My DLS data shows the particle size of my product is 12-15th times bigger than the crystalline size derived from the XRD data. is this normal? please provide some highlights
Thank You..
Hi Gouranga
That's normal, the crystallite size obtained by XDR is the average size of different crystalline domains in a crystal (or particle), usually are smaller that particles size, although in some cases the crystallite and particle size could be the same (if your nanoparticles are small enough).
Regards.
Hi Gouranga,
In addition to the answer given by Hernandes, DLS gives you the hydrodynamic size which can be influenced by the solution used for dispersion. In this sense, sizes given by DLS measurements can be different from the actual size of our particles. So, its recommended to perform some (if possible) Microscopy measurements such as TEM/SEM/AFM.
Best regards.
Nanoparticles are usually monocrystals, so their size should be about the same as a crystal size. To find a cause of discrepancies between your results you definitely need to emply and additional technique, such as TEM or SEM, as was mentioned by Eduardo A. Volnistem You may have agglomerations of nanoparticles (DLS will measure them as single partiles), or you may have big multicrystal microparticles. Or just some mistake was made during measurements.
Gouranga Dutta
You say nothing of your system - are these metal colloids (core-shell) or proteins, for example? How was the sample prepared for XRD and for DLS? Is the material in powder form? (if so then it's not a DLS experiment typically).
As well as different parameters being measured (crystallite-grain-particle) the data are treated in different manners - intensity means from light scattering in DLS and number distributions from microscopy and something even stranger in the 'size' from XRD line broadening. We have core sizes in microscopy and overall particle size (dealing with the protective coatings) in DLS (and yes, aggregates and agglomerates will be seen too in light scattering as they're an overall part of the system. How did you prepare and filter your system for DLS?). Why on earth would you think the results would be similar? Try to think of any situation where the results would be similar... Let us know...
Hello Gouranga Dutta Can you share your DLS data? Light scattering is quite sensitive to the presence of aggregates/dust/air bubbles that can easily skew the average size.
You may find these posts of interest:
- https://www.materials-talks.com/why-does-dls-say-that-my-particles-are-too-small/
- https://www.materials-talks.com/latex-standard-larger-than-on-the-bottle/
- https://www.materials-talks.com/intensity-volume-number-which-size-is-correct/
It is essential that to investigate their crystal/crystalline structures using spectroscopic techniques common place in the nano studies. Then the similarities and differences between particles and their physical and chemical structures will be more obvious to you. I believe that using the existing review articles could be very helpful.
Regards
Gouranga Dutta
The size of the crystalline part of the metal nanoparticle should not differ by 12-15 times from the size of the nanoparticle itself. Therefore, discussion in this direction is useless.
Usually melvien zetasizer DLS consultants pay attention to poor filtration, nanoparticle aggregation, measurement procedure. It's possible. In our practice, we deal with the interaction of nanoparticles with a solvent, mainly water, thermal and quantum fluctuations. DLS is sensitive to all these effects and can lead to a change in the diffusion of the nanoparticle-water aggregate by a factor of 12–15.
Article Structure of Micelles of Sodium Dodecyl Sulphate in Water: a...
Preprint Nuclear quantum effect in aqueous micellar surfactant solutions
The properties of nanoparticles often differ markedly from those of larger particles of the same substance. Since the typical diameter of an atom is between 0.15 and 0.6 nm, a large fraction of the nanoparticle's material lies within a few atomic diameters of its surface.
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