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Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O 4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals.

Al Khabouri S, Al Harthi S, Maekawa T, Nagaoka Y, Elzain ME, Al Hinai A, Al-Rawas AD, Gismelseed AM, Yousif AA - Nanoscale Res Lett (2015)

Bottom Line: The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes.Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed.Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Sultan Qaboos University, Muscat, PC 123, Sultanate of Oman, p024168@student.squ.edu.om.

ABSTRACT
We report investigation on properties of multiwall carbon nanotubes (mCNTs) containing Ni residuals before and after encapsulation of zinc ferrite nanoparticles. The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes. Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed. As a result of the encapsulation, enhancement in the σ bands density of state and coating of the zinc ferrite nanoparticles by the internal layers of the CNTs in the direction along the tube axis is observed. Furthermore, Ni impurities inside the tubes are attracted to the encapsulated zinc ferrite nanoparticles, suggesting the possibility of using these particles as purifying agents for CNTs upon being synthesized using magnetic catalyst particles. Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization. Furthermore, it is demonstrated that encapsulated zinc ferrite nanoparticles in mCNTs resulted in two interacting sub-systems featured by distinct blocking temperatures and enhanced magnetic properties; i.e., large coercivity of 501 Oe and saturation magnetization of 2.5 emu/g at 4 K.

No MeSH data available.


Related in: MedlinePlus

The overall XPS spectra of mCNTs and few layers of graphene. Deconvolution of the XPS spectrum of the C1s carbon level of the mCNTs (inset)
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Fig2: The overall XPS spectra of mCNTs and few layers of graphene. Deconvolution of the XPS spectrum of the C1s carbon level of the mCNTs (inset)

Mentions: Figure 2 shows the XPS survey spectra recorded for mCNTs and graphene. The commonly observed π-π* transition is positioned in the mCNTs at 290.5 eV for both samples. Oxygen and nickel are not detected in the mCNTs. This could be due to small oxygen and Ni concentrations below XPS detection limit (i.e., 0.1 %). C 1 s core level excitations of mCNTs are shown as an inset of Fig. 2. The simulation using CASA XPS Software suggests peaks positioned at 284.3 and 285.1 eV corresponding to sp2 and sp3 hybridized states, respectively. Quantification of sp2/sp3 ratio reveals the dominance of sp2 hybridization (i.e., sp2/sp3 = 2.04, where sp2 = 67 % and sp3 = 33 %), which is characteristic of a two-dimensional sheet of sp2 bonded carbon atoms [15]. The peak at 284.5 eV could be attributed to some carbon impurities left behind after sample preparation [16]. The D parameter gives an indication of the relative amounts of sp2 and sp3 carbon. The D parameter is defined as the separation in energy between the most positive and most negative excursions obtained from the first derivative Auger transition C KVV spectrum. In the spectrum of the mCNTs sample, the value of this parameter is 19.1 eV which agrees well with the value obtained for mCNTs obtained by Bolotov et al. [17]. The presence of sp3 carbon atoms may be associated with the defects caused by the presence of Ni impurities or the presence of a layer of turbostratic carbon [18, 19].Fig. 2


Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O 4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals.

Al Khabouri S, Al Harthi S, Maekawa T, Nagaoka Y, Elzain ME, Al Hinai A, Al-Rawas AD, Gismelseed AM, Yousif AA - Nanoscale Res Lett (2015)

The overall XPS spectra of mCNTs and few layers of graphene. Deconvolution of the XPS spectrum of the C1s carbon level of the mCNTs (inset)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4478189&req=5

Fig2: The overall XPS spectra of mCNTs and few layers of graphene. Deconvolution of the XPS spectrum of the C1s carbon level of the mCNTs (inset)
Mentions: Figure 2 shows the XPS survey spectra recorded for mCNTs and graphene. The commonly observed π-π* transition is positioned in the mCNTs at 290.5 eV for both samples. Oxygen and nickel are not detected in the mCNTs. This could be due to small oxygen and Ni concentrations below XPS detection limit (i.e., 0.1 %). C 1 s core level excitations of mCNTs are shown as an inset of Fig. 2. The simulation using CASA XPS Software suggests peaks positioned at 284.3 and 285.1 eV corresponding to sp2 and sp3 hybridized states, respectively. Quantification of sp2/sp3 ratio reveals the dominance of sp2 hybridization (i.e., sp2/sp3 = 2.04, where sp2 = 67 % and sp3 = 33 %), which is characteristic of a two-dimensional sheet of sp2 bonded carbon atoms [15]. The peak at 284.5 eV could be attributed to some carbon impurities left behind after sample preparation [16]. The D parameter gives an indication of the relative amounts of sp2 and sp3 carbon. The D parameter is defined as the separation in energy between the most positive and most negative excursions obtained from the first derivative Auger transition C KVV spectrum. In the spectrum of the mCNTs sample, the value of this parameter is 19.1 eV which agrees well with the value obtained for mCNTs obtained by Bolotov et al. [17]. The presence of sp3 carbon atoms may be associated with the defects caused by the presence of Ni impurities or the presence of a layer of turbostratic carbon [18, 19].Fig. 2

Bottom Line: The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes.Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed.Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Sultan Qaboos University, Muscat, PC 123, Sultanate of Oman, p024168@student.squ.edu.om.

ABSTRACT
We report investigation on properties of multiwall carbon nanotubes (mCNTs) containing Ni residuals before and after encapsulation of zinc ferrite nanoparticles. The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes. Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed. As a result of the encapsulation, enhancement in the σ bands density of state and coating of the zinc ferrite nanoparticles by the internal layers of the CNTs in the direction along the tube axis is observed. Furthermore, Ni impurities inside the tubes are attracted to the encapsulated zinc ferrite nanoparticles, suggesting the possibility of using these particles as purifying agents for CNTs upon being synthesized using magnetic catalyst particles. Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization. Furthermore, it is demonstrated that encapsulated zinc ferrite nanoparticles in mCNTs resulted in two interacting sub-systems featured by distinct blocking temperatures and enhanced magnetic properties; i.e., large coercivity of 501 Oe and saturation magnetization of 2.5 emu/g at 4 K.

No MeSH data available.


Related in: MedlinePlus