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Tunable magnetic nanowires for biomedical and harsh environment applications.

Ivanov YP, Alfadhel A, Alnassar M, Perez JE, Vazquez M, Chuvilin A, Kosel J - Sci Rep (2016)

Bottom Line: The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations.This property renders these core-shell nanowires attractive materials for application to harsh environments.A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

View Article: PubMed Central - PubMed

Affiliation: Computer, Electrical and Mathematical Sciences and Engineering Division (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.

ABSTRACT
We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

No MeSH data available.


(a) HR-TEM cross-sectional image of a single-crystal core-shell Fe nanowire (after 72 hours of annealing of a single-crystal Fe nanowire). EELS spectra of the cross-section of an Fe nanowire annealed for 24 hours: (b) the single-crystalline portion and (c) the polycrystalline portion (the end of the nanowire, where the growth started from). (d) A spectrum obtained by EELS from core and shell regions. (e) White-line ratios of the Fe L23 edge for the core, shell and reference samples of different iron oxides measured using the same techniques.
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f6: (a) HR-TEM cross-sectional image of a single-crystal core-shell Fe nanowire (after 72 hours of annealing of a single-crystal Fe nanowire). EELS spectra of the cross-section of an Fe nanowire annealed for 24 hours: (b) the single-crystalline portion and (c) the polycrystalline portion (the end of the nanowire, where the growth started from). (d) A spectrum obtained by EELS from core and shell regions. (e) White-line ratios of the Fe L23 edge for the core, shell and reference samples of different iron oxides measured using the same techniques.

Mentions: Figure 6a shows a high-resolution TEM (HRTEM) cross-sectional image of a single-crystal core-shell Fe nanowire after 72 hours of annealing. Agreement of the SAED patterns with those of the reference Fe3O4 does not necessarily indicate that the phase of the oxide shell corresponds to magnetite. This is because the electron diffraction ring patterns of Fe3O4 and γ-Fe2O3 are very similar36. Thus, the oxide shell can be either Fe3O4 or γ-Fe2O3 or a mixture of both. Spectra obtained by electron energy loss spectroscopy (EELS) for a specific atomic species are influenced by both the coordination chemistry and the valence state of the atomic species being measured37. Figure 6b shows the EELS map of the cross-section of a core-shell NW (single-crystalline Fe NW after 24 hours of annealing) prepared by focused ion beam protocol. Two distinguished regions are clearly visible namely, the Fe core and the surrounding Fe-O shell. In contrast, the EELS map of the cross-section of a polycrystalline section (at the end of the NW, where the growth started from) shown in Fig. 6c denotes a completely oxidized Fe-O state. The blue circle around the NW arises from the Cr edge, caused by remnants of the chrome solution used to release the NWs from the AOT (see the Methods section).


Tunable magnetic nanowires for biomedical and harsh environment applications.

Ivanov YP, Alfadhel A, Alnassar M, Perez JE, Vazquez M, Chuvilin A, Kosel J - Sci Rep (2016)

(a) HR-TEM cross-sectional image of a single-crystal core-shell Fe nanowire (after 72 hours of annealing of a single-crystal Fe nanowire). EELS spectra of the cross-section of an Fe nanowire annealed for 24 hours: (b) the single-crystalline portion and (c) the polycrystalline portion (the end of the nanowire, where the growth started from). (d) A spectrum obtained by EELS from core and shell regions. (e) White-line ratios of the Fe L23 edge for the core, shell and reference samples of different iron oxides measured using the same techniques.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4829833&req=5

f6: (a) HR-TEM cross-sectional image of a single-crystal core-shell Fe nanowire (after 72 hours of annealing of a single-crystal Fe nanowire). EELS spectra of the cross-section of an Fe nanowire annealed for 24 hours: (b) the single-crystalline portion and (c) the polycrystalline portion (the end of the nanowire, where the growth started from). (d) A spectrum obtained by EELS from core and shell regions. (e) White-line ratios of the Fe L23 edge for the core, shell and reference samples of different iron oxides measured using the same techniques.
Mentions: Figure 6a shows a high-resolution TEM (HRTEM) cross-sectional image of a single-crystal core-shell Fe nanowire after 72 hours of annealing. Agreement of the SAED patterns with those of the reference Fe3O4 does not necessarily indicate that the phase of the oxide shell corresponds to magnetite. This is because the electron diffraction ring patterns of Fe3O4 and γ-Fe2O3 are very similar36. Thus, the oxide shell can be either Fe3O4 or γ-Fe2O3 or a mixture of both. Spectra obtained by electron energy loss spectroscopy (EELS) for a specific atomic species are influenced by both the coordination chemistry and the valence state of the atomic species being measured37. Figure 6b shows the EELS map of the cross-section of a core-shell NW (single-crystalline Fe NW after 24 hours of annealing) prepared by focused ion beam protocol. Two distinguished regions are clearly visible namely, the Fe core and the surrounding Fe-O shell. In contrast, the EELS map of the cross-section of a polycrystalline section (at the end of the NW, where the growth started from) shown in Fig. 6c denotes a completely oxidized Fe-O state. The blue circle around the NW arises from the Cr edge, caused by remnants of the chrome solution used to release the NWs from the AOT (see the Methods section).

Bottom Line: The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations.This property renders these core-shell nanowires attractive materials for application to harsh environments.A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

View Article: PubMed Central - PubMed

Affiliation: Computer, Electrical and Mathematical Sciences and Engineering Division (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.

ABSTRACT
We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

No MeSH data available.