I want to measure the size of asphaltene nanoaggregates in toluene solution. Sample concentration is 0.12 mg/l . Asphaltene is completely miscible in toluene and hence not a suspension.
Yes. See papers with a GoogleScholar search. I believe it's dynamic not dyamic...
Yes. DLS will measure the diffusion coefficient of the particles. Knowing the viscosity of the solvent then allows you to calculate the hydrodynamic radius.
In the toluene formed asphaltene associates. About five fused benzene rings are assembled in a stack one above another with approximately parallel planes. On the periphery of these drives are attached aliphatic or naphthenic hydrocarbons. Dimensions associates 1,4-3,5 nm.
Best regards.
Yes you can measure the nanoparticle size as well as zeta potential (In most of the DLS system, they have the option to measure zeta potential)
Dissolved means no particles. Would assume that in case of asphaltenes you mostly have both particles and dissolved complexes. For both DLS should be able to determine a size value.
Yes, it can and has been done with dynamic light scattering DLS.
Just as an illustration of how small DLS can measure, it can detect sucrose molecules in water. One "trick" is that there needs to e enough scattering signal from the small component to be detectable.
http://www.materials-talks.com/blog/2015/02/20/on-the-mystery-of-nanoparticles-in-sucrose/
http://link.springer.com/content/pdf/10.1007%2Fs11051-007-9317-4.pdf
http://www.materials-talks.com/blog/2016/01/21/zetasizer-sensitivity-for-protein-dls/
Dynamic Light Scattering will not be applicable for very small particles (lower than 4 nm) because of light scattering confinement in this scales. when you dissolved your particle you just have the asphaltene molecules disspersed in solvent. so based on your DLS set up you may have some sizes less than 10 nm. If you try DLS to analyzed the dissolved nanopaticles I really want to see the results for more interpretation.
I do not think that a material when gets dissolved completely in a solvent that is too in such a small quantity (0.12 mg/l), it could remain remain in nanocrystalline form. Rather, it would be in ionic form or some radicals may be formed. I don't think their sizes could be measured by DLS.
--- P D Sahare
A molecule is a particle to light scattering - it does not have to be crystalline to scatter light. Think of the blue and red skies (caused by scattering of O2 and N2 molecules (and dust) in the atmosphere). The measurement of the (correct) size of molecules such as sucrose, vitamin B12 and many others by DLS shows its applicability in this area.
@Alan F Rawle: Dear Prof. you are right about light scattering caused by molecule. But based on Mie theory small particles and molecules scatter light in every angle and in very low intensity also scattering intensity fluctuates over time. So mentioned confinements is some of main reason for DLS limitation for very small particles or molecules.
@ Seyed Mohammad Amini Yes, Mie theory correctly predicts the isotropic scattering from small molecules (the Rayleigh approximation works well for particles or molecules less than one-tenth the size of the incident radiation). And yes, the scattering is low - that's why individual photons are counted in DLS experiments. The fluctuation with time is the basis of DLS and the correlogram - small molecules or particles lose their information more rapidly than larger entities. You'll find plenty of literature references to DLS of molecules from small molecules such as lysosyme or BSA down to larger molecules such as vitamin B12 and cholesterol. So, modern researchers do not see limitation with DLS for such molecules. However, as larger particles and molecules scatter more intensely, then cleanliness of the system becomes very important the smaller we wich to measure,
Since DLS is based time dependant intensity fluctuations, you can get information about hydrodynamic size. If the scattering intensity due to the scatterer (at the concentration studied) is at least 10 times more than the background solvent signal, you should be able get a correlogram.
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