Transforming single domain magnetic CoFe2O4 nanoparticles from hydrophobic to hydrophilic by novel mechanochemical ligand exchange

Abstract

Single phase, uniform size (~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 six months, and shows 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.

Valence Change Bipolar Resistive Switching Accompanied With Magnetization Switching in CoFe2O4 Thin Film

“…These oxygen vacancies may reduce some of the Co 2+ ions, leading to the formation of Co 0 ; or, it is also possible that the oxygen vacancies may reduce some of the Fe 3+ ions to Fe 2+ ions, changing the valence of some iron ions. In the CoFe 2 O 4 inverse spinel structure, half of the Fe 3+ ions occupy “A” sites and the other half of the Fe 3+ ions are in “B” sites, whereas the Co 2+ ions resides in the “B” sites 49 . The net magnetization of CFO is given as; M S = M B -M A , where M A and M B are net magnetic moments at “A” and “B” sites 50 .…”

Monodisperse magnetic lecithin-PFP submicron bubbles as dual imaging contrast agents for ultrasound (US) and MRI

“… 15 The oleic acid molecule have tails with both carboxyl group (COO–) and methyl group (CH 3 ) that acts as hydrophilic and hydrophobic groups respectively. 16 As the contrast agent is bimodal, the successful incorporation of SPIONs in lecithin microbubbles lead to a slight increase in water contact angle from 17.9° to 24° but still considered hydrophilic. This hydrophilic surface functionality can help to exploit the potential of T2 based contrast agents as the hydrophilic surfaces can attract neighbouring water molecules with more power than their intermolecular attractive forces between water molecules.…”

SMART RHESINs—Superparamagnetic Magnetite Architecture Made of Phenolic Resin Hollow Spheres Coated with Eu(III) Containing Silica Nanoparticles for Future Quantitative Magnetic Particle Imaging Applications

“…In the second step, the magnetite surface was modified by a ligand exchange process with sodium hydroxide yielding water-dispersible superparamagnetic magnetite NPs (Fe 3 O 4(aq) ). [83,84] In the third step, the magnetite NPs were encapsulated in poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block co-polymer Pluronic P123 (EO 20 PO 70 EO 20 ) and sodium oleate, which formed mixed micelles [71] by hydrophobic interactions, [34] using the soft-template process to generate hollow nanostructures. Subsequently, the polymer shell was formed on the surface of the micelles through weak acid-base interactions by heating after adding 2,4-dihydroxybenzoic acid and hexamethylenetetramine (HMT), [35] yielding Fe 3 O 4(aq) @PFRH.…”