Optimizing the Binding Energy of the Surfactant to Iron Oxide Yields Truly Monodisperse Nanoparticles

Hamed Sharifi Dehsari, Richard Anthony Harris, Anielen Halda Ribeiro, Wolfgang Tremel, Kamal Asadi

Research output: Contribution to journalArticlepeer-review

29 Citations (SciVal)


Despite the great progress in the synthesis of iron oxide nanoparticles (NPs) using a thermal decomposition method, the production of NPs with low polydispersity index is still challenging. In a thermal decomposition synthesis, oleic acid (OAC) and oleylamine (OAM) are used as surfactants. The surfactants bind to the growth species, thereby controlling the reaction kinetics and hence playing a critical role in the final size and size distribution of the NPs. Finding an optimum molar ratio between the surfactants oleic OAC/OAM is therefore crucial. A systematic experimental and theoretical study, however, on the role of the surfactant ratio is still missing. Here, we present a detailed experimental study on the role of the surfactant ratio in size distribution. We found an optimum OAC/OAM ratio of 3 at which the synthesis yielded truly monodisperse (polydispersity less than 7%) iron oxide NPs without employing any post synthesis size-selective procedures. We performed molecular dynamics simulations and showed that the binding energy of oleate to the NP is maximized at an OAC/OAM ratio of 3. The optimum OAC/OAM ratio of 3 is allowed for the control of the NP size with nanometer precision by simply changing the reaction heating rate. The optimum OAC/OAM ratio has no influence on the crystallinity and the superparamagnetic behavior of the Fe3O4 NPs and therefore can be adopted for the scaled-up production of size-controlled monodisperse Fe3O4 NPs.

Original languageEnglish
Pages (from-to)6582-6590
Number of pages9
Issue number22
Publication statusPublished - 5 Jun 2018

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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