WG: [RASMB] nanoparticles

[wendel.wohlleben at basf.com]

Dear Louise,

yes, we have characterized lots of these and other nanoparticles with the
AUC. There is an excellent overview on this topic by Helmut Cölfen in the
2005 AUC-book.

1) Since inorganic particles have rather high dn/dc, scattering starts at
small diameters. When measuring agglomerates, you may have to dilute
enormously to get light through to the interference detector. The
Interference detector is much more reliable. The absorption signal is not
proportional to mass fraction, but instead is weighted by turbidity. In
fact, time-scanning turbidity detectors at fixed radius are sometimes even
more preferrable: They capture the entire bunch of agglomerates up to µm,
and they see the primary particles down to ~15nm.
2) Because of polydispersity from association or agglomeration you may not
capture the entire distribution at a single speed. We measure in the same
cell successively at increasing speeds. You can log/log-plot the multiple
size distributions and thus construct the entire distribution.
3) Density is in general not known. Even inside the nanoparticle, many of
them do not reach bulk density, and additionally comes the effect of the
surface layers. We normally calculate with the bulk density anyway, knowing
from comparison with TEM that we tend to underestimate the diameter by some
10%.
4) I can only support Arthur that ls-g(s*) is the approriate fitting
algorithm. Diffusion is very weak, especially when you work with fast
speeds and the interference detector.


Beste Grüße, Wendel


Dr. Wendel Wohlleben
Polymer Physics


Phone: +49 621 60-95339, E-Mail: wendel.wohlleben at basf.com
Postal Address: BASF Aktiengesellschaft, GKP/O - G201, D-67056
Ludwigshafen, Germany


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             Louise Creagh                                                 
             <alcreagh at chml.ub                                             
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                                                                     Thema 
                                        [RASMB] nanoparticles              
             24.10.2006 21:31                                              
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Hello,
Does anyone have experience in running samples containing nanoparticles
(30 nm diameter; copper, iron, silver or gold) in aqueous buffer
solutions on the XL-I?
Thank you.
Louise Creagh.
University of British Columbia.

--
Louise Creagh


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