![]() ![]() You don't have easy access to the tool, so instead of finding a way to get that access, you're trying to invent a new method to do the same thing. ![]() Old post but I have a lot of DLS and nano/sol experience.ĭLS is the right tool for the job. Tl:dr can I build a makeshift DLS setup that determines minumum particle size? So before I go ahead with all of this, do you think it will work? Any tips, pointers or suggestions? DLS is not my field so any help is beneficial. I'm chatting bollocks and it just wont work with the apparatus I've got not accurate/precise enough. The vibration due to the sonication itself would adversely affect brownian motion (I may just have to stop sonicating, do DLS and then sonicate again) At this stage, the maximum frequency would be the stage at which the particles were smallest and could not get any smaller (fully dispersed). If I did this in situ of the sonication, the frequency would increase until it hit it's maxima. My hypothesis is shining the laser through the sample, and detecting the scattered light with a photodetector I will receive a frequency relative to the particle size due to brownian motion (bigger conglomerates move slower, rate of scattering is low - smaller conglomerates move faster, rate of scattering is high). Luckily, we do have a deep UV (~220nm) laser and I can easily get a photodetector and oscilloscope. After doing some research I wonder if I can build a setup that while cannot determine actual particle size would determine the stage at which the minimum particle size was achieved. DLS seems to be the right way of going about it but we don't have a DLS machine in the lab. I'd like to determine the point at which the nanostructures are fully dispersed within the solution, so as to know the optimal minimal length of time sonication is required. Now I'm sure it would be fine to just to sonicate each sample for as long as possible but it's hardly scientific. Now all these nanoparticles are unfavorably entangled and to disperse the particle conglomerates we have been sonicating each sample. It simply means that you have to be sure that the relaxation of the fluctuations of the scattered intensity comes from the translational Brownian motion of the particles and not from the relaxation of their internal structure (if q is too big).So here's my problem: I have samples of carbon nanostructures (primarily a mix of carbon nanotubes/onions etc) in a solution of methanol. This limit depends on the kind of particle you probe (with or without internal dynamics). Any way, you have to be sure that the measurement of tau is made in the limit q.R<<1. Considering the minimum tau, you have a combination of D and q (using previous equations) that could correspond to it and you can derived the minimum size measurable. What is the minimum relaxation time that can be measured with a given apparatus ? This is the main limit. The main limit is from my point of view the sensitivity of the correlator. The combination of both determines the accessible length scale (q^-1) and then the relaxation time measured for a given diffusion coefficient D (see equations in my previous message). The wave length (lambda) is important but the angle of measurement (theta) is also very important. Dynamic scattering techniques give information about dynamics of the solution and under certain conditions give access to the hydrodynamic radius of particles. Using "dynamic" X-ray scattering (XPCS) is only possible on large facilities (like ESRF in Europe) and is not accessible in a regular lab. These fluctuations being related to concentration fluctuations in the solution. It monitors fluctuations of the scattered intensity (or electric field) by the solution. ![]() DLS is often called QELS (quasi elastic ligth scattering) or PCS (photon correlation spectroscopy).
0 Comments
Leave a Reply. |