Hello, I am trying to measure the size of PEI by DLS (Zetasizer XS), and I couldn't find refractive index and absorbance values. I actually found that PEI refractive index is 1.66 somewhere but not found absorbance. Do you know any reference for which this information on it?
Thank you in advance.
Hi Alp,
The primary result from a DLS measurement are the Z Average size from Cumulants analysis and the intensity weighted size distribution. Both of these do not need the RI or Absorbance of the material.
These parameters are only used in the conversion of intensity weighted size distribution to number or volume weighted distributions, so if you are unable to measure or find these values, this should not prohibit you doing a meaningful measurement.
Hello Alp Yetisgin , in addition to the above comments you might find this of interest:
https://www.materials-talks.com/blog/2014/08/05/faq-how-important-are-refractive-index-absorption-for-nanoparticles/
Alexander Malm and Ulf Nobbmann thank you for your answers. I can still do a meaningful experiment, so I will do my best.
The refractive Index of Polyethyleneimine is 1.5290
Reference:
https://www.sigmaaldrich.com/SA/en/product/aldrich/408727
I checked the above value of refractive index on sigma aldrich, but doesn't it refer to the refractive index of 50% Aqueous PEI that Sigma Aldrich provides? What would be the refractive index of a thin layer deposited on a substrate?
Hi Krupamaya Nirmal Panda ,
as a first approximation I would suggest the volume average refractive index of the components in your layer, or the whole particle, respectively, if this is for DLS. For example if you layer is composed for ~50% PEI and ~50% water then the referenced value might be an OK approximation.
And again, for standard light scattering results, i.e. cumulant, PDI and intensity size distribution, this is not relevant. Only when converting to a different size distribution is this potentially of interest.
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