For the particle size distribution measurement via laser diffraction in the
@ Nicolas Thank you for your question.
ISO13320:2009 tells you that the optical properties become important where d < 40 lambda, where d is the diameter of the particle and lambda the wavelength of the impinging radiation. This would be around 25 microns for a He-Ne laser of 632.8 nm. Indeed for glass spheres (NBS1003c) an incorrect opaque assumption (Mrs Nadia Hofer) will generate a false proportion of fines in the 1 - 2 micron region and this is for 40 micron x50 material. So, your assumption of needing Mie theory only in the < 1 micron region is a little suspect. Indeed an exact knowledge of the optical properties is not required if there is robustness in the variation of optical properties (and if the relative refractive index is 'high') and this is easily tested (see later). A nanoparticle dispersion with 100% < 100 nm will be optically clear (may be colored like a gold sol) and thus not non-transparent which hints at material in the sub-micron (100 - 1000 nm) region at best. If the (wetted) material is settling in water under gravity then it's not a nanoparticle dispersion. Period.
In general terms the real part of the RI is required to 2 decimal places only and the imaginary absorptive part to an order of magnitude. The real part of the RI can always be measured, Zero imaginary is only possible for a homogeneous transparent sphere (ISO13320:2009 Section 6.6.3) so generally we'd only need to consider 0.001, 0.01, 0.1, and 1.0 for a robustness study. If you're looking at your industry (carbon) then clearly (bad pun) the imaginary is likely to be high. For the various forms of carbon, literature references for the RI are easily found and a robustness study easily undertaken.
For a little more on robustness and the determination/measurement of the imaginary see the following webinar and the references therein:
Determination of the optical properties of CeO2 and CaCO3 by the volume concentration experiment - the 3 S's, Beer-Lambert and Mie https://www.brainshark.com/malvern/vu?pi=zF2zI6Y3fz5chz0&tx=preview
Open in IE only and this is not enabled for mobile viewing. NOTE (090420) - this link is no longer functional. See my answer below.
If you have a Malvern laser diffraction instrument then you have wonderful support from Malvern Panalytical GmbH.
For DLS experiments then the optical properties are not needed for an intensity distribution. Also look at:
http://www.materials-talks.com/blog/2014/08/05/faq-how-important-are-refractive-index-absorption-for-nanoparticles/
@ Nicolas Thank you for your question.
ISO13320:2009 tells you that the optical properties become important where d < 40 lambda, where d is the diameter of the particle and lambda the wavelength of the impinging radiation. This would be around 25 microns for a He-Ne laser of 632.8 nm. Indeed for glass spheres (NBS1003c) an incorrect opaque assumption (Mrs Nadia Hofer) will generate a false proportion of fines in the 1 - 2 micron region and this is for 40 micron x50 material. So, your assumption of needing Mie theory only in the < 1 micron region is a little suspect. Indeed an exact knowledge of the optical properties is not required if there is robustness in the variation of optical properties (and if the relative refractive index is 'high') and this is easily tested (see later). A nanoparticle dispersion with 100% < 100 nm will be optically clear (may be colored like a gold sol) and thus not non-transparent which hints at material in the sub-micron (100 - 1000 nm) region at best. If the (wetted) material is settling in water under gravity then it's not a nanoparticle dispersion. Period.
In general terms the real part of the RI is required to 2 decimal places only and the imaginary absorptive part to an order of magnitude. The real part of the RI can always be measured, Zero imaginary is only possible for a homogeneous transparent sphere (ISO13320:2009 Section 6.6.3) so generally we'd only need to consider 0.001, 0.01, 0.1, and 1.0 for a robustness study. If you're looking at your industry (carbon) then clearly (bad pun) the imaginary is likely to be high. For the various forms of carbon, literature references for the RI are easily found and a robustness study easily undertaken.
For a little more on robustness and the determination/measurement of the imaginary see the following webinar and the references therein:
Determination of the optical properties of CeO2 and CaCO3 by the volume concentration experiment - the 3 S's, Beer-Lambert and Mie https://www.brainshark.com/malvern/vu?pi=zF2zI6Y3fz5chz0&tx=preview
Open in IE only and this is not enabled for mobile viewing. NOTE (090420) - this link is no longer functional. See my answer below.
If you have a Malvern laser diffraction instrument then you have wonderful support from Malvern Panalytical GmbH.
For DLS experiments then the optical properties are not needed for an intensity distribution. Also look at:
http://www.materials-talks.com/blog/2014/08/05/faq-how-important-are-refractive-index-absorption-for-nanoparticles/
Getting up to 2 years since the posting of the question and the poster never returned.
Dear Alan F Rawle ,
it is a pitty that a lot of asking persons never return to their questions.
It should be a matter of politeness to do that;
either by a recommendation to the answers or at least by a simple 'thank you'.
I have experienced such a behaviour of lot of times.
And it is not only restricted to low RG-score people...
I have yet filed a discussion on this topic:
https://www.researchgate.net/post/People_asking_questions_here_on_researchgate_often_do_not_feed_back_to_answers_at_all
Hi Alan
Really nice answer, and a big thank you from me and on behalf of Nicolas who never turned back, but please keep doing nice work like this. Thanks again and I will see this post again in Sept 2021
Kunal Kadiya Thank you for your kind comments. I have one correction to make in my answer above. In the 2 years passing since the question was asked then our relationship with Brainshark has ceased and the provided url does not work. Many webinars migrated over but this wasn't one. However...
Most of the important content was incorporated in the last (the first below) of 3 recent optical property webinars (registration needed):
- Laser Diffraction Masterclass 3: Optical Properties - How Can Material Optical Properties be Measured https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200414OpticalProp.html
- Laser Diffraction Masterclass 2: How Can Material Optical Properties be Calculated/Estimated https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200317LDBasics2.html
- Laser Diffraction Masterclass: Why do you Need Material Optical Properties? https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200211LDBasics1.html
Also, the CeO2/CaCO3 webinar is being revamped for future use, so it will see the light of day again sometime in the future.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructured Materials
- Nanoparticles