Dynamics of Superparamagnetic Iron Oxide Nanoparticles with Various Polymeric Coatings (original) (raw)
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Journal of Alloys and Compounds, 2014
We have synthesized the maghemite (g-Fe 2 O 3 ) nanoparticles by a chemical coprecipitation technique of ferric and ferrous ions in alkali solution through the pipette drop method (pipette diameter: 2000 mm) and the piezoelectric nozzle method (nozzle size: 50 mm). The microstructures of nanoparticles were characterized by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The size distribution of the maghemite nanoparticles prepared by typical pipette drop method is from 5 to 8 nm. However, the nanoparticles made by piezoelectric nozzle method shows a small size and a very narrow size distribution from 3 to 5 nm. Zero-field-cooling (ZFC) and field-cooling (FC) magnetization measurements were performed using a superconducting quantum interference device magnetometer from 2 to 300 K to investigate the magnetic properties of nanoparticles. The FC/ZFC magnetization measurements showed a typical superparamagnetic behavior with very narrow size distribution. r
Journal of Nanoparticle Research, 2012
This article presents the synthesis and characterization of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) coated with ultrathin layer of anionic derivative of chitosan. The water-based fabrication involved a two-step procedure. In the first step, the nanoparticles were obtained by co-precipitation of ferrous and ferric aqueous salt solutions with ammonia in the presence of cationic derivative of chitosan. In the second step, such prepared materials were subjected to adsorption of oppositely charged chitosan derivative which resulted in the preparation of negatively charged SPIONs. They were found to develop highly stable dispersion in water. The core size of the nanocoated SPIONs, determined using transmission electron microscopy, was measured to be slightly above 10 nm. The coated nanoparticles form aggregates with majority of them having hydrodynamic diameter below 100 nm, as measured by dynamic light scattering. Their composition and properties were studied using FTIR and thermogravimetric analyses. They exhibit magnetic properties typical for superparamagnetic material with a high saturation magnetization value of 123 ± 12 emu g-1 Fe. Very high value of the measured r 2 relaxivity, 369 ± 3 mM-1 s-1 , is conducive for the potential application of the obtained SPIONs as promising contrast agents in magnetic resonance imaging.
Materials
This paper reports the characterization of iron oxide magnetic nanoparticles obtained via the thermal decomposition of an organometallic precursor, which were then loaded into nanocapsules prepared via the emulsification process in the presence of an amphiphilic derivative of chitosan. The applied synthetic method led to the formation of a hydrophobic layer on the surface of nanoparticles that enabled their loading in the hydrophobic liquid inside of the polymer-based capsules. The average diameter of nanoparticles was determined to be equal to 15 nm, and they were thoroughly characterized using X-ray diffraction (XRD), magnetometry, and Mössbauer spectroscopy. A core–shell structure consisting of a wüstite core and maghemite-like shell was revealed, resulting in an exchange bias effect and a considerable magnetocrystalline anisotropy at low temperatures and a superparamagnetic behavior at room temperature. Importantly, superparamagnetic behavior was observed for the aqueous dispers...
Hyperfine Interactions, 2000
The effect of the surface coating on the magnetic properties of superparamagnetic iron oxide nanoparticles (SPION) with 8 nm in size has been studied. Four different biocompatible coating layers are considered: poly L,L-lactic acid (PLLA), poly ε-caprolactone (PCL), bovine serum albumin (BSA) and gold. The presence of coating layer on the surface of SPION is confirmed by FT-IR spectroscopy. Mössbauer spectroscopy and magnetic susceptibility measurements show that for uncoated SPION and Au@SPION the superparamagnetic fraction is retained. The formation of clusters in the case of BSA@SPION and chain-like structure for PCL@SPION and PLLA@SPION increase the inter-particle interactions resulting in hyperfine magnetic structure observed in the Mössbauer spectra at ambient temperature.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
Superparamagnetic iron oxide nanoparticles (SPIONs) coated with oleic acid were encapsulated into poly(d,l-lactide-co-glycolide) (PLGA) particles using an oil-in-water-in-oil emulsion technique. The use of the oleic acid-coated SPIONs, and their suspension in the first oil phase led to well-dispersed nanoparticles in the PLGA matrix. Relative amounts of SPIONs encapsulated in PLGA could be varied by increasing the concentration of SPIONs in the first oil phase: doubling the amount in that phase doubled the amount of SPIONs in the PLGA. The saturation magnetization scaled proportionally with the amount of SPIONs in the PLGA and was significantly larger than other efforts to encapsulate magnetic nanoparticles in PLGA. Size of the composite particles, as determined by dynamic light scattering (DLS), could be varied from 280 to 160 nm by varying either power or time of sonication while the zeta potential remained near −20 mV for the composite, independent of SPION content. Transmission electron microscopy images showed SPIONs ranging in diameter from 5 to 15 nm embedded inside the polymer and indicated that they were uniformly dispersed within the PLGA particles. Small angle X-ray scattering (SAXS) showed that only the particles containing the largest amount of encapsulated SPIONs displayed a peak indicative of aggregation.
Journal of Materials & Environmental Sustainability Research
Gold-coated magnetic nanoparticles have received a lot of attention in recent years due to their multifunctional attributes and their prospective unique characteristics in environmental and biomedical applications. This paper reports the textural, thermo-gravimetric, and magnetic properties of green synthesized gluconic acid-capped uncoated and gold-coated superparamagnetic iron oxide nanoparticles (SPION@Au). The as-synthesized nanomaterials were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), and superconducting quantum interference device (SQUID) magnetometry. The XRD and SEM measurements showed that the gluconic acid-capped magnetic core was coated with gold with cubical spinel crystalline structures. TGA results revealed the thermal stability of the nanoparticles. Textural properties indicated that the gold-coated nanoparticles were in naturally mesoporous and e...
Journal of Nanoparticle Research, 2012
Superparamagnetic iron oxide nanoparticles (SPIONs) exhibit unique magnetic properties that make them highly efficacious as MR imaging contrast agents and laboratory diagnostic tools. The complexity of SPION magnetic behavior and the multiple parameters affecting this behavior complicate attempts at fabricating particles suited for a particular purpose. A mathematical model of SPION magnetic properties derived from experimental relationships and first principles can be an effective design tool for predicting particle behavior before materials are fabricated. Here, a novel model of SPION magnetic properties is described, using particle size and applied magnetic field as the primary variable inputs. The model is capable of predicting particle susceptibility and non-linear particle magnetization as well as describing the vector magnetic field produced by a single particle in an applied field. Magnetization values produced by the model agree with recent experimental measurements of particle magnetizations. The model is used to predict the complex magnetic behavior of clustered magnetic particles in simulated in vivo environment; specifically, interactions between the clusters and water molecules. The model shows that larger particles exhibit more linear magnetic behavior and stronger magnetization and that clusters of smaller particles allow for more numerous SPION-water molecule interactions and more uniform cluster magnetizations.
Size dependent magnetic properties of iron oxide nanoparticles
Journal of Magnetism and Magnetic Materials, 2003
Uniform iron oxide nanoparticles in the size range from 10 to 24 nm and polydisperse 14 nm iron oxide particles were prepared by thermal decomposition of Fe(III) carboxylates in the presence of oleic acid and co-precipitation of Fe(II) and Fe(III) chlorides by ammonium hydroxide followed by oxidation, respectively. While the first method produced hydrophobic oleic acid coated particles, the second one formed hydrophilic, but uncoated, nanoparticles. To make the iron oxide particles water dispersible and colloidally stable, their surface was modified with poly(ethylene glycol) and sucrose, respectively. Size and size distribution of the nanoparticles was determined by transmission electron microscopy, dynamic light scattering and X-ray diffraction. Surface of the PEG-functionalized and sucrose-modified iron oxide particles was characterized by Fourier transform infrared (FT-IR) and Raman spectroscopy and thermogravimetric analysis (TGA). Magnetic properties were measured by means of vibration sample magnetometry and specific absorption rate in alternating magnetic fields was determined calorimetrically. It was found, that larger ferrimagnetic particles showed higher heating performance than smaller superparamagnetic ones. In the transition range between superparamagnetism and ferrimagnetism, samples with a broader size distribution provided higher heating power than narrow size distributed particles of comparable mean size. Here presented particles showed promising properties for a possible application in magnetic hyperthermia.