Synthesis of Fluorous Ferrofluids and Effects of the Nanoparticle Coatings on Field- and Temperature-Dependent Magnetizations

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Fang Chu Lin - , University of California at Los Angeles, California NanoSystems Institute (Author)
  • Heidi L. van de Wouw - , University of California at Los Angeles, California NanoSystems Institute (Author)
  • Otger Campàs - , Chair of Tissue Dynamics, Clusters of Excellence PoL: Physics of Life, Max Planck Institute of Molecular Cell Biology and Genetics, Center for Systems Biology Dresden (CSBD), University of California at Santa Barbara (Author)
  • Ellen M. Sletten - , University of California at Los Angeles, California NanoSystems Institute (Author)
  • Jeffrey I. Zink - , University of California at Los Angeles, California NanoSystems Institute (Author)

Abstract

Ferrofluids have been extensively employed in industrial, environmental, and biomedical areas. Among them, fluorous ferrofluids are of particular interest because of the biorthogonal nature of perfluorocarbons (PFCs). However, the noninteracting nature of PFCs as well as challenges in functionalization of nanoparticle surfaces with fluorous ligands has limited their applications, especially in biomedicine. In particular, commercially available fluorous ferrofluids are stabilized using ionic surfactants with charged groups that physically interact with a wide range of charged biological molecules. In this paper, we developed a unique two-phase ligand attachment strategy to render stable fluorous ferrofluids using nonionic surfactants. The superparamagnetic Fe3O4 or MnFe2O4 core of the magnetic nanoparticles, the magnetic component of the ferrofluid, was coated with a silica shell containing abundant surface hydroxyl groups, thereby enabling the installation of fluorous ligands through stable covalent, neutral, siloxane bonds. We explored chemistry-material relationships between different ligands and PFC solvents and found that low-molecular-weight ligands can assist with the installation of high-molecular-weight ligands (4000-8000 g/mol), allowing us to systematically control the size and thickness of ligand functionalization on the nanoparticle surface. By zero-field-cooled magnetization measurements, we studied how the ligands affect magnetic dipole orientation forces and observed a curve flattening that is only associated with the ferrofluids. This work provided insight into ferrofluids’ dependence on interparticle interactions and contributed a methodology to synthesize fluorous ferrofluids with nonionic surfactants that exhibit both magnetic and chemical stability. We believe that the doped MnFe2O4 fluorous ferrofluid has the highest combination of stability and magnetization reported to date.

Details

Original languageEnglish
Pages (from-to)7957-7966
Number of pages10
JournalChemistry of materials
Volume35
Issue number19
Publication statusPublished - 10 Oct 2023
Peer-reviewedYes