Colloidal Stability of Magnetite Nanoparticles Coated by Oleic Acid and 3-(N,N-Dimethylmyristylammonio)propanesulfonate in Solvents

In order to understand the factors affecting colloidal stability in carrier liquids of different ferrofluids, magnetite nanoparticles coated by surfactants 3-(N,N-dimethylmyristylammonio)propanesulfonate (DP) and oleic acid (OA) were fabricated as dispersions diverse systems. The OA-coated could only be dispersed apolar liquid ( ε r < 5), while DP-coated particles establish a stable system polar base > 5) such water ethanol. solvents was mainly attributed steric repulsion its outer thick shell (∼3 nm). Due absence on solid thin (∼1 nm) magnetite, not liquid. liquid-based form an electric double layer (EDL). total Gibbs interfacial energy analyzed based Van Oss-Chaudhry-Good DLVO theory describe behaviors solvents. case neutral (pH = 7) water-based colloidal, barrier ∼2.2 k B T prevent from precipitation. Bare relatively fragile colloid with ∼1.2 . contrast, exhibited severe phase separation due net attraction ∼ −1.3