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Waleed E Mahmoud - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic ellipsometry of zn 1 x cu x o thin films based on a modified sol gel dip coating technique
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: Hibah A Alkhanbashi, W Shirbeeny, A A Alghamdi, Lyudmila M Bronstein, Waleed E MahmoudAbstract:Nanocrystalline Zn(1-x)Cu(x)O thin films (x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by sol-gel dip-coating technique on a quartz substrate. These films were annealed at 350°C for 2 h. The X-ray diffraction showed a hexagonal crystal structure with high intensity peak for the (002) Reflection Plane indicating preferential growth along the c-axis of the crystal lattice. The peak position related to the (002) peak was shifted as a result of the copper ion incorporation, confirming the interstitial substitution of the zinc ions by the copper ions. This interstitial substitution leads to a decrease of an average crystallite size and lattice constants and an increase of the micro-strain up to 2 at.% of the copper amount. The surface morphology was explored by scanning electron microscopy which confirmed the homogenous distribution of nanoparticles in the deposited films along the quartz substrates. The energy dispersion X-ray spectroscopy revealed absence of impurities in the as-deposited films. The high resolution electron microscopy and selected area electron diffraction depicted that the films have polycrystalline nature. The film thickness and optical constants of the Zn(1-x)Cu(x)O thin films were estimated by fitting the spectroscopic ellipsometric data (ψ and Δ) using three different models. The refractive index was fitted using harmonic oscillator model from which the oscillator and the dispersive energies were found. The dielectric constant, dielectric loss, energy loss functions were also determined.
R. Zivieri - One of the best experts on this subject based on the ideXlab platform.
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Symmetry properties and invariance of vortex-state linearized equations of motion in ferromagnetic dots -- Presentazione poster by R. Zivieri - Conferenza internazionale
IEEE Magnetics Italian Chapter & Magnetism Research Group University of Messina Italy, 2013Co-Authors: R. Zivieri, G. ConsoloAbstract:We prove some discrete space and time symmetries of linearized equations of motion in vortex-state ferromagnetic dots. The space symmetries are strictly related to the vortex-state configuration of the magnetization characterized by a chirality c= ±1 (counterclockwise or clockwise rotation of the magnetization) and a polarity p = ±1 (outward or inward core magnetization) and to its nature of axial vector. For a purely conservative dynamics, the linearized equation of motion in vortex-state ferromagnetic dots is written in the approximated form. First, we discuss the space symmetries. By placing the vortex parallel to the Reflection Plane (xy Plane) and by introducing the space Reflection operator σxy, the following symmetry transformation holds: σxy c= -c. The c switching leads to a change of sign of the in-Plane static magnetization component (M →-M) and of the in-Plane dynamic one, namely δmu→-δmu which leads to a change of sign of the corresponding dynamic effective field component δhu→-δhu. Moreover, there is also the switching δ mvC → −δ mvC of the core (C) component δ mvC = −δ mz cosθ with θ the polar angle. These transformations lead to the invariance of the equation of motion. By placing the vortex perpendicularly to the Reflection Plane (xy Plane), we get σxy p= - p. The p switching (vortex core switching) leads to δmu→-δmu and to δmz→-δmz leaving again the equation of motion invariant. A remarkable physical effect on spin dynamics is the interchange kv→-kv of the phases of azimuthal vortex modes characterized by the azimuthal number kv = ±1, ±2, .. obtained by using a Reflection operator xy σ in a quantum mechanical scheme We now discuss the time-reversal T symmetry, namely t →-t. Under this symmetry transformation both the static and dynamic quantities change sign, due to the reversal of angular moment of electrons, leaving Eq.(1) invariant like in the case of space symmetries. Within a quantum mechanical scheme, according to Wigner anti-unitary operator [2] the effect is equivalent to that of xy σ (kv→-kv) and leads to a change of the sense of rotation of azimuthal vortex modes including the gyrotropic. Instead, the dynamics of radial modes (kv = 0), is not affected by the T symmetry. [1] R. Zivieri and F. Nizzoli, Phys. Rev. B 75 (2005), 014411-1-5; ibidem Phys. Rev. B 74 (2006), 219901(E). [2] E.P. Wigner, Group theory and its application to the quantum mechanics, New York, Academic Press (1959), p.325
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Symmetries of vortex-state linearized equations of motion in ferromagnetic dots -- Presentazione poster by R. Zivieri -- Conferenza nazionale
Politecnico di Milano, 2013Co-Authors: R. ZivieriAbstract:We prove some discrete space and time symmetries of linearized equations of motion in vortex-state ferromagnetic dots in the absence of an external magnetic field. The space symmetries are strictly related to the vortex-state configuration of the magnetization characterized by a chirality c= ±1 (counterclockwise or clockwise rotation of the magnetization) and a polarity p = ±1 (outward or inward core magnetization) and to its nature of axial vector. For a purely conservative dynamics, the linearized equation of motion in vortex-state ferromagnetic dots is written in the approximated form [1]. The approximated linearized equation can be applied to ferromagnetic dots of any shape exhibiting a curling configuration and its solution expresses the deviation from the ground-state of vortex-state excitations. First, we discuss the space symmetries. By placing the vortex parallel to the Reflection Plane (xy Plane) the switching of the vortex chirality takes place. The chirality switching leads to a change of sign of the in-Plane static magnetization component and of the in-Plane dynamic one which, in turn, leads to a change of sign of the corresponding dynamic effective field component Moreover, there is also the switching of the core azimuthal component. These transformations lead to the invariance of the linearized equation of motion. By placing the vortex perpendicularly to the Reflection Plane (xy Plane), the switching of the vortex polarity takes place leading to a change of sign of both dynamical magnetization components leaving again the equation of motion invariant. A remarkable physical effect on spin dynamics is the interchange of the phases of azimuthal vortex modes characterized by the azimuthal number kv = ±1, ±2, .. obtained by using a Reflection operator in a quantum mechanical scheme. This corresponds to a change of the sense of rotation of azimuthal vortex modes including the gyrotropic. We also discuss the time-reversal T symmetry, namely t -t. Under this symmetry transformation both the static and dynamic quantities change sign, due to the reversal of angular momentum of electrons leaving the linearized equation of motion invariant like in the case of space symmetries. Within a quantum mechanical scheme, according to Wigner anti-unitary operator [2], the effect of time reversal is equivalent to that of the Reflection operator in a quantum mechanical scheme. The dynamics of radial modes (kv = 0) is not affected by the T symmetry. [1] R. Zivieri and F. Nizzoli, Phys. Rev. B 75 (2005), 014411-1-5; ibidem Phys. Rev. B 74 (2006), 219901(E). [2] E.P. Wigner, Group theory and its application to the quantum mechanics, New York, Academic Press (1959), p.325
Mohamad Hasnul Naim Abd Hamid - One of the best experts on this subject based on the ideXlab platform.
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green chemistry approach for the synthesis of zno nanopowders and their cytotoxic effects
Ceramics International, 2014Co-Authors: Majid Darroudi, Zahra Sabouri, Reza Kazemi Oskuee, Hadi Kargar, Ali Khorsand Zak, Mohamad Hasnul Naim Abd HamidAbstract:Abstract The use of natural polymers in the synthesis of nanomaterials can have a low cost and eco-friendly approach. In this work we would like to report the “ green chemistry ” synthesis of ZnO nanopowders (ZnO-NPs) using gelatin. Spherical ZnO-NPs were synthesized at different calcination temperatures and field emission scanning electron microscopy (FESEM) imaging showed the formation of most of nanopowders in nanoscale. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation at (101) Reflection Plane. In vitro cytotoxicity studies on neuro2A cells, a dose dependent toxicity with non-toxic effect of concentration below ~2 µg/mL was shown. The synthesis of ZnO-NPs in gelatinous media were found to be comparable to those obtained from the conventional reduction methods using hazardous polymers or surfactants which can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.
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sol gel synthesis characterization and neurotoxicity effect of zinc oxide nanoparticles using gum tragacanth
Ceramics International, 2013Co-Authors: Majid Darroudi, Zahra Sabouri, Reza Kazemi Oskuee, Hadi Kargar, Mohamad Hasnul Naim Abd HamidAbstract:Abstract The use of plant extract in the synthesis of nanomaterials can be a cost effective and eco-friendly approach. In this work we report the “ green” and biosynthesis of zinc oxide nanoparticles (ZnO-NPs) using gum tragacanth . Spherical ZnO-NPs were synthesized at different calcination temperatures. Transmission electron microscopy (TEM) imaging showed the formation most of nanoparticles in the size range of below 50 nm. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation in (101) Reflection Plane. In vitro cytotoxicity studies on neuro2A cells showed a dose dependent toxicity with non-toxic effect of concentration below 2 µg/mL. The synthesized ZnO-NPs using gum tragacanth were found to be comparable to those obtained from conventional reduction methods using hazardous polymers or surfactants and this method can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.
Lyudmila M Bronstein - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic ellipsometry of zn 1 x cu x o thin films based on a modified sol gel dip coating technique
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: Hibah A Alkhanbashi, W Shirbeeny, A A Alghamdi, Lyudmila M Bronstein, Waleed E MahmoudAbstract:Nanocrystalline Zn(1-x)Cu(x)O thin films (x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by sol-gel dip-coating technique on a quartz substrate. These films were annealed at 350°C for 2 h. The X-ray diffraction showed a hexagonal crystal structure with high intensity peak for the (002) Reflection Plane indicating preferential growth along the c-axis of the crystal lattice. The peak position related to the (002) peak was shifted as a result of the copper ion incorporation, confirming the interstitial substitution of the zinc ions by the copper ions. This interstitial substitution leads to a decrease of an average crystallite size and lattice constants and an increase of the micro-strain up to 2 at.% of the copper amount. The surface morphology was explored by scanning electron microscopy which confirmed the homogenous distribution of nanoparticles in the deposited films along the quartz substrates. The energy dispersion X-ray spectroscopy revealed absence of impurities in the as-deposited films. The high resolution electron microscopy and selected area electron diffraction depicted that the films have polycrystalline nature. The film thickness and optical constants of the Zn(1-x)Cu(x)O thin films were estimated by fitting the spectroscopic ellipsometric data (ψ and Δ) using three different models. The refractive index was fitted using harmonic oscillator model from which the oscillator and the dispersive energies were found. The dielectric constant, dielectric loss, energy loss functions were also determined.
Majid Darroudi - One of the best experts on this subject based on the ideXlab platform.
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green chemistry approach for the synthesis of zno nanopowders and their cytotoxic effects
Ceramics International, 2014Co-Authors: Majid Darroudi, Zahra Sabouri, Reza Kazemi Oskuee, Hadi Kargar, Ali Khorsand Zak, Mohamad Hasnul Naim Abd HamidAbstract:Abstract The use of natural polymers in the synthesis of nanomaterials can have a low cost and eco-friendly approach. In this work we would like to report the “ green chemistry ” synthesis of ZnO nanopowders (ZnO-NPs) using gelatin. Spherical ZnO-NPs were synthesized at different calcination temperatures and field emission scanning electron microscopy (FESEM) imaging showed the formation of most of nanopowders in nanoscale. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation at (101) Reflection Plane. In vitro cytotoxicity studies on neuro2A cells, a dose dependent toxicity with non-toxic effect of concentration below ~2 µg/mL was shown. The synthesis of ZnO-NPs in gelatinous media were found to be comparable to those obtained from the conventional reduction methods using hazardous polymers or surfactants which can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.
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sol gel synthesis characterization and neurotoxicity effect of zinc oxide nanoparticles using gum tragacanth
Ceramics International, 2013Co-Authors: Majid Darroudi, Zahra Sabouri, Reza Kazemi Oskuee, Hadi Kargar, Mohamad Hasnul Naim Abd HamidAbstract:Abstract The use of plant extract in the synthesis of nanomaterials can be a cost effective and eco-friendly approach. In this work we report the “ green” and biosynthesis of zinc oxide nanoparticles (ZnO-NPs) using gum tragacanth . Spherical ZnO-NPs were synthesized at different calcination temperatures. Transmission electron microscopy (TEM) imaging showed the formation most of nanoparticles in the size range of below 50 nm. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation in (101) Reflection Plane. In vitro cytotoxicity studies on neuro2A cells showed a dose dependent toxicity with non-toxic effect of concentration below 2 µg/mL. The synthesized ZnO-NPs using gum tragacanth were found to be comparable to those obtained from conventional reduction methods using hazardous polymers or surfactants and this method can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.