Transforming single domain magnetic CoFe^sub 2^O^sub 4^ nanoparticles from hydrophobic to hydrophilic by novel mechanochemical ligand exchange

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2017-01, Vol.19 (1), p.1
• Main Authors: Munjal, Sandeep, Khare, Neeraj
• Format: Article
• Language: English
• Subjects: Cobalt; Nanoparticles; Zeta potential
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-016-3700-y

Single-phase uniform-sized (~9 nm) cobalt ferrite (CFO) nanoparticles have been synthesized by hydrothermal synthesis using oleic acid as a surfactant. The as-synthesized oleic acid-coated CFO (OA-CFO) nanoparticles were well dispersible in nonpolar solvents but not dispersible in water. The OA-CFO nanoparticles have been successfully transformed to highly water-dispersible citric acid-coated CFO (CA-CFO) nanoparticles using a novel single-step ligand exchange process by mechanochemical milling, in which small chain citric acid molecules replace the original large chain oleic acid molecules available on CFO nanoparticles. The OA-CFO nanoparticle's hexane solution and CA-CFO nanoparticle's water solution remain stable even after 6 months and show no agglomeration and their dispersion stability was confirmed by zeta-potential measurements. The contact angle measurement shows that OA-CFO nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic in nature. The potentiality of as-synthesized OA-CFO and mechanochemically transformed CA-CFO nanoparticles for the demulsification of highly stabilized water-in-oil and oil-in-water emulsions has been demonstrated.