Showing papers on "Superparamagnetism published in 2015"

Magnetic Properties of Magnetic Nanoparticles for Efficient Hyperthermia.

Abstract: Localized magnetic hyperthermia using magnetic nanoparticles (MNPs) under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to enhance the power dissipation or heating efficiency of MNPs. Several factors influence the heating efficiency of MNPs, such as the amplitude and frequency of the applied magnetic field and the structural and magnetic properties of MNPs. We discuss some of the physics principles for effective heating of MNPs focusing on the role of surface anisotropy, interface exchange anisotropy and dipolar interactions. Basic magnetic properties of MNPs such as their superparamagnetic behavior, are briefly reviewed. The influence of temperature on anisotropy and magnetization of MNPs is discussed. Recent development in self-regulated hyperthermia is briefly discussed. Some physical and practical limitations of using MNPs in magnetic hyperthermia are also briefly discussed.

Magnetite (Fe 3 O 4 )-filled carbon nanofibers as electro-conducting/superparamagnetic nanohybrids and their multifunctional polymer composites

Abstract: A mild-temperature, nonchemical technique is used to produce a nanohybrid multifunctional (electro-conducting and magnetic) powder material by intercalating iron oxide nanoparticles in large aspect ratio, open-ended, hollow-core carbon nanofibers (CNFs). Single-crystal, superparamagnetic Fe3O4 nanoparticles (10 nm average diameter) filled the CNF internal cavity (diameter <100 nm) after successive steps starting with dispersion of CNFs and magnetite nanoparticles in aqueous or organic solvents, sequencing or combining sonication-assisted capillary imbibition and concentration-driven diffusion, and finally drying at mild temperatures. The influence of several process parameters—such as sonication type and duration, concentration of solids dispersed in solvent, CNF-to-nanoparticle mass ratio, and drying temperature—on intercalation efficiency (evaluated in terms of particle packing in the CNF cavity) was studied using electron microscopy. The magnetic CNF powder was used as a low-concentration filler in poly(methyl methacrylate) to demonstrate thin free-standing polymer films with simultaneous magnetic and electro-conducting properties. Such films could be implemented in sensors, optoelectromagnetic devices, or electromagnetic interference shields.

Photo-fluorescent and magnetic properties of iron oxide nanoparticles for biomedical applications

Abstract: Iron oxide exhibits fascinating physical properties especially in the nanometer range, not only from the standpoint of basic science, but also for a variety of engineering, particularly biomedical applications. For instance, Fe3O4 behaves as superparamagnetic as the particle size is reduced to a few nanometers in the single-domain region depending on the type of the material. The superparamagnetism is an important property for biomedical applications such as magnetic hyperthermia therapy of cancer. In this review article, we report on some of the most recent experimental and theoretical studies on magnetic heating mechanisms under an alternating (AC) magnetic field. The heating mechanisms are interpreted based on Neel and Brownian relaxations, and hysteresis loss. We also report on the recently discovered photoluminescence of Fe3O4 and explain the emission mechanisms in terms of the electronic band structures. Both optical and magnetic properties are correlated to the materials parameters of particle size, distribution, and physical confinement. By adjusting these parameters, both optical and magnetic properties are optimized. An important motivation to study iron oxide is due to its high potential in biomedical applications. Iron oxide nanoparticles can be used for MRI/optical multimodal imaging as well as the therapeutic mediator in cancer treatment. Both magnetic hyperthermia and photothermal effect has been utilized to kill cancer cells and inhibit tumor growth. Once the iron oxide nanoparticles are up taken by the tumor with sufficient concentration, greater localization provides enhanced effects over disseminated delivery while simultaneously requiring less therapeutic mass to elicit an equal response. Multi-modality provides highly beneficial co-localization. For magnetite (Fe3O4) nanoparticles the co-localization of diagnostics and therapeutics is achieved through magnetic based imaging and local hyperthermia generation through magnetic field or photon application. Here, Fe3O4 nanoparticles are shown to provide excellent conjugation bases for entrapment of therapeutic molecules, fluorescent agents, and targeting ligands; enhancement of solid tumor treatment is achieved through co-application of local hyperthermia with chemotherapeutic agents.

Magnetic multi-granule nanoclusters: A model system that exhibits universal size effect of magnetic coercivity

Abstract: Magnetic multi-granule nanoclusters: A model system that exhibits universal size effect of magnetic coercivity

NiO Nanoparticles: Synthesis and Characterization

Abstract: In the current paper,Nanostructured Nickel oxide (NiO) were synthesized by co-precipitation method using Nickel(II) Chloride Hexahydrate (NiCl2.6H2O) and sodium hydroxide (NaOH) as starting material. Structural, optical and magnetic properties of nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Atomic force microscope (AFM), UV–Vis absorption; Fourier transformed infrared (FTIR) and vibrating sample magnetometer (VSM) technique. The X-ray diffraction pattern studies revealed the NiO have a face-centered cubic (FCC) structure and confirmed the presence of high degree of crystallinity nature NiO nanoparticles that their average size is found to be 26 nm. The composition of nanostructures confirmed by analysis of FTIR spectra. The average size of the NiO nanoparticle observed from scanning electron microscopy images is found to be dimensions about 24 nm. Magnetic measurement confirmed the Nickel Oxide nanostructures superparamagnetic behavior at room temperature (RT) after calcinations.

Nanocluster of superparamagnetic iron oxide nanoparticles coated with poly (dopamine) for magnetic field-targeting, highly sensitive MRI and photothermal cancer therapy

Abstract: In this paper, a core–shell nanocomposite of clusters of superparamagnetic iron oxide nanoparticles coated with poly(dopamine) (SPION clusters@PDA) is fabricated as a magnetic field-directed theranostic agent that combines the capabilities of highly sensitive magnetic resonance imaging (MRI) and photothermal cancer therapy. The highly concentrated SPION cluster core is suitable for sensitive MRI due to its superparamagnetic properties, and the poly(dopamine) coating layer can induce cancer cell death under near-infrared (NIR) laser irradiation because of the photothermal conversion ability of PDA. MRI scanning reveals that the nanocomposite has relatively high r2 and r2(*) relaxivities, and the r2(*) values are nearly threefold higher than the r2 values because of the clustering of the SPIONs in the nanocomposite core. Due to the rapid response to magnetic field gradients, enhanced cellular uptake of our nanocomposite mediated by an external magnetic field can be achieved, thus producing significantly enhanced local photothermal killing efficiency against cancer cells under NIR irritation.

Facile Synthesis of Well-Dispersed Superparamagnetic γ-Fe2O3 Nanoparticles Encapsulated in Three-Dimensional Architectures of Cellulose Aerogels and Their Applications for Cr(VI) Removal from Contaminated Water

Abstract: With the increasing emphasis on green chemistry, cellulose aerogels that consist of abundant three-dimensional (3D) architectures have been considered as a class of idea green matrix materials to encapsulate various nanoparticles for synthesis of miscellaneous functional materials. Herein, a facile template synthesis combined with chemical coprecipitation was implemented to prepare hybrid γ-Fe2O3@cellulose aerogels (γ-Fe2O3@CA). The γ-Fe2O3 nanoparticles are well dispersed and immobilized in the micro/nanoscale pore structure of the aerogels, and exhibit superparamagnetic behavior. The particle sizes, pore characteristic parameters, magnetic property, and mechanical strength of the synthetic γ-Fe2O3@CA could be flexibly tailored by adjusting the concentrations of the initial reactants. In addition, γ-Fe2O3@CA exhibits rapid adsorption rate and excellent adsorption ability to remove Cr(VI) heavy metal ions. Moreover, combined with the advantages of environmental benefits, facile convenient preparation meth...

The impact of polymer coatings on magnetite nanoparticles performance as MRI contrast agents: a comparative study.

Abstract: Superparamagnetic iron oxide nanoparticles (SPIONs) are the most commonly used negative MRI contrast agent which affect the transverse (T2) relaxation time. The aim of the present study was to investigate the impact of various polymeric coatings on the performance of magnetite nanoparticles as MRI contrast agents. Ferrofluids based on magnetite (Fe3O4) nanoparticles (SPIONs) were synthesized via chemical co-precipitation method and coated with different biocompatible polymer coatings including mPEG-PCL, chitosan and dextran. The bonding status of different polymers on the surface of the magnetite nanoparticles was confirmed by the Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The vibrating sample magnetometer (VSM) analysis confirmed the superparamagnetic behavior of all synthesized nanoparticles. The field–emission scanning electron microscopy (FE-SEM) indicated the formation of quasi-spherical nanostructures with the final average particle size of 12–55 nm depending on the type of polymer coating, and X-ray diffraction (XRD) determined inverse spinel structure of magnetite nanoparticles. The ferrofluids demonstrated sufficient colloidal stability in deionized water with the zeta potentials of −24.2, −16.9, +31.6 and −21 mV for the naked SPIONs, and for dextran, chitosan and mPEG-PCL coated SPIONs, respectively. Finally, the magnetic relaxivities of water based ferrofluids were measured on a 1.5T clinical MRI instrument. The r2/r1 value was calculated to be 17.21, 19.42 and 20.71 for the dextran, chitosan and mPEG-PCL coated SPIONs, respectively. The findings demonstrated that the value of r2/r1 ratio of mPEG-PCL modified SPIONs is higher than that of some commercial contrast agents. Therefore, it can be considered as a promising candidate for T2 MRI contrast agent.

Internal Magnetic Structure of Nanoparticles Dominates Time-Dependent Relaxation Processes in a Magnetic Field

Abstract: Magnetic nanoparticles provide a unique combination of small size and responsiveness to magnetic fields making them attractive for applications in electronics, biology, and medicine. When exposed to alternating magnetic fields, magnetic nanoparticles can generate heat through loss power mechanisms that continue to challenge a complete physical description. The influence of internal nanoparticle (intracore) magnetic domain structure on relaxation remains unexplored. Within the context of potential biomedical applications, this study focuses on the dramatic differences observed among the specific loss power of three magnetic iron oxide nanoparticle constructs having comparable size and chemical composition. Analysis of polarization analyzed small angle neutron scattering data reveals unexpected and complex coupling among magnetic domains within the nanoparticle cores that influences their interactions with external magnetic fields. These results challenge the prevailing concepts in hyperthermia which limit consideration to size and shape of magnetic single domain nanoparticles.

Preparation of magnetic metal–organic framework nanocomposites for highly specific separation of histidine-rich proteins

Abstract: This work reports a novel metal-organic framework (MOF)-based metal affinity platform for the rapid and highly specific separation of histidine-rich proteins using zeolitic imidazolate framework-8 coated magnetic nanocomposites (denoted as Fe3O4@ZIF-8). The coating of the ZIF-8 layer on the Fe3O4 core was performed in aqueous solution at room temperature and merely took 10 minutes. The monodisperse Fe3O4@ZIF-8 has an average diameter of 190 nm, displays superparamagnetism with a saturation magnetization value of 47.9 emu g-1, and possesses a large external surface area of 131.0 m2 g-1. Due to the high density of low-coordinated Zn atoms on the surface of ZIF-8, Fe3O4@ZIF-8 exhibited a large adsorption capacity for model histidine-rich proteins (>6000 mg g-1 for bovine hemoglobin) and relatively low adsorption capacities for other proteins which contain fewer surface-exposed histidine residues. Moreover, Fe3O4@ZIF-8 showed excellent recyclability (more than 10 times) with high recovery (88.4%). In addition, Fe3O4@ZIF-8 can be used to selectively separate hemoglobin from a protein mixture and human blood samples. The good results demonstrate the potential of Fe3O4@ZIF-8 in the separation of histidine-rich proteins.

Water-dispersible ascorbic-acid-coated magnetite nanoparticles for contrast enhancement in MRI

Abstract: Superparamagnetic iron oxide nanoparticles of size ~5 nm surface functionalized with ascorbic acid (vitamin C) form a stable dispersion in water with a hydrodynamic size of ~30 nm. The anti-oxidant property of ascorbic acid is retained after capping, as evidenced from the capability of converting methylene blue to its reduced leuco form. NMR relaxivity studies show that the ascorbic-acid-coated superparamagnetic iron oxide aqueous nanofluid is suitable as a contrast enhancement agent for MRI applications, coupled with the excellent biocompatibility and medicinal values of ascorbic acid.

Multilayer fluorescent magnetic nanoparticles with dual thermoresponsive and pH-sensitive polymeric nanolayers as anti-cancer drug carriers

Abstract: A multi-step process was used to synthesize fluorescent folic acid (FA)-conjugated stimuli-responsive magnetic nanoparticles as anti-cancer drug nanocarriers. Sol–gel processing of tetraethyl orthosilicate and fluorescein isothiocyanate-conjugated 3-aminopropyltriethoxysilane was used to synthesize Fe3O4@SiO2–FITC followed by the distillation precipitation polymerization of 2-hydroxyethyl methacrylate and N,N′-methylenebis(acrylamide) to obtain Fe3O4@SiO2@P(HEMA) nanoparticles. Conjugating with FA and RAFT agent, Fe3O4@SiO2@P(HEMA)@P(NIPAAM-co-AA) nanoparticles were synthesized via the polymerization of N-isopropylacrylamide and acrylic acid. The core–shell structure of nanoparticles was revealed via TEM. Furthermore, the progression of each step was studied by means of FT-IR and TGA. VSM and XRD were used to show that the synthesized nanoparticles retain their superparamagnetic properties. The synthesized nanoparticles exhibited dual thermo- and pH-sensitive behaviours. These nanoparticles were used as nanocarriers of the anti-cancer drug doxorubicin via controlled release in simulated physiological and acidic conditions. In addition, the synthesized nanoparticles showed a relatively non-toxic nature to HeLa cells, whereas cell viability decreased significantly when cells were incubated with DOX-loaded nanoparticles.

Functionalization of Strongly Interacting Magnetic Nanocubes with (Thermo)Responsive Coating and Their Application in Hyperthermia and Heat-Triggered Drug Delivery

Abstract: Herein, we prepare nanohybrids by incorporating iron oxide nanocubes (cubic-IONPs) within a thermoresponsive polymer shell that can act as drug carriers for doxorubicin(doxo). The cubic-shaped nanoparticles employed are at the interface between superparamagnetic and ferromagnetic behavior and have an exceptionally high specific absorption rate (SAR), but their functionalization is extremely challenging compared to bare superparamagnetic iron oxide nanoparticles as they strongly interact with each other. By conducting the polymer grafting reaction using reversible addition–fragmentation chain transfer (RAFT) polymerization in a viscous solvent medium, we have here developed a facile approach to decorate the nanocubes with stimuli-responsive polymers. When the thermoresponsive shell is composed of poly(N-isopropylacrylamide-co-polyethylene glycolmethyl ether acrylate), nanohybrids have a phase transition temperature, the lower critical solution temperature (LCST), above 37 °C in physiological conditions. Do...

Pb(II) Adsorption Onto a Magnetic Composite of Activated Carbon and Superparamagnetic Fe3O4 Nanoparticles: Experimental and Modeling Study

Abstract: Magnetic separation technology has been extensively used in the field of environmental problems, due to solving difficulties resulted from filtration and centrifuging. In this study, powder activated carbon (PAC) was magnetized by magnetite nanoparticles (Fe3O4@C) as an adsorbent for lead ions (Pb2+) from aqueous solution. The characteristics of the modified PAC were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, Brunauer-Emmett-Teller surface area analysis, energy dispersive X-ray spectroscopy, and vibrating sample magnetometry. Batch adsorption experiments were conducted as a function of pH, contact time, adsorbent dosage and initial Pb2+ concentration, and solution temperature. The equilibrium isotherm and kinetic models were used to evaluate the fitness of the experimental data. The maximum mono-layer adsorption capacity of Pb2+ was 71.42 mg/g at 50°C. It could also be shown that the sorption isotherms were well described by the Langmuir equilibrium model. The kinetic of the adsorption process was found to follow the pseudo-second-order model expression. Thermodynamic studies indicated that the adsorption process was feasible, spontaneous, and endothermic. Desorption experiments exhibited that the Fe3O4@C had a good potential in regard to regeneration and reusability and is easily regenerated by HCl solution. The proposed adsorption process can be a promising technique for Pb2+ removal from aqueous solutions and to be used in full-scale and industrial applications.

Fe3O4@ZIF-8: magnetically recoverable catalysts by loading Fe3O4 nanoparticles inside a zinc imidazolate framework.

Abstract: A simple methodology for encapsulating ca. 10 nm-sized superparamagnetic Fe3O4 nanoparticles in zeolitic imidazolate frameworks (ZIF-8) crystals was developed. The corresponding Fe3O4@ZIF-8 heterostructured material exhibits bifunctional properties with both high magnetization (Fe3O4) and high thermal stability, large specific surface, and catalytic properties (ZIF-8). The Fe3O4@ZIF-8 catalyst exhibits fair separation ability and reusability, which can be repeatedly applied for Knoevenagel condensations and Huisgen cycloadditions for at least ten successive cycles.

Superparamagnetism and metamagnetic transition in Fe3O4 nanoparticles synthesized via co-precipitation method at different pH

Abstract: In the present work, Fe 3 O 4 nanoparticles have been synthesized via low temperature co-precipitation method at different pH (70, 110 and 124) with the aim to study the variation of pH on the structural, optical and magnetic properties of samples Further, the sample synthesized at pH ~124 has been annealed at 230 °C for 10 h to study the effect of annealing on structural, optical and magnetic properties X-ray diffraction (XRD) results reveal the formation of pure spinel phase with the space group Fd-3m Further, XRD, FESEM and TEM results confirm the nanocrystalline nature of the as synthesized samples, and the particle size of the samples decreases as the pH increases and increases after annealing at 230 °C FTIR analysis indicates that the sample synthesized at pH ~124 and the same sample annealed at 230 °C are pure spinel Fe 3 O 4 , whereas the samples synthesized at pH ~70 and 110 have small content of α-Fe 2 O 3 The optical measurements of the as synthesized samples show two band gaps in all synthesized samples Field dependent magnetization measurements ( M–H ) reveal superparamagnetic nature of all the synthesized samples at room temperature and ferromagnetic behavior at low temperature (~5 K) Furthermore, M–H plots measured at 5 K show presence of metamagnetic transition in all samples The metamagnetic transition along with ferromagnetic behavior at low temperature in Fe 3 O 4 nanoparticles are observed first time in the present work to the best of our knowledge Further the value of magnetization decreases with decreasing particle size at both temperatures The fitting of the field cooled (FC) temperature dependent magnetization ( M–T ) measurements data with modified Bloch-spin wave model with additional surface disorder term and mixed magnetic phases indicates surface spin disorder and mixed magnetic phases in the as synthesized samples, which may be the possible reason for the existence of metamagnetic transition in the samples The correlation between the observed magnetic properties and structural characteristics of the samples with the synthesizing parameters (pH value and annealing effect) has been described and discussed in this paper

Influence of microwave power on the preparation of NiO nanoflakes for enhanced magnetic and supercapacitor applications.

Abstract: Nanoflake-structured NiO were synthesized by a microwave assisted method without the use of additives. The cubic phase of NiO nanoparticles with increasing crystalline nature for higher microwave power is ascertained by X-ray diffraction studies. Previous reports revealed that hexagonally structured β-Ni(OH)2 was completely transferred into the cubic phase of NiO around 350 °C, confirmed by using thermal analysis (TG/DTA). In our present work, the size and morphology of nanoparticles are ascertained from transmission electron microscopy (TEM) analysis. Flake-like morphology with uniform size, shape and less agglomerated structure formation is obtained for 900 and 600 W of microwave power used for the synthesis of NiO samples. The effect of microwave power used for the synthesis of NiO nanoflakes was analyzed by studying the magnetic and electrochemical behavior of NiO nanoflakes. Room temperature magnetic measurements revealed the small ferromagnetic nature of NiO nanoparticles. It was observed that the samples synthesized at higher microwave power exhibited divergence behavior below 300 K in FC and ZFC measurements, which results superparamagnetic behavior. An enhanced supercapacitor performance with higher specific capacitance values was determined for NiO nanoflake samples synthesized at 25600 W and 900 W of microwave power.