I have synthesized plain mesoporous silica nanoparticles by sol-gel method. After synthesis disperesed particles into di water, methanol and ethanol for dls. what could be the reason conclusion by this? what can i change in synthesis?
Amber Bano
Thank you for posting your question. I'll try to help but I think it would be best and possibly quicker to contact your local support in Pakistan as there are many things to discuss. Alternatively please post your .dts data file on this site or to: https://www.materials-talks.com/blog/2014/08/19/faq-how-can-i-submit-a-data-file-to-the-help-desk/
Please tell us more about your sample(s). Is it prepared and retained in suspension? Or have you dried it and re-suspended it? Please post a picture of your sample in the cuvette so we can see it.
The .dts file is much smaller than posted reports (which are useful but may not tell the entire story) and allow more conclusive comments to be made. OK, where to start?
Let's look at the DLS results. All your reports say 'Refer to Quality Report'. This is another tab and will give you more clues as to what is wrong as will the 'Expert Advice' tab. I attach an older application note which tells you some of the tests that are applied that decide if a result is good or poor. However, some pertinent points:
- The measurement position is 4.65 mm (which is the center of the cell) but you have an attenuator of 7. Assuming this is an automatic setting then this tells me that there's nothing in the system. Has your material settled or sedimented? Is it too large for DLS? Is is better for laser diffraction? Does your sample need dilution? I can't tell these things simply from a print out and that's why the ,dts data file will be more helpful. We have a manual setting sop (rather than the automatic) and I can't tell what's been altered from the automatic (preferred) settings. What does the correlogram look like? I assume with the thin peak that we'll see an appalling fit and the far field rising from the sedimenting particles. Have you waited sufficient time for temperature equilibrium?
- The z-average (> 1 um) and PDI (= 1.000) tell me that the size distribution is large and broad and probably settling and that the sample is probably unsuited to DLS and that laser diffraction is a better bet
- Although the refractive index of the particle is not needed for an intensity distribution, the imaginary/absorption setting of 0 is only possible for a homogenous transparent sphere (ISO13320:2020 Section 6.6.3) and I don't think you material is this, is it?
- Attenuator 4 on the zeta run is a concentrated sample. You have movement (electrophoretic mobility) which is easily detected but it's probably hindered in this concentrated environment and thus conversion to a ZP is probably ill-advised in this case
- Not sure why sample names of methanol are used but the dispersant shown is water Bottom pf page 3/top page 4). Pease explain.
- Intercepts of > 1.00 show some issues in the sample. Again the .dts file will help understand these issues
That's enough for now. We need some more data (not reports) to be able to help further and this is much slower on RG than it would be locally
Amber Bano
If you've dried your particles then it's a laser diffraction, not a DLS experiment as you do not have free, independent, discrete particles < 100 nm. Please see this webinar (registration required):
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
Yes its correct that the final form of my synthesized particles after washing of mesoporous silica is amorphous. To perform DLS i prepare nanoparticle dispersion in the solvents just before analysis. Alan F Rawle
Amber Bano
You’ve said very little but I suspect your material is in the microns plus size and unsuited to DLS. It’s sedimenting in the cuvette and sitting on the bottom. You can’t re-disperse a powder to ‘nano’. Look at the webinar in my second answer. From 2 others greater than I:
Rudy Rucker: 'I think dry nanotechnology is probably a dead-end' Transhumanity magazine (August 2002)
Jim Adair: 'If the particles are agglomerated and sub-micron it may be impossible to adequately disperse the particles…… The energy barrier to redispersion is greater if the particles have been dried. Therefore the primary particles must remain dispersed in water….' J H Adair, E. Suvaci, J Sindel, “Surface and Colloid Chemistry” Encyclopedia of materials: Science and Technology pp 8996 - 9006 Elsevier Science Ltd. 2001 ISBN 0-08-0431526
Your DLS data show quite large PDI values. This indicates that a simple z-average size does not describe the situation well. Most likely there are much larger particles present. These contribute a lot of signal to the correlation function.
You may also like this blog comparing the peak size and the z-average size http://www.materials-talks.com/blog/2014/07/10/faq-peak-size-or-z-average-size-which-one-to-pick-in-dls/
You are not describing the synthesis technique, but asking how to change the synthesis. The sol-gel method is very capricious and the slightest inaccuracy can lead to poor results.
Will you help me how to take weight calculations.
how to make solutions.
any formulas....
Yuri Mirgorod (A) The surfactant (CTAB) is dissolved in water. (B) BASE was added and stirred (C) Silica precursor is then added dropwise and condensed around the surfactant template.
Amber Bano
Nanosilica can be synthesized from alkoxysilanes , silicon tetrachloride. A sol-gel assumes the hydrolysis of alkoxysilanes (a sol is obtained), then polycondensation is carried out (converted into a gel), the gel is calcined, and the nanoparticles are washed. If the dispersion prepared from nanoparticles is not stable, then a certain amount of surfactant is added so that there is no excess. Otherwise, with an excess of surfactants, micelles are formed. How you synthesized is still not clear. The presence of sol, gel, surfactant micelles can and even associates of these products with water can be perceived by the device as nanoparticles.
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