation intermacromolecular...The technique is limited on the dilute regime concentration

What parts do you need?

Space: You need an area that is made light-tight.  Boxes on top of tables give you extreme difficulties with alignment, because the struts are perpetually in the way.

Laser. For a starter system a helkium-neon laser used to be good, but issues havce changed.  A 4W Argon-ion laser is good.  Diode lasers, for example frequency-doubled, in my experience can give very good noise figures, but in my experience are unreliable.

Table: A vibration-isolation table, something like 5x10' with spaced holes in the top.

Optical train: Focusing lens before the scattering cell, collecting optics afterwards.  I recommend pinholes as the collecting optics.  You usefully want to be able to drop a mirror into place after the pinholes, so after carefully checking scattered intensity you can see what is in the cell.

A rotating arm/goniometer that lets you do detection at different angles can be very important.

Detector, followed by something that will give you TTL (other choices exist) pulses afterward.  You really want something that will handle several times 10^5  or more pulses a second safely.  The smaller the photosensitive area, the more painful alignment will be.

Temperature controller...to get stability, you need a refrigerated bath; heating only is unsatisfactory.

Digital correlator:  A many-channel multitau correlator, something that does not lose photocounts when the channel width increases.

Computer.

Ancillary optics: An interference filter at your laser wavelength, to reduce fluorescence noise, is sometimes useful.

You also need a preparatory laboratory to clean your scattering cells, prepare samples, etc.

100-150,000 Euros sounds expensive; a usual selling point of QELSS is that the system is relatively cheap to set up..  However, you may be charged for air conditioning (not an option), power and water supplies for the argon-ion laser if any, etc.

George, a good commercially available research DLS instruments (e.g. from LS Instruments or ALV) were in this range the last time that I checked. Of course it is best to check such info directly at the producer of the instrument, who will be certainly interested to provide also all the detailed specification of the instrument and usually even the comparison with the instrument from their competition. For example, we have set up 3D-DLS instrument from LS Instruments in our lab back in 2007 and the total costs were closer to 150 kEUR already at that time (no air conditioning included, but it is true that we also bought dn/dc instrument for this lab that is useful in combination with SLS measurements that are also possible on this instrument...). Of course if one would build such an instrument by himself the price could be much lower, but for this a decent level of "know-how" is required - I most certainly would not suggest this approach to someone who just had the first contact with this field. Similarly, of course there are much cheaper DLS instruments also available commercially on the marked, but I am afraid that those are more like "black-box" instruments - I think that such instruments are good for let's say some quality control in an industrial lab (they more or less deals with very similar samples all the time and the biggest issue is the comparison of the DLS results with those of some reference sample), but I would not recommend them for a research lab. This is of course only my opinion.

By the way, the most important point in deciding for the 3D-DLS Spectrometer in our case was its ability to eliminate problems with the multiple scattering - this problem is solved by the sole nature of the 3D-DLS cross-correlation approach. However, if somebody would only deal with transparent (non-turbid) samples this would of course not be needed. Unfortunately, a lot of interesting samples are at least slightly turbid...

Regarding the laser power… I think that 35 mW laser is more than enough for DLS instrument and that one should not significantly exceed this power during the DLS experiment even if the instrument is equipped with the high power laser. Therefore I would hesitate to recommend a high-power laser like 4 W lasers for usual use in DLS. With DLS we namely "measure" the diffusion coefficient of the scattering particles, which gets highly influenced if high-power laser beam is used! High-power laser beam namely locally heats the "scattering volume" in the sample and therefore results in "faulty" diffusion coefficients. Nevertheless this should not be a problem for SLS measurements.

I think we must be used to working with very different samples.  Systems in which multiple scattering might be significant are not something I have gone near, at least not very often. Systems in which the solvent is nonabsorbing but the solute scatters very little light have been more common.  Back before I switched over to pure theory, I would not want to get by with a 20 mW laser, if I could have avoided it, at least not for some experiments. Clearly your systems are quite different.

Thank you all for your answers. 

Some knows what is the prize of zetasizernano?The most sample one!

Thanks!!

Hi Beatriz,

I would recommend contacting the Spanish distributor for Malvern products, IESMAT

They will be able to discuss your application and instrument requirements and advise which model will best suit your needs and relevant pricing information.

https://iesmat.com/catalogo/?actionid=WC_MALZET

Dear Beatriz,

if you are looking for the cheap DLS equipment, you can check out Photocor - Russian-made DLS apparatus with options like advanced avalanche photodiode detector, automated scanning goniometer, and the like. The most simple model should start at about $25000, though it is list price without shipping to Spain.

https://www.photocor.com

This is still a good question.

Perhaps the followers of this thread will be interested in the following 2018 paper that includes a section on light scattering equipment:

https://arxiv.org/pdf/1804.02664.pdf

Beatriz Candas-Estébanez I was able to find data on purchase records for Zetasizer Nano systems online. It looks like the Zetasizer Nano ZS is in the range of €25,000 - 35,000, which is consistent with what others have mentioned. I'm sure the cost varies based on configuration/model variants, and you can get a more precise quote from the vendor.