As mentioned above, I have tried to disperse MNPs (Fe3O4 , 20nm, powder ) in water/kerosene (added some ammonia and 3% of oleic acid ) to make it stable and without sedimentation .
I heated up the fluid to 110oC for 5 min hoping the MNPs is coated with surfactant ,turned out there's still a lot of aggregation at the bottom.
the question is that is it possible to coat the ready-made MNPs with oleic acid, how and why
You want to make a dispersion of magnetite nanoparticles in kerosene. This dispersion is called magnetic fluid. Add water and ammonia is not necessary. Oleic acid acts as a stabilizer of magnetite nanoparticles. It is adsorbed by the carboxyl group on the surface, because carboxyl group reacts with iron ion on the surface of the nanoparticles. How much add oleic acid? Each acid molecule occupies an area of 0.21 nm2. There must be a minimum monomolecular layer. Therefore, you can calculate the amount of acid. Add, mix. Heat is not necessary. When heated, the adsorption of acid on the surface of the nanoparticles decreases.
Dear Yuri Mirgorod :
thanks for your answer.
in order to know how much oleic acid i need,is there any reference about how acid molecule occupies the surface area of nanoparticles?
one more question, does the mixing time matters? how much time does the reaction between acid and nanoparticles take ?
I explain all your questions to my students at lectures. Explain on the fields of RG is impossible. Read the relevant sections of colloid chemistry. In order to simplify the entrance to colloid chemistry, I attach my methodological instruction for students, but in Russian. For you it is marked in red in the section adsorption. To mix enough 0.5 hours.
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