Interaction mechanism between Fe₃O₄ nanoparticles and sodium 2-dodecyl- benzenesulfonate

In the paper, the dispersion stability of Fe₃O₄ nanoparticles in water by ball milling with surfactant sodium 2- dodecylbenzenesulfonate (SDBS) was studied. The ball milling time as influence factor on the stability of magnetic fluid was investi- gated. Then, the nano-Fe₃O₄ magnetic fluid was prepared and characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), particle size analyzer, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results show that the best time of ball milling is about 5h. The stably dispersed Fe₃O₄ mean size is about 34.1 nm. SDBS is adsorbed on the surface of nanoparticles by chemical bonds. SDBS covers Fe₃O₄ nanoparticles through sulfonate group links. Then another SDBS continues to adsorb by physical forces to disperse stably in the water solution by the steric hindrance and electrostatic effect.