Large Superparamagnetic FeCo Nanocubes for Magnetic Theranostics

Jinming Liu, Kai Wu, Shihai He, Jianmin Bai, Yun Hao Xu, Jian Ping Wang

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


In the past few decades, superparamagnetic nanoparticles (SPMNPs) have attracted increasing attention in a wide range of magnetic theranostics including magnetic biosensors, drug delivery, magnetic separation, magnetic imaging, hyperthermia therapy, and so on. Superparamagnetic iron oxide nanoparticles are currently widely used for these purposes despite their low saturation magnetizations (below 80 emu/g). In pursuit of higher magnetic signals (spatial resolutions) for magnetic imaging, higher sensitivity (limit of detection) for biosensing, higher efficiency, and lower dosage in drug delivery and hyperthermia therapy, magnetic compounds and alloys that generally have higher saturation magnetizations are of interest. FeCo SPMNPs are considered promising candidates for biomedical applications due to their good corrosion resistance, stability, and high saturation magnetizations (over 220 emu/g). However, the critical size for FeCo nanoparticles to be superparamagnetic is limited by a theoretical value of μ15 nm, making it difficult to further increase the magnetic moment per SPMNP. Herein, we report a method to synthesize large single-crystalline FeCo nanoparticle complexes (NPCs) with an overall size of μ100 nm while retaining the superparamagnetic properties. These large FeCo NPCs are synthesized by self-assembling 3 nm FeCo nanoparticle units through a DC sputtering-based gas-phase condensation (GPC) method. By controlling the sputtering parameters like sputtering current density, sputtering pressure, and carrying gas velocity in the GPC system, the nucleation and growth of FeCo nanoparticles can be tuned, and different sizes of nanoparticles can be obtained. The large FeCo NPCs are formed from the second crystallization of small FeCo nanoparticle units with well-aligned crystalline axes, which show both high saturation magnetization and superparamagnetic properties suitable for biomedical applications. It is expected that with the superparamagnetic behavior and higher magnetic moment per FeCo NPC, they can potentially bring higher sensitivities to magnetic biosensors that rely on the magnetic labels, higher efficiency in hyperthermia therapy, and lower dose requirements for magnetic imaging and separation.

Original languageEnglish (US)
JournalACS Applied Nano Materials
StatePublished - Sep 1 2021

Bibliographical note

Funding Information:
Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (award no DMR-2011401) and the NNCI (award no ECCS-2025124) programs. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under Award no ECCS-1542202. The authors thank the Institute of Rock Magnetism, University of Minnesota, for the use of instruments for magnetism measurements.

Publisher Copyright:
© 2021 American Chemical Society.


  • biomedical applications
  • gas-phase condensation
  • high moment
  • nanoparticle complexes
  • superparamagnetic

MRSEC Support

  • Shared


Dive into the research topics of 'Large Superparamagnetic FeCo Nanocubes for Magnetic Theranostics'. Together they form a unique fingerprint.

Cite this