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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.

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.


XRD patterns of core/shell CoFe2O4/SiO2 (a), Co0.5Zn0.5Fe2O4/SiO2 (b), and ZnFe2O4/SiO2 (c) nanoparticles.
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Figure 1: XRD patterns of core/shell CoFe2O4/SiO2 (a), Co0.5Zn0.5Fe2O4/SiO2 (b), and ZnFe2O4/SiO2 (c) nanoparticles.

Mentions: Figure 1a, b, c shows the X-ray diffraction patterns of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles, in which x = 0, 0.5, and 1, respectively. All the strong peaks appeared at 2θ = 18.4°, 30.084°, 35.437°, 37.057°, 43.058°, 53.445°, 56.973°, 62.585°, 70.78°, 74.009°, and 75.00° are indexed to the crystal plane of spinel ferrite (Co1-xZnxFe2O4) structure (111), (220), (311), (222), (400), (422), (511), (440), (620), (533), and (622), respectively. In addition, the intensities of the peaks are found to increase by increasing the firing temperature due to the increase of the crystalline phase. From Figure 1a, b, it was observed that the X-ray diffraction patterns (XRD) of Co0.5Zn0.5Fe2O4 nanoparticles having the same crystal plane of CoFe2O4 nanoparticles which confirms the formation of the good spinel structure. In addition, no secondary phase was detected in XRD patterns which ensure the purity of the Co0.5Zn0.5Fe2O4 nanoparticles. The average crystallite size of Co1-xZnxFe2O4/SiO2 nanoparticles were estimated using the Scherrer's formula; D = 0.9λ/(FWHM × cos θ), where D is the crystallite size; FWHM is the observed full width at half maximum; θ is the Bragg angle, and λ is the wavelength of the X- ray radiation (λ = 1.54058 Å). In addition, a broad peak at 2θ approximately 22-25° has been detected in the samples coated with silica shell and fired at 400°C for 2 h as shown in Figure 1a. This broad peak is due to the presence of the amorphous silica. By increasing the firing temperature, amorphous silica starts to disappear and only the diffraction peaks of spinel ferrite Co1-xZnxFe2O4 phase were detected due to the formation of good core/shell structure. Figure 1c shows the XRD pattern of the zinc ferrite/silica nanoparticles (ZFS) fired at 800°C. Similar phases have been observed as mentioned above except for the presence of three weak diffraction peaks at 2θ = 33.194°, 48.94°, and 54.06° corresponding to (410), (333), and (603) crystal planes of rhombohedral zinc silicate phase. The latter phase arises because of solid state reaction of ZnO resulting from small dissociation of ZnFe2O4 core at high temperature (800°C) with SiO2 shell forming Zn2SiO4 phase.


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)

XRD patterns of core/shell CoFe2O4/SiO2 (a), Co0.5Zn0.5Fe2O4/SiO2 (b), and ZnFe2O4/SiO2 (c) nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 1: XRD patterns of core/shell CoFe2O4/SiO2 (a), Co0.5Zn0.5Fe2O4/SiO2 (b), and ZnFe2O4/SiO2 (c) nanoparticles.
Mentions: Figure 1a, b, c shows the X-ray diffraction patterns of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles, in which x = 0, 0.5, and 1, respectively. All the strong peaks appeared at 2θ = 18.4°, 30.084°, 35.437°, 37.057°, 43.058°, 53.445°, 56.973°, 62.585°, 70.78°, 74.009°, and 75.00° are indexed to the crystal plane of spinel ferrite (Co1-xZnxFe2O4) structure (111), (220), (311), (222), (400), (422), (511), (440), (620), (533), and (622), respectively. In addition, the intensities of the peaks are found to increase by increasing the firing temperature due to the increase of the crystalline phase. From Figure 1a, b, it was observed that the X-ray diffraction patterns (XRD) of Co0.5Zn0.5Fe2O4 nanoparticles having the same crystal plane of CoFe2O4 nanoparticles which confirms the formation of the good spinel structure. In addition, no secondary phase was detected in XRD patterns which ensure the purity of the Co0.5Zn0.5Fe2O4 nanoparticles. The average crystallite size of Co1-xZnxFe2O4/SiO2 nanoparticles were estimated using the Scherrer's formula; D = 0.9λ/(FWHM × cos θ), where D is the crystallite size; FWHM is the observed full width at half maximum; θ is the Bragg angle, and λ is the wavelength of the X- ray radiation (λ = 1.54058 Å). In addition, a broad peak at 2θ approximately 22-25° has been detected in the samples coated with silica shell and fired at 400°C for 2 h as shown in Figure 1a. This broad peak is due to the presence of the amorphous silica. By increasing the firing temperature, amorphous silica starts to disappear and only the diffraction peaks of spinel ferrite Co1-xZnxFe2O4 phase were detected due to the formation of good core/shell structure. Figure 1c shows the XRD pattern of the zinc ferrite/silica nanoparticles (ZFS) fired at 800°C. Similar phases have been observed as mentioned above except for the presence of three weak diffraction peaks at 2θ = 33.194°, 48.94°, and 54.06° corresponding to (410), (333), and (603) crystal planes of rhombohedral zinc silicate phase. The latter phase arises because of solid state reaction of ZnO resulting from small dissociation of ZnFe2O4 core at high temperature (800°C) with SiO2 shell forming Zn2SiO4 phase.

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.