I am preparing magnetic iron oxide nanoparticles for drug delivery purposes so after preparation I need to disperse the particles by sonication to negate the aggregation of particles. I uase 40mg/ml of particles in ph-8.9 but even after 120 min sonication they are not fully dispersed. Bsed on other reports after sonication the colour changes fro dark to brown and you can not see any particles inside the solution but for my case nothing is changed after sonication as well. Could you please give me some hints -1 how to disperse the poarticles fully and 2- why the colour of particles changes from blak to brown? Best
Are the particles dried? What is their size? Perhaps you are dispersing too much particles (assuming that we are not dealing with dried nanoparticles). What is the zeta potential of the particles?
Hi There and thanks for the comment.
particles are dry and I also sonicated the paricles freshly prepared after 30 min drying but no noticable changes! The size is less than 15 nm based on TEM and 200-300 nm in zeta sizer( different pHs). Zeta potential is 6.7. I am not 100% sure but maybe the probe sonication am using is not strong enough for fully disperssing!
If the particles were dried it will be almost impossible to fully disperse them. What are the units of the zeta potential? If it is mV; they are not stable to begin with.
Dear Hetemadi,
Dried nanoparticles are very difficult to be re-dispersed in solvent, especially iron oxide nanoparticles. I would suggest you to maintain the as-synthesized nanoparticles in aqeuous solution without drying for future experiments.
Probe sonication must not be carried out for magnetic nanoparticles since the probe would attract the magnetic nanoparticles.
Also, 40 mg/mL is a very high concentration considering iron oxide nanoparticle dispersion in water. I would suggest you to try dispersing much lesser concentration 1 mg/mL using bath sonicator.
It might be effective if you added some capping material during the preparation procedure aiming to reduce the effect of agglomeration.
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