To dissolve cobalt ferrite (CoFe₂O₄) and nickel nanoparticles in toluene, consider using surfactants like oleic acid or oleylamine to improve dispersion and prevent aggregation. Additionally, seal the container during mechanical mixing to minimize toluene evaporation and maintain consistent concentration.

Abdelhak Maghchiche I have synthesized nanoparticles in an aqueous medium. So, when synthesized with any surfactant, doesn’t a hydrophilic layer form on the surface of the nanoparticle? Toluene is a hydrophobic liquid. Can a nanoparticle with a hydrophilic surface dissolve in a hydrophobic liquid?

Hi Nushaba Gadirova

Indeed, as you suspect, a nanoparticle with a hydrophilic surface is unlikely to disperse (not "dissolve") in a hydrophobic liquid, which is why the suggestion from Abdelhak Maghchiche makes sense.

However, you may still have the problem of ferromagnetic particles sticking to each other and not just to the magnet. This problem may be alleviated by reducing the particle size. In addition, you can try mixing in a closed cylindrical container on a roller mixer.

You can also try extrusion mixing if you have access to an extrusion mixer. (It probably should be non-magnetic, e.g. stainless steel rather than soft steel). In that case you would use a smaller amount of solvent in order to give your mixture the consistency of a paste, and you may need to work at higher temperature (closer to the PP melting point) and use a solvent much less volatile and flammable than toluene. I suspect you'll need multiple passes. I leave it to you to think about solvent options if you want to use this approach.