Formation of Fe(III)-phosphonate Coatings on Barium Hexaferrite Nanoplatelets for Porous Nanomagnets
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 cov...
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| Published in: | ACS omega Vol. 5; no. 23; pp. 14086 - 14095 |
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| Main Authors: | , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
American Chemical Society
16-06-2020
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| Online Access: | Get full text |
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| Summary: | 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. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 2470-1343 2470-1343 |
| DOI: | 10.1021/acsomega.0c01597 |