It is a common phenomenon for most of the nanoparticles to aggregate especially when they are in dried form. For example, the morphology of freeze-dried cellulose nanocrystals was observed to be flake-like compared to the rod/needle-like morphology of never-dried cellulose nanocrystals. Several studies suggested using longer stirring time (24 h or more), tip sonication with higher amplitude considering lower concentration (1wt% or less) of nanocrystals in aqueous suspension as well as use of appropriate surfactants to achieve improved dispersion. However, still, the freeze-dried nanocrystals were found hard to re-disperse in an aqueous medium and get the similar rod/needle-like morphology (like never-dried cellulose nanocrystals).
Any thoughts/suggestions/comments/discussion on this issue????
For longer time preservation as well as for ease of shipment, it is required to freeze-dry the materials.
I understand the need for drying but you cannot win over physics. The material has to be preserved and transported as a suspension, once you dry it; it is no longer a nano entity. The solvent is part of the system, if you get rid of it you are perturbing the system. This is why you observe a flake-like structure, van der Waals forces are kicking in.
I completely agree with your comments ..No doubt that drying causes the aggregation of nanoparticles due to the Van der Waals forces as well as H-bonding (in case of cellulose)..That's why I introduced this discussion to find out the way of breaking down these bonds. If we consider the large scale industrial applications and also the economic aspect, it would not be feasible shipping tons of suspension just for few kg's of nanoparticles. Many Thanks anyway for your comments.
"breaking the bonds" is exactly what you are doing when producing the nanomaterial. H-bonding is a van der Waals force. Regards
Zakir, you can use different types of cryo protectants to protect your material before drying process. Cheers
Great! Also increasing the surface charge can do the trick. Zeta-potential of the CNC particles produced earlier were well below -30 mV, which was the main reason for poor redispersion. Now it is sorted. Thanks everone.
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