As it is well known fact that nano-particles can easily aggregate during nucleation/ synthesis part due to high surface energy..by reading literature, I came to know that surfactants can help to prevent this but is there any other method by which we can prevent aggregation of nano-particles without using chemical surfactants?.. Thank you in advance for your valueable time, suggestions and help. ..
Dear all, a lot of work is done on the powerfull effect of ultrasound and microwaves on nanoparticles aggregation control, so may be this is usefull to investigate in your work. My Regards
hi,
Fundamentally it is not possible to inhibit the aggregation of the nanoparticles. The unbalanced electromagnetic forces from the atoms dominates on the kinematics of the matter as the size is reduced to sub micron dimensions. Hence no matter what one will always endup with aggregation of the nanoparticles when they are in suspended in an medium without using any sort of surfactant. All you can do is reduced the speed of their aggregation by using surfactant, but after sufficiently long passage of time, irrespective of the type of surfactant used, aggregation is inevitable.
Regards
Amit
Dear all, a lot of work is done on the powerfull effect of ultrasound and microwaves on nanoparticles aggregation control, so may be this is usefull to investigate in your work. My Regards
An essential parameter that determine the stability of a nanoparticle dispersion is their surface charge. Depending on the NP type and preparation method, such charge can be provided to the NP surface without adding specific surfactants.
A typical example is Ag nanoparticles in water produced by laser ablation in liquids, that is without any precursor. In that case the "bar" nanoparticles have a negative surface charge (due to a very thin Ag oxide layer on their surface) able to polarize the H2O medium and favors the mutual separation among NPs. The stability, in proper but easily achieved storage conditions, may reach several months. If the nanoparticles are capped with some polymer layer, such as PVP or PEI, their surface charge can be tailored and modified from negative to positive, but still allowing long or very long (even years) stability in storage. In the latter case, the polymer must not be confused witha asurfactant, being PVP, PEI or any other capping agent a fixed component of the nanoparticle as a whole, like a sort of core-shell particle.
It depends if you synthesize your nanoparticles it in the gas or aqueous phase. In general if you are able to lower the surface energy by any means such as lowering the temperature in gas phase synthesis, the particles will no longer be as likely to aggregate. Furthermore, if your number concentration of particles is lower than a certain value (~10^7 part / cm^3), the time that is required for them to collide, agglomerate and grow also increases.
In addition to the above said. If you really do not need a surfactant in your nanoparticles while keeping their not (or weakly) agglomerated state you can try adding small quantity of volatile organic compounds (VOC like pyridine or similar, it depends on nature, size of the NPs) into a dispersion of these nanoparticles in a solvent. These VOC are easily removable upon drying the NPs
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