Fernando Pelegrini - Academia.edu (original) (raw)

Papers by Fernando Pelegrini

Research paper thumbnail of Magnetic resonance as a technique to study particle-to-particle interactions in magnetic fluids

Magnetic resonance is presented as a useful technique to study particle-to-particle interactions ... more Magnetic resonance is presented as a useful technique to study particle-to-particle interactions in magnetic fluids. The characteristic feature of all experiments the authors have done is a remarkable change in the resonance linewidth. A theoretical model that includes magnetic and electrical interactions between adjacent particles is presented. Experimental results will be presented and discussed in terms of this model.

Research paper thumbnail of Paramagnetic behavior at room temperature of Zn1−xMnxTe nanocrystals grown in a phosphate glass matrix by the fusion method

Journal of Alloys and Compounds, 2015

This work reports on the synthesis and characterization of Zn 1-x Mn x Te nanocrystals (NCs) with... more This work reports on the synthesis and characterization of Zn 1-x Mn x Te nanocrystals (NCs) with Mn doping concentration x varying from 0.000 to 0.800. Physical properties of samples were studied by transmission electron microscopy, magnetic force

Research paper thumbnail of Surface and exchange anisotropy fields in MnFe2O4 nanoparticles: Size and temperature effects

Journal of Applied Physics, 1999

Angular measurements of magnetic resonance are used to investigate the surface anisotropy field a... more Angular measurements of magnetic resonance are used to investigate the surface anisotropy field as well as the exchange anisotropy field in spherical MnFe2O4 magnetic nanoparticles as a function of temperature and particle diameter (D). The resonance field is a combination of angular dependent and angular independent fields, both affected by the surface anisotropy field, which in turn follows a D−α power law, with α very close to unity. The angular dependent component probes the surface anisotropy field while the angular independent component probes the exchange anisotropy field. In the temperature range from 100 to 250 K a negative surface anisotropy field is found, which increases as the particle size is reduced, indicating a radial orientation of the spins at the MnFe2O4 nanoparticle surface.

Research paper thumbnail of Light microscopy and magnetic resonance characterization of a DMSA-coated magnetic fluid in mice

IEEE Transactions on Magnetics, 2002

Research paper thumbnail of Morphology in semimagnetic Pb1−xMnxSe nanocrystals: Thermal annealing effects

Applied Physics Letters, 2009

Samples of Pb1−xMnxSe nanocrystals were synthesized by fusion method and characterized by optical... more Samples of Pb1−xMnxSe nanocrystals were synthesized by fusion method and characterized by optical absorption, atomic force microscopy, x-ray diffraction, and electron paramagnetic resonance (EPR) techniques. Effects of Mn2+ ion incorporation into PbSe nanocrystals are manifested by well resolved optical spectra for different concentrations of Mn. The EPR spectra of as grown and thermal annealed Pb1−xMnxSe samples show that the magnetic properties of these Mn-doped nanocrystals can be tuned by thermal processes using different annealing times.

Research paper thumbnail of Evidence of Cd1−xMnxS nanocrystal growth in a glass matrix by the fusion method

Applied Physics Letters, 2008

In this work, CdS nanocrystals (NCs) doped with Mn were synthesized in a glass matrix by fusion. ... more In this work, CdS nanocrystals (NCs) doped with Mn were synthesized in a glass matrix by fusion. The as-grown Cd1−xMnxS NCs were investigated by optical absorption, atomic force microscopy, and electron paramagnetic resonance (EPR). The incorporation of Mn2+ ions in CdS NCs was confirmed by an absorption transition blueshift with increasing Mn concentration x. EPR spectra demonstrated the existence of two distinct Mn2+ ion locations: one incorporated in the core and the other near the surface of the Cd1−xMnxS NCs. The hyperfine interaction constants used to simulate the EPR spectra were A=7.6 and 8.2 mT, respectively. The synthesis of high quality Cd1−xMnxS NCs may allow the control of optical and magnetic properties.

Research paper thumbnail of Ferromagnetic resonance in GdAl2crystals doped with anisotropic rare-earth ions

Journal of Physics C: Solid State Physics, 1984

Ferromagnetic resonance measurements of the magnetic anisotropy and resonance linewidth are repor... more Ferromagnetic resonance measurements of the magnetic anisotropy and resonance linewidth are reported for single-crystal specimens of the cubic Laves-phase intermetallic compound GdAl2 and for RxGd1-xAl2 where R is a heavy rare-earth ion. The doping levels of the samples were: for R=Tb, x=0.0025, 0.01, 0.02, 0.05; for R=Dy, x=0.02; for R=Ho, x=0.02; for R=Er, x=0.01, 0.03. Microwave frequencies close to 9.3,

Research paper thumbnail of Magnetic surface anisotropy and ferromagnetic resonance in GdAl 2 crystals

Journal of Physics F: Metal Physics, 1984

Ferromagnetic resonance observed in a GdAl2 crystal consists of a bulk mode and a surface-induced... more Ferromagnetic resonance observed in a GdAl2 crystal consists of a bulk mode and a surface-induced mode. At 80K the former predominates but, as the temperature is reduced, the relative intensity of this mode decreases and at 20K only the surface-induced mode is observed. At the higher temperature the anisotropy of the field for ferromagnetic resonance is as predicted from the statically measured magnetocrystalline anisotropy, but at 20K this is not so, because the resonance of the surface-induced mode is shifted by magnetic surface anisotropy. Three surface anisotropy constants are needed to describe this effect; their values are estimated as Ku=0.02C, K'u=-0.009C, Kn=0.33C. The value adopted for C=2Ms(2 pi A)1/2 is 1.47 erg cm-2.

Research paper thumbnail of Identification and valuation of paramagnetic radicals in natural dolomites as an indicator of geological events

Physics and Chemistry of Minerals, 2003

Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron ... more Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron paramagnetic resonance (EPR) spectroscopy. The complex spectra in the g ¼ 2.0 region is composed of Mn 2+ lines and signals due to crystallization and radiationinduced defects. Measurements in microwave frequencies of 9.5 GHz (X-band) and 35 GHz (Q-band), and thermal and/or radiation treatments allowed identification of seven paramagnetic radicals in the g ¼ 2.0 region: (1) isotropic organic radical; (2) axial SO À 2 ; (3) axial PO 0 2 or PO 2À 2 ; (4) isotropic CO À 2 ; (5) axial CO À 2 ; (6) axial CO 3À 3 ; (7) isotropic unknown line. The use of these paramagnetic centres as indicators of geological events is discussed.

Research paper thumbnail of Biodistribution and biocompatibility investigation in magnetoliposome treated mice

Spectroscopy, 2004

Magnetoliposomes (ML's) may be successfully applied for several purposes. A dimyristoylphosph... more Magnetoliposomes (ML's) may be successfully applied for several purposes. A dimyristoylphosphatidyl‒choline‒based ML (ML‒2) sample was developed as a precursor of more complex thermal cancer therapy systems. The present study reports on morphology and magnetic resonance (MR) investigations carried out with the magnetite‒based ML‒2 sample. For the experiments, adult female Swiss mice were endovenously treated with a bolus dose of 100 µl of ML‒2. Morphology and room‒temperature MR studies (X‒band experiments) were performed in several organs collected from 1 hour to 28 days after ML administration. Histological data showed magnetic nanoparticle (MNP) clusters up to the 28th day in the liver and spleen tissues. In spite of the presence of MNP clusters, no morphological alterations were observed, supporting the biocompatibility of the ML‒2. MR signal was detected only in the liver and spleen tissues and showed that the MNP's concentration was not altered from 48 hours to 28 days...

Research paper thumbnail of Investigation of the Brownian relaxation and hydrodynamic radius in magnetic nanoparticles

Solid State Communications, 1997

Magnetic resonance is used to estimate the Brownian relaxation time and hydrodynamic radius of Mn... more Magnetic resonance is used to estimate the Brownian relaxation time and hydrodynamic radius of MnFezOd ferrite nanoparticles in suspension in a magnetic fluid. By measuring the resonance linewidth broadening as a function of the particle-particle distance and as a function of the temperature, relaxation time and hydrodynamic radius respectively of the order of 4.8~s and 11.7mn were estimated. The relaxation time falls within the expected range and the hydrodynamic radius is found to be 2.2 times the mean value of the particle radius (54nm), in excellent agreement with the literature.

Research paper thumbnail of Synthesis and magnetic characterization of Pb1−xMnxS nanocrystals in glass matrix

Journal of Physics D: Applied Physics, 2008

The synthesis of manganese-doped PbS (Pb1-xMnxS) nanocrystal (NC) dots within a borosilicate glas... more The synthesis of manganese-doped PbS (Pb1-xMnxS) nanocrystal (NC) dots within a borosilicate glass matrix has been investigated by atomic force microscopy, electron paramagnetic resonance and magnetic measurements. The fusion method was employed in the preparation of the magnetic semiconductor NC dots whereas the measurements performed showed changes in the physical properties of the manganese-doped dots as a result of the

Research paper thumbnail of In vitro toxicity of magnetic fluids evaluated for macrophage cell lines

Journal of Magnetism and Magnetic Materials, 2002

ABSTRACT To determine macrophage cell lines, the analysis of in vitro toxicity of magnetic fluids... more ABSTRACT To determine macrophage cell lines, the analysis of in vitro toxicity of magnetic fluids was discussed. Ferrofluid-dimercaptosuccinic acid (FFDMSA) and dextran-coated ferrofluid (FFDX) were used to determine the viability of the cells. The color of ferrofluids adsorbed or internalized inside the cells impaired the use of metabolic tests based on the production of a chromogen. It was found that the FFDMSA showed a dramatic effect on cell growth whereas FFDX showed a limited toxicity even at high concentration , as compared to the FFDMSA.

Research paper thumbnail of Synthesis of manganese ferrite nanoparticles in macroporous styrene-divinylbenzene copolymer

Journal of Magnetism and Magnetic Materials, 2004

Preparation of manganese ferrite ðMnFe 2 O 4 Þ in a polymer template is described in this work. T... more Preparation of manganese ferrite ðMnFe 2 O 4 Þ in a polymer template is described in this work. The ferrite-based samples were prepared in situ by two routes: (I) alkaline oxidation of Fe 3þ and Mn 2þ ions and (II) alkaline oxidation of Fe 2þ and Mn 2þ ions. The nanocomposites were characterized using chemical analysis, X-ray diffraction, M. ossbauer spectroscopy and magnetic resonance. It was found that route-I produced smaller particles than route-II. This effect can be attributed to the oxidation state of iron ions and their interaction with the polymeric template.

Research paper thumbnail of Ferromagnetic resonance of ferrite ferrofluids at high microwave power levels

Journal of Magnetism and Magnetic Materials, 2004

ABSTRACT

Research paper thumbnail of Use of magnetic resonance to study biodistribution of dextran-coated magnetic fluid intravenously administered in mice

Journal of Magnetism and Magnetic Materials, 2002

... LM Lacava a , ZGM Lacava Corresponding Author Contact Information , E-mail The Corresponding ... more ... LM Lacava a , ZGM Lacava Corresponding Author Contact Information , E-mail The Corresponding Author , a , RB Azevedo a , SB Chaves a , VAP Garcia a , O. Silva b , F. Pelegrini b , N. Buske c , C. Gansau c , MF Da Silva d and PC Morais d. a Dept. ...

Research paper thumbnail of Magnetic resonance investigation of monodisperse oleoylsarcosine-coated magnetic fluid

Journal of Magnetism and Magnetic Materials, 2005

Magnetic resonance experiments were used to investigate the occurrence of particle arrays induced... more Magnetic resonance experiments were used to investigate the occurrence of particle arrays induced by the application of a small steady field (50 G) during the frozen procedure. In order to skip from the size-dependent effects the sample was filtered to a very narrow distribution of particle sizes. Three well-defined components were chosen to fit the envelope resonance line. Analyses of the resonance field versus temperature of each component were used as a support for the occurrence of dimers and tetramers as the dominant magnetic arrays.

Research paper thumbnail of Ferromagnetic resonance line of ferrite ferrofluids at high microwave power

Journal of Magnetism and Magnetic Materials, 2005

... References. [1] P. Kabos, CE Patton, G. Wiese, AD Sullins, ES Wright and L. Chen. J. Appl. Ph... more ... References. [1] P. Kabos, CE Patton, G. Wiese, AD Sullins, ES Wright and L. Chen. J. Appl. Phys., 80 (1996), p. 3962. ... [9] SV Vonsovskii (Ed.), Ferromagnetic Resonance, Pergamon, Oxford, 1966, p. 274.. [10] I. Hrianca, I. Malaescu, F. Claici and CN Marin. J. Magn. Magn. ...

Research paper thumbnail of Long-Term Biodistribution and Biocompatibility Investigation of Dextran-Coated Magnetite Nanoparticle Using Mice as the Animal Model

Journal of Biomedical Nanotechnology, 2012

Magnetic resonance is used to investigate biodistribution aspects of dextran-coated magnetite nan... more Magnetic resonance is used to investigate biodistribution aspects of dextran-coated magnetite nanoparticles (9.4 nm core diameter) in both liver and spleen from 5 minutes up to 6 months after intravenous administration of a magnetic fluid sample in female Swiss mice. Using magnetic resonance data important parameters such as the absorption half-life (t 1/2 = 12 +/- 2 min in the liver and t 1/2 = 11 +/- 2 min in the spleen), the peak time (1.7 +/- 0.2 h in the liver and 1.9 +/- 0.2 h in the spleen), and the disposition half-life of the dextran-coated magnetite nanoparticles in mice organs (t 1/2 = 70 +/- 10 h in the liver and t 1/2 = 32 +/- 7 h in the spleen) were assessed. In addition, light and electron microscopy showed several aspects that may be related to the iron metabolism. Microscopic analysis also revealed that although magnetite nanoparticles or iron released from them are retained in the organism for a long period of time, no morphologic alteration is induced by the intravenous administration of the magnetic fluid sample, evidencing its biocompatibility. The used tests may represent an adequate methodology for nanotoxicology evaluation.

Research paper thumbnail of Control of magnetic behavior by Pb1-xMnxS nanocrystals in a glass matrix

Journal of Applied Physics, 2012

ABSTRACT Diluted magnetic semiconductor nanocrystals, Pb1-xMnxS (x = 0.003, 0.005, and 0.010), of... more ABSTRACT Diluted magnetic semiconductor nanocrystals, Pb1-xMnxS (x = 0.003, 0.005, and 0.010), of approximately 6 nm were successfully grown in a glass matrix by a combination of fusion and thermal annealing. X-ray diffraction measurements reveal that the as-produced nanocrystals (NC), of group IV–VI, are single-phase, nanosized and crystallized in the rock salt structure with replacement of Pb2+-ions by Mn2+-ions. Magnetic force microscopy images also confirmed the high quality of the Pb1-xMnxS NC samples, showing a uniform distribution of total magnetic moments in the nanocrystals. The observation of characteristic hyperfine structures from electron paramagnetic resonance measurements provided evidence for Mn2+ incorporation within the PbS dot structure. Moreover, low temperature magnetization and susceptibility data showed that most of the magnetic ions hosted by the nanocomposite samples are in a paramagnetic state.

Research paper thumbnail of Magnetic resonance as a technique to study particle-to-particle interactions in magnetic fluids

Magnetic resonance is presented as a useful technique to study particle-to-particle interactions ... more Magnetic resonance is presented as a useful technique to study particle-to-particle interactions in magnetic fluids. The characteristic feature of all experiments the authors have done is a remarkable change in the resonance linewidth. A theoretical model that includes magnetic and electrical interactions between adjacent particles is presented. Experimental results will be presented and discussed in terms of this model.

Research paper thumbnail of Paramagnetic behavior at room temperature of Zn1−xMnxTe nanocrystals grown in a phosphate glass matrix by the fusion method

Journal of Alloys and Compounds, 2015

This work reports on the synthesis and characterization of Zn 1-x Mn x Te nanocrystals (NCs) with... more This work reports on the synthesis and characterization of Zn 1-x Mn x Te nanocrystals (NCs) with Mn doping concentration x varying from 0.000 to 0.800. Physical properties of samples were studied by transmission electron microscopy, magnetic force

Research paper thumbnail of Surface and exchange anisotropy fields in MnFe2O4 nanoparticles: Size and temperature effects

Journal of Applied Physics, 1999

Angular measurements of magnetic resonance are used to investigate the surface anisotropy field a... more Angular measurements of magnetic resonance are used to investigate the surface anisotropy field as well as the exchange anisotropy field in spherical MnFe2O4 magnetic nanoparticles as a function of temperature and particle diameter (D). The resonance field is a combination of angular dependent and angular independent fields, both affected by the surface anisotropy field, which in turn follows a D−α power law, with α very close to unity. The angular dependent component probes the surface anisotropy field while the angular independent component probes the exchange anisotropy field. In the temperature range from 100 to 250 K a negative surface anisotropy field is found, which increases as the particle size is reduced, indicating a radial orientation of the spins at the MnFe2O4 nanoparticle surface.

Research paper thumbnail of Light microscopy and magnetic resonance characterization of a DMSA-coated magnetic fluid in mice

IEEE Transactions on Magnetics, 2002

Research paper thumbnail of Morphology in semimagnetic Pb1−xMnxSe nanocrystals: Thermal annealing effects

Applied Physics Letters, 2009

Samples of Pb1−xMnxSe nanocrystals were synthesized by fusion method and characterized by optical... more Samples of Pb1−xMnxSe nanocrystals were synthesized by fusion method and characterized by optical absorption, atomic force microscopy, x-ray diffraction, and electron paramagnetic resonance (EPR) techniques. Effects of Mn2+ ion incorporation into PbSe nanocrystals are manifested by well resolved optical spectra for different concentrations of Mn. The EPR spectra of as grown and thermal annealed Pb1−xMnxSe samples show that the magnetic properties of these Mn-doped nanocrystals can be tuned by thermal processes using different annealing times.

Research paper thumbnail of Evidence of Cd1−xMnxS nanocrystal growth in a glass matrix by the fusion method

Applied Physics Letters, 2008

In this work, CdS nanocrystals (NCs) doped with Mn were synthesized in a glass matrix by fusion. ... more In this work, CdS nanocrystals (NCs) doped with Mn were synthesized in a glass matrix by fusion. The as-grown Cd1−xMnxS NCs were investigated by optical absorption, atomic force microscopy, and electron paramagnetic resonance (EPR). The incorporation of Mn2+ ions in CdS NCs was confirmed by an absorption transition blueshift with increasing Mn concentration x. EPR spectra demonstrated the existence of two distinct Mn2+ ion locations: one incorporated in the core and the other near the surface of the Cd1−xMnxS NCs. The hyperfine interaction constants used to simulate the EPR spectra were A=7.6 and 8.2 mT, respectively. The synthesis of high quality Cd1−xMnxS NCs may allow the control of optical and magnetic properties.

Research paper thumbnail of Ferromagnetic resonance in GdAl2crystals doped with anisotropic rare-earth ions

Journal of Physics C: Solid State Physics, 1984

Ferromagnetic resonance measurements of the magnetic anisotropy and resonance linewidth are repor... more Ferromagnetic resonance measurements of the magnetic anisotropy and resonance linewidth are reported for single-crystal specimens of the cubic Laves-phase intermetallic compound GdAl2 and for RxGd1-xAl2 where R is a heavy rare-earth ion. The doping levels of the samples were: for R=Tb, x=0.0025, 0.01, 0.02, 0.05; for R=Dy, x=0.02; for R=Ho, x=0.02; for R=Er, x=0.01, 0.03. Microwave frequencies close to 9.3,

Research paper thumbnail of Magnetic surface anisotropy and ferromagnetic resonance in GdAl 2 crystals

Journal of Physics F: Metal Physics, 1984

Ferromagnetic resonance observed in a GdAl2 crystal consists of a bulk mode and a surface-induced... more Ferromagnetic resonance observed in a GdAl2 crystal consists of a bulk mode and a surface-induced mode. At 80K the former predominates but, as the temperature is reduced, the relative intensity of this mode decreases and at 20K only the surface-induced mode is observed. At the higher temperature the anisotropy of the field for ferromagnetic resonance is as predicted from the statically measured magnetocrystalline anisotropy, but at 20K this is not so, because the resonance of the surface-induced mode is shifted by magnetic surface anisotropy. Three surface anisotropy constants are needed to describe this effect; their values are estimated as Ku=0.02C, K'u=-0.009C, Kn=0.33C. The value adopted for C=2Ms(2 pi A)1/2 is 1.47 erg cm-2.

Research paper thumbnail of Identification and valuation of paramagnetic radicals in natural dolomites as an indicator of geological events

Physics and Chemistry of Minerals, 2003

Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron ... more Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron paramagnetic resonance (EPR) spectroscopy. The complex spectra in the g ¼ 2.0 region is composed of Mn 2+ lines and signals due to crystallization and radiationinduced defects. Measurements in microwave frequencies of 9.5 GHz (X-band) and 35 GHz (Q-band), and thermal and/or radiation treatments allowed identification of seven paramagnetic radicals in the g ¼ 2.0 region: (1) isotropic organic radical; (2) axial SO À 2 ; (3) axial PO 0 2 or PO 2À 2 ; (4) isotropic CO À 2 ; (5) axial CO À 2 ; (6) axial CO 3À 3 ; (7) isotropic unknown line. The use of these paramagnetic centres as indicators of geological events is discussed.

Research paper thumbnail of Biodistribution and biocompatibility investigation in magnetoliposome treated mice

Spectroscopy, 2004

Magnetoliposomes (ML's) may be successfully applied for several purposes. A dimyristoylphosph... more Magnetoliposomes (ML's) may be successfully applied for several purposes. A dimyristoylphosphatidyl‒choline‒based ML (ML‒2) sample was developed as a precursor of more complex thermal cancer therapy systems. The present study reports on morphology and magnetic resonance (MR) investigations carried out with the magnetite‒based ML‒2 sample. For the experiments, adult female Swiss mice were endovenously treated with a bolus dose of 100 µl of ML‒2. Morphology and room‒temperature MR studies (X‒band experiments) were performed in several organs collected from 1 hour to 28 days after ML administration. Histological data showed magnetic nanoparticle (MNP) clusters up to the 28th day in the liver and spleen tissues. In spite of the presence of MNP clusters, no morphological alterations were observed, supporting the biocompatibility of the ML‒2. MR signal was detected only in the liver and spleen tissues and showed that the MNP's concentration was not altered from 48 hours to 28 days...

Research paper thumbnail of Investigation of the Brownian relaxation and hydrodynamic radius in magnetic nanoparticles

Solid State Communications, 1997

Magnetic resonance is used to estimate the Brownian relaxation time and hydrodynamic radius of Mn... more Magnetic resonance is used to estimate the Brownian relaxation time and hydrodynamic radius of MnFezOd ferrite nanoparticles in suspension in a magnetic fluid. By measuring the resonance linewidth broadening as a function of the particle-particle distance and as a function of the temperature, relaxation time and hydrodynamic radius respectively of the order of 4.8~s and 11.7mn were estimated. The relaxation time falls within the expected range and the hydrodynamic radius is found to be 2.2 times the mean value of the particle radius (54nm), in excellent agreement with the literature.

Research paper thumbnail of Synthesis and magnetic characterization of Pb1−xMnxS nanocrystals in glass matrix

Journal of Physics D: Applied Physics, 2008

The synthesis of manganese-doped PbS (Pb1-xMnxS) nanocrystal (NC) dots within a borosilicate glas... more The synthesis of manganese-doped PbS (Pb1-xMnxS) nanocrystal (NC) dots within a borosilicate glass matrix has been investigated by atomic force microscopy, electron paramagnetic resonance and magnetic measurements. The fusion method was employed in the preparation of the magnetic semiconductor NC dots whereas the measurements performed showed changes in the physical properties of the manganese-doped dots as a result of the

Research paper thumbnail of In vitro toxicity of magnetic fluids evaluated for macrophage cell lines

Journal of Magnetism and Magnetic Materials, 2002

ABSTRACT To determine macrophage cell lines, the analysis of in vitro toxicity of magnetic fluids... more ABSTRACT To determine macrophage cell lines, the analysis of in vitro toxicity of magnetic fluids was discussed. Ferrofluid-dimercaptosuccinic acid (FFDMSA) and dextran-coated ferrofluid (FFDX) were used to determine the viability of the cells. The color of ferrofluids adsorbed or internalized inside the cells impaired the use of metabolic tests based on the production of a chromogen. It was found that the FFDMSA showed a dramatic effect on cell growth whereas FFDX showed a limited toxicity even at high concentration , as compared to the FFDMSA.

Research paper thumbnail of Synthesis of manganese ferrite nanoparticles in macroporous styrene-divinylbenzene copolymer

Journal of Magnetism and Magnetic Materials, 2004

Preparation of manganese ferrite ðMnFe 2 O 4 Þ in a polymer template is described in this work. T... more Preparation of manganese ferrite ðMnFe 2 O 4 Þ in a polymer template is described in this work. The ferrite-based samples were prepared in situ by two routes: (I) alkaline oxidation of Fe 3þ and Mn 2þ ions and (II) alkaline oxidation of Fe 2þ and Mn 2þ ions. The nanocomposites were characterized using chemical analysis, X-ray diffraction, M. ossbauer spectroscopy and magnetic resonance. It was found that route-I produced smaller particles than route-II. This effect can be attributed to the oxidation state of iron ions and their interaction with the polymeric template.

Research paper thumbnail of Ferromagnetic resonance of ferrite ferrofluids at high microwave power levels

Journal of Magnetism and Magnetic Materials, 2004

ABSTRACT

Research paper thumbnail of Use of magnetic resonance to study biodistribution of dextran-coated magnetic fluid intravenously administered in mice

Journal of Magnetism and Magnetic Materials, 2002

... LM Lacava a , ZGM Lacava Corresponding Author Contact Information , E-mail The Corresponding ... more ... LM Lacava a , ZGM Lacava Corresponding Author Contact Information , E-mail The Corresponding Author , a , RB Azevedo a , SB Chaves a , VAP Garcia a , O. Silva b , F. Pelegrini b , N. Buske c , C. Gansau c , MF Da Silva d and PC Morais d. a Dept. ...

Research paper thumbnail of Magnetic resonance investigation of monodisperse oleoylsarcosine-coated magnetic fluid

Journal of Magnetism and Magnetic Materials, 2005

Magnetic resonance experiments were used to investigate the occurrence of particle arrays induced... more Magnetic resonance experiments were used to investigate the occurrence of particle arrays induced by the application of a small steady field (50 G) during the frozen procedure. In order to skip from the size-dependent effects the sample was filtered to a very narrow distribution of particle sizes. Three well-defined components were chosen to fit the envelope resonance line. Analyses of the resonance field versus temperature of each component were used as a support for the occurrence of dimers and tetramers as the dominant magnetic arrays.

Research paper thumbnail of Ferromagnetic resonance line of ferrite ferrofluids at high microwave power

Journal of Magnetism and Magnetic Materials, 2005

... References. [1] P. Kabos, CE Patton, G. Wiese, AD Sullins, ES Wright and L. Chen. J. Appl. Ph... more ... References. [1] P. Kabos, CE Patton, G. Wiese, AD Sullins, ES Wright and L. Chen. J. Appl. Phys., 80 (1996), p. 3962. ... [9] SV Vonsovskii (Ed.), Ferromagnetic Resonance, Pergamon, Oxford, 1966, p. 274.. [10] I. Hrianca, I. Malaescu, F. Claici and CN Marin. J. Magn. Magn. ...

Research paper thumbnail of Long-Term Biodistribution and Biocompatibility Investigation of Dextran-Coated Magnetite Nanoparticle Using Mice as the Animal Model

Journal of Biomedical Nanotechnology, 2012

Magnetic resonance is used to investigate biodistribution aspects of dextran-coated magnetite nan... more Magnetic resonance is used to investigate biodistribution aspects of dextran-coated magnetite nanoparticles (9.4 nm core diameter) in both liver and spleen from 5 minutes up to 6 months after intravenous administration of a magnetic fluid sample in female Swiss mice. Using magnetic resonance data important parameters such as the absorption half-life (t 1/2 = 12 +/- 2 min in the liver and t 1/2 = 11 +/- 2 min in the spleen), the peak time (1.7 +/- 0.2 h in the liver and 1.9 +/- 0.2 h in the spleen), and the disposition half-life of the dextran-coated magnetite nanoparticles in mice organs (t 1/2 = 70 +/- 10 h in the liver and t 1/2 = 32 +/- 7 h in the spleen) were assessed. In addition, light and electron microscopy showed several aspects that may be related to the iron metabolism. Microscopic analysis also revealed that although magnetite nanoparticles or iron released from them are retained in the organism for a long period of time, no morphologic alteration is induced by the intravenous administration of the magnetic fluid sample, evidencing its biocompatibility. The used tests may represent an adequate methodology for nanotoxicology evaluation.

Research paper thumbnail of Control of magnetic behavior by Pb1-xMnxS nanocrystals in a glass matrix

Journal of Applied Physics, 2012

ABSTRACT Diluted magnetic semiconductor nanocrystals, Pb1-xMnxS (x = 0.003, 0.005, and 0.010), of... more ABSTRACT Diluted magnetic semiconductor nanocrystals, Pb1-xMnxS (x = 0.003, 0.005, and 0.010), of approximately 6 nm were successfully grown in a glass matrix by a combination of fusion and thermal annealing. X-ray diffraction measurements reveal that the as-produced nanocrystals (NC), of group IV–VI, are single-phase, nanosized and crystallized in the rock salt structure with replacement of Pb2+-ions by Mn2+-ions. Magnetic force microscopy images also confirmed the high quality of the Pb1-xMnxS NC samples, showing a uniform distribution of total magnetic moments in the nanocrystals. The observation of characteristic hyperfine structures from electron paramagnetic resonance measurements provided evidence for Mn2+ incorporation within the PbS dot structure. Moreover, low temperature magnetization and susceptibility data showed that most of the magnetic ions hosted by the nanocomposite samples are in a paramagnetic state.