Vacancy ordered maghemite (γ-Fe 2 O 3 ) nanoparticles functionalized with nanohydroxyapatite (HAp – Ca 10 (PO 4 ) 6 (OH) 2 ) have been successfully synthesized using an inexpensive co-precipitation chemical route. Evidence for the presence of vacancy order in maghemite was shown by the superstructure lines observed in X-ray diffraction. The adsorption of carboxyl groups of citric acid (C 6 H 8 O 7 ) onto γ-Fe 2 O 3 nanoparticles was investigated by FTIR, XPS and Mössbauer spectroscopy. From XPS surface analysis, two binding energies related to oxygen were attributed to bindings between C 6 H 8 O 7 /γ- Fe 2 O 3 and C 6 H 8 O 7 /HAp from an interfacial reaction promoted by strongly adsorbed H 2 O molecules at the surface of these nanomaterials. Le Bail refinement of the XRD patterns showed the formation of well-crystallized pure tetragonal maghemite before and after functionalization with nanoHAp. The temperature dependence of hyperfine parameters of pure and functionalized γ-Fe 2 O 3 nanoparticles was investigated via Mössbauer spectroscopy. TEM revealed the formation of quasi-spherical γ- Fe 2 O 3 nanoparticles with an average diameter of ca. 12 nm and 16 nm before and after functionalization with nanoHAp in agreement with Le Bail refinement. Magnetometry measurements showed a saturation magnetization of 12 emu/g and a blocking temperature of 340 K for the functionalized γ- Fe 2 O 3 nanoparticles.
Bibliographical noteFunding Information:
This work was partially supported by The National Council of Science, Technology and Technological Innovation (CONCYTEC/Cienciactiva-Peru). The authors wish to thank Dr. Alexandre Mello by allow access to the X- ray photoelectron spectroscopy equipment of the Multiuser Laboratory of Surfaces and Nanostructures at CBPF. M. Morales thanks Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for his fellowship, process number 305748/2015-7 . F.J. Litterst and E. Sadrollahi are grateful for partial support by DAAD.
- Le-Bail refinement
- Maghemite nanoparticles
- TEM microscopy