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Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.

Girgis E, Wahsh MM, Othman AG, Bandhu L, Rao K - Nanoscale Res Lett (2011)

Bottom Line: It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases.On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles.These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

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Affiliation: Solid State Physics Department, National Research Centre, 12311 Dokki, Giza, Egypt. egirgis@gmail.com.

ABSTRACT
The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

No MeSH data available.


Diffuse reflectance spectra of core/shell nanoparticles fired at 400°C (a), 600°C (b), and 800°C (c).
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Figure 6: Diffuse reflectance spectra of core/shell nanoparticles fired at 400°C (a), 600°C (b), and 800°C (c).

Mentions: Figure 6 shows the diffuse reflectance spectra of various cobalt ferrite, zinc ferrite, and cobalt zinc ferrite nanoparticles uncoated and coated with silica shell which were fired at 400°C (Figure 6a), 600°C (Figure 6b) and 800°C (Figure 6c). It is clear that zinc ferrite nanoparticles coated with silica shell exhibit the highest value of diffuse reflectance percentage compared with all core/shell ferrite samples. In addition, the diffuse reflectance percentage of zinc ferrite nanoparticles coated with silica increases by increasing the firing temperature from 400°C (37.4%) up to 800°C (44.64%). The diffuse reflectance percentage of uncoated zinc ferrite nanoparticles, fired at 400°C, 600°C and 800°C decreased compared with zinc ferrite nanoparticles coated with silica shell. This is attributed to the effect of silica shell, which enhances the optical properties of core/shell ferrite nanoparticles. On the other hand, cobalt ferrite nanoparticles show a very low diffuse reflectance compared with the other prepared nanoparticles (zinc ferrite and cobalt zinc ferrite nanoparticles). This is due to the effect of the change of color on the optical properties of the ferrite nanoparticles from black at CoFe2O4, to brown at Co0.5Zn0.5Fe2O4 and to orange at ZnFe2O4 by increasing the Zn2+ ions which substitute the Co2+ ions (Co1-xZnxFe2O4). In addition, the presence of the silica shell plays an important role in the optical properties enhancement of the prepared core/shell ferrite samples. When a beam of incident light impinges on the surface of these core/shell nanoparticles, only a small fraction is specularly reflected, while the remainder penetrates into the mass and undergoes scattering (multiple reflections, refractions, and diffraction in all directions) as well as wavelength-dependent absorption within the colored material (diffused rays will lose some wavelengths during their walk in the material, and will emerge colored). Part of this radiation ultimately leaves the mass in all directions and constitutes so-called diffusely reflected light [38].


Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.

Girgis E, Wahsh MM, Othman AG, Bandhu L, Rao K - Nanoscale Res Lett (2011)

Diffuse reflectance spectra of core/shell nanoparticles fired at 400°C (a), 600°C (b), and 800°C (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211881&req=5

Figure 6: Diffuse reflectance spectra of core/shell nanoparticles fired at 400°C (a), 600°C (b), and 800°C (c).
Mentions: Figure 6 shows the diffuse reflectance spectra of various cobalt ferrite, zinc ferrite, and cobalt zinc ferrite nanoparticles uncoated and coated with silica shell which were fired at 400°C (Figure 6a), 600°C (Figure 6b) and 800°C (Figure 6c). It is clear that zinc ferrite nanoparticles coated with silica shell exhibit the highest value of diffuse reflectance percentage compared with all core/shell ferrite samples. In addition, the diffuse reflectance percentage of zinc ferrite nanoparticles coated with silica increases by increasing the firing temperature from 400°C (37.4%) up to 800°C (44.64%). The diffuse reflectance percentage of uncoated zinc ferrite nanoparticles, fired at 400°C, 600°C and 800°C decreased compared with zinc ferrite nanoparticles coated with silica shell. This is attributed to the effect of silica shell, which enhances the optical properties of core/shell ferrite nanoparticles. On the other hand, cobalt ferrite nanoparticles show a very low diffuse reflectance compared with the other prepared nanoparticles (zinc ferrite and cobalt zinc ferrite nanoparticles). This is due to the effect of the change of color on the optical properties of the ferrite nanoparticles from black at CoFe2O4, to brown at Co0.5Zn0.5Fe2O4 and to orange at ZnFe2O4 by increasing the Zn2+ ions which substitute the Co2+ ions (Co1-xZnxFe2O4). In addition, the presence of the silica shell plays an important role in the optical properties enhancement of the prepared core/shell ferrite samples. When a beam of incident light impinges on the surface of these core/shell nanoparticles, only a small fraction is specularly reflected, while the remainder penetrates into the mass and undergoes scattering (multiple reflections, refractions, and diffraction in all directions) as well as wavelength-dependent absorption within the colored material (diffused rays will lose some wavelengths during their walk in the material, and will emerge colored). Part of this radiation ultimately leaves the mass in all directions and constitutes so-called diffusely reflected light [38].

Bottom Line: It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases.On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles.These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State Physics Department, National Research Centre, 12311 Dokki, Giza, Egypt. egirgis@gmail.com.

ABSTRACT
The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

No MeSH data available.