New Insights into Amino-Functionalization of Magnetic Nanoplatelets with Silanes and Phosphonates

Abstract

Magnetic nanoplatelets (NPLs) based on barium hexaferrite (BaFe12O19) are suitable for many applications because of their uniaxial magneto-crystalline anisotropy. Novel materials, such as ferroic liquids, magneto-optic composites, and contrast agents for medical diagnostics, were developed by specific surface functionalization of the barium hexaferrite NPLs. Our aim was to amino-functionalize the NPLs’ surfaces towards new materials and applications. The amino-functionalization of oxide surfaces is challenging and has not yet been reported for barium hexaferrite NPLs. We selected two amine ligands with two different anchoring groups: an amino-silane and an amino-phosphonate. We studied the effect of the anchoring group, backbone structure, and processing conditions on the formation of the respective surface coatings. The core and coated NPLs were examined with transmission electron microscopy, and their room-temperature magnetic properties were measured. The formation of coatings was followed by electrokinetic measurements, infrared and mass spectroscopies, and thermogravimetric analysis. The most efficient amino-functionalization was enabled by (i) amino-silanization of the NPLs precoated with amorphous silica with (3-aminopropyl)triethoxysilane and (ii) slow addition of amino-phosphonate (i.e., sodium alendronate) to the acidified NPL suspension at 80 °C.

Insight into (Electro)magnetic Interactions within Facet-Engineered BaFe12O19/TiO2 Magnetic Photocatalysts

“…Moreover, after coating with SiO 2 , a broad, asymmetric signal centered at 1100 cm –1 appeared, which is in very good agreement with the known signals for the analogical silica structures. , A simultaneous shift of the measured ζ potential at a pH of 6 to a strongly negative value further proves successful modification with SiO 2 . During both described procedures, no significant changes in the absorbance characteristic for metal oxides (<700 cm –1 ) are noticed, suggesting that their effect on the structure of BaFe 12 O 19 itself is limited.…”