| Author | Message | ||
     Xuxin Lai (laixuxin) Junior Member Username: laixuxin Post Number: 16 Registered: 6-2004 |
Yavor, When I measured my sample in NIR, I got a very large baseline shift in the range of 700-1300nm, and it is due to light scattering effect, because MSC can easily correct it, so I choose this wavelength range. You can start to measure your sample by NIR, and see what happen in 700-1300nm. I think you can use 0.5cm pathlength cuvette as sample holder, and you should try serveral concentrations. I don't know why you choose NIR for the particle size determination of your samples. Actually, other particle sizing methods/instruments, such as laser diffraction, dynamic light scattering and single particle optical sensing should be a better choice, especialy if you need to know the particle size distribution. Using NIR, you can only get the mean particle size. But there are several kind of mean particle size, such as volume weighted mean, surface weighted mean, or particle weighted mean. But from our experiment, our NIR particle size is mass weighted mean. As Gabi Levin said, you need to find out the relationship between the wavelength and particle size. I think Mie theory is a suitable one, but it is not easy to understand. As to the low limit of the particle size, I think it might be 100nm. Anyway, I think you can see the size change from 100nm to 1500nm in the wavelength range of 700-1300nm. You may use polystyreen particle size standard to see if your NIR instrument can do it. I hope this can be a little help to your project. Best regards, Xuxin | ||
| Gavriel Levin (levin) Senior Member Username: levin Post Number: 40 Registered: 1-2006 |
Hi Mr. Yavor, To get an answer you should first go to the basic equations of the scattering effect outlying the relation between wave length and particle size. This will give you an idea of the magnitude expected. The next thing is to find what wavelength laser the manufacturers of such equipment would use for the nano particle size that you describe. This will give you an idea if the wavelength range 700 to 1100 can be useful or not, 200 nm is not a full scale nano size - it is still on the very hign side of nano. If you are looking to determine distribution as well as size range than in any event NIR is not a sharp enough tool to tell you distribution, regardless of the size range you are working with. Is the suspension transparent to visible or is it very opaque? Gabi Levin | ||
| Kamdzhilov Yavor (nir_greenhorn) New member Username: nir_greenhorn Post Number: 4 Registered: 5-2007 |
Dear Xuxin, Thanks for your answer. Yes, I presume the material has absorption in the 2v and 3v range (it is an organic molecule) although it might be very week due to the lower probability of these transitions. But that might not be the point. I naturally counted more on scatter effects than absorption. For the light to scatter you have got a lower limit related to the wavelength and the PS. On what bases do you define 700-1300 nm range as a useful one? Do you think I can get a hold on your results? (if not protected by patents, and all that) Best, Yavor | ||
| Xuxin Lai (laixuxin) New member Username: laixuxin Post Number: 15 Registered: 6-2004 |
Yavor, I think you can use the light scattering effect in 700-1300nm to determine the particle size in water suspension by transmittance NIR. Do you know if the material have absorption peak in this wavelength range? I have done a similar study on the particle size determination in suspension. NIR works nicely. Best regards, Xuxin | ||
| Kamdzhilov Yavor (nir_greenhorn) New member Username: nir_greenhorn Post Number: 3 Registered: 5-2007 |
Dear All, Has anybody heard/read anything about particle size determination of nano-particles by NIR? There is not much in the literature and I keep thinking that there is not going to be much of a scatter from a water suspension of nano-particles (size ca. 200 nm) due to pure physical reasons. As the solution is aqueous there might be some matrix effects though.( I have to talk to Rumiana perhaps). What do you think? Best, Yavor ps. The NIR 2007 was a wonderful event! Congrats to the community! |