ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Magnetic fluids’ stability improved by oleic acid bilayer-coated structure via one-pot synthesis

Ming-Jie Chen, Hui Shen, Xin Li, Jin Ruan, and Wei-Qin Yuan

Department of Materials Science and Engineering, College of Materials and Energy, South China Agricultural University, Wu Shan Street, Guangzhou 510640, China

E-mail: 234659747@qq.com

Abstract: To improve the magnetic fluids’ stability and demonstrate the relationships between the bilayer-coated structure and the stability, a simple method was proposed for preparingoleic acid bilayer-coated Fe₃O₄ magnetic fluids. The hydrophilic Fe₃O₄ nanoparticles coated with the bilayer-oleic acid were synthesised by a one-pot process through the chemical co-precipitation under alkaline conditions. Next, the hydrophilic Fe₃O₄ particles were transformed to hydrophobic particles via carboxyl-protonated modification. Carboxyl-protonated modification was found to be a reversible process, i.e. the lipophilicity of the coated Fe3O4 nanoparticles could be controlled by protonating/deprotonating the terminal carboxyl group. In addition, the space steric effect could be significantly enhanced by maximising the oleic acid adsorption and increasing the thickness of the coated layer, resulting in the oleic acid bilayer-coated Fe3O4 nanoparticles exhibiting better performance in the stability of the hexanemagnetic fluids than oleic acid monolayer-coated Fe₃O₄ nanoparticles.

Keywords: protonated modification; Fe3O4 nanoparticles; oleic acid; bilayer-coated structure; hexane magnetic fluids

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2016-0096

Chemical Papers 70 (12) 1642–1648 (2016)