Abstract
Amorphous coatings formed with mono-, di-, and tetra-phosphonic acids on barium hexaferrite (BHF) nanoplatelets using various synthesis conditions. The coatings, synthesized in water with di- or tetra-phosphonic acids, were thicker than that could be expected from the ligand size and the surface coverage, as determined by thermogravimetric analysis. Here, we propose a mechanism for coating formation based on direct evidence of the surface dissolution/precipitation of the BHF nanoplatelets. The partial dissolution of the nanoplatelets was observed with atomic-resolution scanning transmission electron microscopy, and the released Fe(III) ions were detected with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy in amorphous coating. The strong chemical interaction between the surface Fe(III) ions with phosphonic ligands induces the dissolution of BHF nanoplatelets and the consequent precipitation of the Fe(III)-phosphonates that assemble into a porous coating. The so-obtained porous nanomagnets are highly responsive to a very weak magnetic field (in the order of Earth’s magnetic field) at room temperature, which is a major advantage over the classic mesoporous nanomaterials and metal–organo-phosphonic frameworks with only a weak magnetic response at a few kelvins. The combination of porosity with the intrinsic magneto-crystalline anisotropy of BHF can be exploited, for example, as sorbents for heavy metals from contaminated water.
Highlights
Barium hexaferrite (BHF; BaFe12O19) is traditionally used for permanent magnet and microwave technology applications.[1]
Amorphous coatings formed on the barium hexaferrite nanoplatelets (BHF NPLs) from different phosphonic acids: ethylenediaminetetra(methylenephosphonic acid) (EDTMP), octadecylphosphonic acid (OPA), (12-phosphono)dodecyl phosphonic acid (DPA), and (12-phosphono)dodecyl sulfonic acid (PSA)
Ca. 1−2 nm thick, coatings were obtained with monophosphonic acids, Octadecylphosphonic acid (OPA) and PSA, that assembled in a bilayer on the BHF NPLs surfaces
Summary
Barium hexaferrite (BHF; BaFe12O19) is traditionally used for permanent magnet and microwave technology applications.[1] the development of a hydrothermal synthesis for its production in nanoform[2,3] led to a new material, ferromagnetic liquids,[4,5] and opened up a variety of new application possibilities[6−9] in magneto-optics, magneto-rheology, spin memory devices, bioimaging, catalysis, and magneto-mechanical cancer treatment These new applications arise from the intrinsically anisotropic magnetic properties of the BHF nanoplatelets (NPLs) that allow for their alignment at a very low magnetic field, i.e., below 1 mT. We propose the formation of a porous phase by coating the BHF NPLs with phosphonic acids
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
