Papers by Keyword: Superparamagnetism

Abstract: Fe₃O₄/Hydroxyapatite (HA)-(3-Aminopropyl)triethoxysilane (APTES) nanocomposite as a drug delivery agent was successfully synthesized. The nanocomposite was characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometer (VSM), and ultraviolet-visible (UV-Vis) spectroscopy to investigate the structural, morphology, magnetic properties, and DOX drug loading and release efficiency. The XRD pattern of Fe₃O₄ /HA-APTES nanocomposite showed the formation of two phases with cubic spinel structure for Fe₃O₄ and hexagonal structure for HA. The SEM image showed that the nanocomposite morphology tended to be granular (though not perfectly granular) with a particle size distribution of 65.9 nm. The functional groups detected from the FTIR results were Fe-O at 422–602 cm^-1, indicating Fe₃O₄. Furthermore, vibrations of the phosphate group (PO₄^3-) and Si-O-C appeared at 1037 cm^-1 and 1048 cm^-1, which are characteristic of the phosphate stretch in the HA and APTES. The Fe₃O₄/HA-APTES nanocomposite exhibited superparamagnetic properties with a saturation magnetization value of 19.37 emu/g. As a drug delivery agent, the Fe₃O₄/HA-APTES nanocomposite has a DOX loading efficiency of 5.79 mg/g up to 96.51% for eight hours and a release of 16.36% over 300 min.

Abstract: Spinel ferrite nanoparticles are potential candidates for multiple biomedical applications. Spinel ferrite nanoparticles have been studied extensively for understanding physical, chemical, electro-optical as well as magnetic properties which are fascinating due to cationic distributions corresponding to tetrahedral sites and octahedral sites in a cubic phase. Biocompatibility and large magnetic moment are basic requirements in spinel ferrite nanoparticles for efficient functioning in specific application purpose. Fe₃O₄ (magnetite) is an important member of spinel ferrite group with high chemical stability and ferrimagetic material property at nanodimension. Superparamagnetic state and biocompatibility of magnetite (Fe₃O₄) spinel ferrite nanoparticle has already been proven. Spinel ferrite magnetite nanoparticles have been developed based on precipitation of iron oxide using ferric and ferrous ions at the ratio 2:1 in alkaline media at and above 100°C. The experimental parameters have been set to synthesize pure and uniformly sized magnetite nanoparticles. No other phases of iron oxides were detected other than magnetite spinel phase in the XRD result. The average crystal size has been determined from XRD peak broadening. Absorption spectra were investigated using UV-Vis Spectrometer and FTIR. Thermal and magnetic measurements were carried out Digital Scanning Calorimeter and SQUID Magnetometer. One sample of the prepared nanoparticles with polymer coating of polyvinyl alcohol has been studied for superparamagnetic nature. Superparamagnetic particles show saturation value of magnetization 51.26 emu/g at 100 K. ZFC-FC curves for two samples with polymer coating of polyvinyl alcohol and hydroxy-propyl methyl cellulose have also been studied. Keywords: Spinel Ferrite, Magnetite, Ferrimagnetism, Transition metal oxide, Superparamagnetism. Statements and declarations Competing Interests: The authors declare that there is no competing financial interest that are related directly or indirectly to the reported work in this paper. Conflict of interest: There is no conflict of interest. Acknowledgements The Authors are grateful to IISER Bhopal, CRF facility for providing instrumentation facility to characterize magnetic properties. We acknowledge thanks to Lovely Professional University for providing us necessary characterization technique for the XRD analysis and thermal analysis.

Abstract: The article presents a study of the transport properties of high-temperature superconducting compounds of the Y-Ba-Cu-O system with the addition of the carbon nanomaterial (carbon nanotubes) "Taunite" in different concentrations. According to the data of X-ray phase analysis, scanning electron microscopy and magnetic measurements, it was determined that the carbon nanotube "Taunite" contains ferro-and superparamagnetic particles (~ 30 nm). The dependences of the resistance of the samples on the temperature have been constructed, and the temperature of the transition of the samples to the superconducting state (~ 90 K) has been determined, and the features ("stages") on the resistance curves are observed below. Nickel nanoparticles in the carbon nanotubes "Taunite" have been established to not affect the critical temperature of the superconducting transition, yet after reaching a certain concentration, they destroy the superconducting state.

Abstract: The article examines the effect of nickel nanoparticles on the magnetic properties of the YBCO superconductor. The ceramics were obtained by solid-phase synthesis using yttrium oxide, copper (II) oxide, and barium carbonate with the addition of carbon nanotubes "Taunite" of different concentrations (0, 20, 50, 70, 100 mg). Magnetic studies have demonstrated that ferromagnetism and superparamagnetism are both observed in the samples, which can be explained by the presence of nickel particles. The dependences of the magnetization in the applied magnetic field of the sample without the addition of the carbon nanotubes "Taunite" have a paramagnetic course, and their slope monotonically increased with decreasing temperature. The coercive force of the samples and the value of the magnetic moment has been determined to increase upon the decrease in temperature. The high homogeneity of the heterostructures has been demonstrated in the graphs of FC/ZFC explained by the uneven distribution of nickel nanoparticles, which do not integrate into the crystal lattice and, due to the long-range order of interaction, do not make a strong contribution to the magnetization.

Abstract: Ising core-shell model was proposed to reconstruct superparamagnetism hysteresis in nano-goethite (α-FeOOH). Core and shell set as antiferromagnetic and paramagnetic state respectively. Core and shell radius varies until the theoretical hysteresis fit with experiment hysteresis. At low temperature, the hysteresis reconstructed nicely with 55% antiferromagnetic core contribution and 45% paramagnetic shell contribution. At high temperature, the core-shell model show unrealistic result compared to the pure paramagnetic state.

Abstract: Magnetic nanoparticles (MNPs) have many uses for biomedical applications including drug delivery, magnetic resonance imaging (MRI) contrast agents, theranostics and hyperthermia. MNPs photo-thermally heated by laser light could be used to treat the typically difficult to access tumors such as glioblastomas. Due to their high magnetic saturation, monometallic iron nanoparticles would have an edge over iron oxide nanoparticles currently being investigated for hyperthermia. The goal of this study was to synthesize spherical iron nanoparticles less than 10 nm in diameter by thermal decomposition. The ability of various biocompatible coatings to protect the metallic iron nanoparticles from oxidation was investigated. Coatings studied included Brij, polyethylene glycol and iron oxide. Transmission electron microscopy and Mössbauer spectroscopy were utilized to characterize the coated and uncoated iron nanoparticles’ size and oxidation state to evaluate the effectiveness of the coatings and the procedures in which the coatings were applied. A ferrite shell was found to provide the best stabilization; however, its longer synthesis time increased particle size distribution. Polymer coatings provided biocompatibility but did not prevent oxidation.

Abstract: Rapid preparation of nanocrystalline γ-Fe₂O₃ powder with superparamagnetism was realized by cryomilling commercial Fe₂O₃ powder using liquid nitrogen. The effects of milling temperature and duration on the grain size, phase and microstructure of the nanocrystalline Fe₂O₃ powder were analyzed. Magnetic property of the nanocrystalline γ-Fe₂O₃ powder was also tested by magnetometer at room temperature. The results demonstrate that nanocrystalline γ-Fe₂O₃ powder with single phase can be prepared rapidly by cryomilling with liquid nitrogen. The mean particle size of γ-Fe₂O₃ powder can be reduced from 300 nm to 13 nm by cryomilling at −130 °C within 3 hours. The nanocrystalline γ-Fe₂O₃ powder shows superparamagnetism at room temperature.

Abstract: In the work reported here the magnetic properties of nanocomposite system composed of polystyrene (PS) latex polymer and superparamagnetic nanoparticles (MNPs), is presented. A series of mixtures were prepared by mixing of PS latex dispersion with different amount of MNPs and drop casting on glass substrates at room temperature. After drying, film samples were annealed at 250 °C for 10 min. Morphological changes of the films were examined by scanning electron microscopy (SEM) and magnetic properties studied using vibrating sample magnetometer (VSM) as a function of MNPs content. The saturation magnetization (M_s) of composites increased as MNPs content increased. M_s showed two maxima at 50 wt% and 85 wt% MNPs contents with M_s values of 0.014 emu and 0.020 emu, respectively. The morphological changes of PS/MNPs composite films were also found consistent with these results indicating that magnetic properties these composites can be readily tuned by varying MNPs content.

Abstract: Colloidal particles based on iron oxides and silica were obtained by sol-gel method. Hysteresis curves at various temperatures were built by MPMS SQUID VSM. Theoretically calculated values of samples remanent magnetization were compared to experimental data. Despite of the average particles size about 10 nm sample has remanent magnetic moment. The phenomena may be explained on the basis of magnetostatic interaction between particles. The magnetic state of analyzed samples can be conditional on the presence of several phases with very different magnetic properties or the size effect.

Abstract: The work deals with the study of electrical and magnetic properties of Magnesium-Chromium and Cobalt-Chromium nanoFerrites for their potential applications synthesized by Citrate-Gel auto-combustion method. Structural Characterization of prepared nanoferrites was performed using XRD, SEM, EDS and TEM. XRD patterns confirmed the formation of homogeneous single phased cubic spinel belonging to the space group Fd3m (in agreement with ICSD Ref. data). It is found that crystallite size of Mg-Cr ferrites was in the range of 7-23nm and that of Co-Cr nanoferrites in the range of 6-12 nm. Structural morphology of both the ferrites was studied by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). Elemental compositional analysis was carried out by EDS.Electrical properties such as D.C. resistivity of prepared Mg-Cr and Co-Cr nanoferrites were studied by two probe method. The dielectric measurements as a function of frequency at room temperature were performed in the frequency range of 20Hz to 2MHz using LCR meter. Various dielectric parameters like dielectric constant (ε′), dielectric loss (ε′′) and dielectric loss tangent (tan δ) were measured as a function of frequency. The magnetization measurements of the prepared nanoferrite samples were carried out at room temperature in the applied field of ±15KOe using Vibrating Sample Magnetometer (VSM). From the obtained M-H loops, various magnetic parameters such as Saturation Magnetization (M_s), Coercivity (H_c) and Remanence Magnetization (M_r) were measured. Magnetization as a function of field (±10T) at 5K, 25K, 300K temperatures was measured using VSM. Super-paramagnetic nature of some specified samples in Mg-Cr nanoferrites system was investigated from the temperature dependence of both the field cooled (FC) and the zero-field cooled (ZFC) magnetization measurements under a field of 100 Oe in the temperature range 5K to 350K.From the results of D.C. resistivity measurements it is observed that the resistivity decreases with increase in temperature for both Mg-Cr and Co-Cr nanoferrites suggesting the semiconducting behavior of the samples. Dielectric measurements suggest that the conduction in the ferrite systems may be due to the polaron hopping mechanism. The low loss tangent values at high frequency show the potential applications of these materials in high frequency microwave devices. Mg-Cr nanoferrites were synthesized yielding narrow hysteresis loops which are the characteristic of very soft magnetic materials that are desirable for their utility in Transformers, Inductor cores, Microwave devices and Magnetic shielding. Hysteresis loops of Co-Cr nanoferrites show the medium hard magnetic behavior of the materials. MgFe₂O₄ shows superparamagnetic behavior above room temperature and MgCr_0.9Fe_1.1O₄ shows superparamagnetic behavior with the blocking temperature 94.5K. Hence these nanoferrites find applications in targeted drug delivery and in Magnetic Resonance Imaging (MRI) in biomedical field. The observed results can be explained in detail on the basis of composition and crystallite size.Contents of Paper