Search results for "Superparamagnetism"
showing 10 items of 54 documents
Atmospheric Corrosion Investigation in Industrial, Marine and Rural Environments in South-East Brazil
2002
ASTM 283-C, AISI 304 and 316-L steel specimens (called coupons) were exposed in marine, industrial and rural area(s) for different periods ranging between 1–12 months, in four different season campaigns. The corrosion rate was determined by chemical loss measurements. Rust characterization was performed by XRD, SEM, optical, and Mossbauer spectroscopy (in transmission and backscattering geometry). Superparamagnetic maghemite and goethite were found as corrosion products. Magnetic goethite and feroxyhite decrease with time of exposure. Lepidochrosite is detected and its intensity increase with the atmospheric exposure time. The results obtained from XRD and Mossbauer are in good agreement.
Reversible Supracolloidal Self-Assembly of Cobalt Nanoparticles to Hollow Capsids and Their Superstructures
2017
| openaire: EC/FP7/291364/EU//MIMEFUN The synthesis and spontaneous, reversible supracolloidal hydrogen bond-driven self-assembly of cobalt nanoparticles (CoNPs) into hollow shell-like capsids and their directed assembly to higher order superstructures is presented. CoNPs and capsids form in one step upon mixing dicobalt octacarbonyl (Co2CO8) and p-aminobenzoic acid (pABA) in 1,2-dichlorobenzene using heating-up synthesis without additional catalysts or stabilizers. This leads to pABA capped CoNPs (core ca. 5nm) with a narrow size distribution. They spontaneously assemble into tunable spherical capsids (d≈50-200nm) with a few-layered shells, as driven by inter-nanoparticle hydrogen bonds th…
Cell uptake enhancement of folate targeted polymer coated magnetic nanoparticles.
2013
Dual targeted drug delivery systems represent a potential platform for developing efficient vector to tumor sites. In this study we evaluated a folate- and magnetic-targeted nanocarriers based on 10 nm iron oxide nanodomais coated with the properly synthesized and characterized folic acid (FA)-functionalized amphiphilic copolymer PHEA-PLA-PEG-FA. FA was chemically conjugated to one end of diamino-polyethylene glycol of 2000 Da, in order to ensure its exposition on the polymer coated magnetic nanoparticles (MNPs-FA). The prepared nanoparticles have been exhaustively characterized by different methods, including DLS, SEM, FT-IR and magnetic measurements. Magnetic nanoparticles showed dimensio…
Hybrid magnetic materials formed by ferritin intercalated into a layered double hydroxide
2008
A hybrid magnetic material formed by ferritin intercalated into a layered double hydroxide (LDH) of Mg and Al (Mg/Al molar ratio 2) is prepared and characterized through powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, electron probe microanalysis (EPMA) and high resolution transmission electron microscopy (HRTEM). One observes an enhancement in the thermal stability of the ferritin molecules when they are inserted in the layered material. Magnetic measurements of the hybrid material exhibit the typical superparamagnetic behaviour of the ferritin molecule. On the other hand, the intercalation of ferritin into the LDH guarante…
Langmuir monolayers and Langmuir–Blodgett films of ferritin prepared by using a surfactant mixture of eicosylamine (EA) and methyl stearate (SME)
2007
Abstract Magnetic Langmuir–Blodgett films of ferritin have been prepared by using the adsorption properties of a 1/4 mixed monolayer of eicosylamine (EA) and methyl stearate (SME). BAM images show that a more homogeneous distribution of ferritin at the air–water interface is achieved by using this mixture of surfactants instead of the DODA/SME mixed matrix of a previous work. Transfer of the monolayer onto different substrates allowed the preparation of multilayer LB films. Infrared and UV–Vis spectroscopies indicate that ferritin molecules are incorporated within the LB films. Furthermore, UV–Vis spectroscopy measurements reveal that the amount of ferritin incorporated into these LB film h…
Spectroscopic Signature of the Superparamagnetic Transition and Surface Spin Disorder in CoFe2O4 Nanoparticles
2012
Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of CoFe(2)O(4) nanoparticles and compared our results to trends in the coercivity over the same size range and to the response of the bulk material. Remarkably, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm. A spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the magnetically disordered shell thickness, which increases from 0.4 nm i…
Dysprosium-Based Ionic Liquid Crystals: Thermal, Structural, Photo- and Magnetophysical Properties
2009
[C12mim]3[DyBr6] (C12mim = 1-dodecyl-3-methylimidazolium) represents a new material with interesting luminescent behavior as well as mesomorphic and magnetic properties. The compound was found to show thermotropic liquid crystalline behavior and forms smectic mesophases which were investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry. The emission color of [C12mim]3[DyBr6] can be tuned from white to orange-yellow by the choice of the excitation wavelength. Sample excitation with λex = 366 nm leads to the blue-whitish luminescence from the imidazolium cation itself. With λex = 254 nm the common Dy(III) emission is observed which mainly arises from the …
Polymeric Nanocarriers for Magnetic Targeted Drug Delivery: Preparation, Characterization, and in Vitro and in Vivo Evaluation
2013
In this paper the preparation of magnetic nano- carriers (MNCs), containing superparamagnetic domains, is reported, useful as potential magnetically targeted drug delivery systems. The preparation of MNCs was performed by using the PHEA-IB-p(BMA) graft copolymer as coating material through the homogenization−solvent evaporation method. Magnetic and nonmagnetic nanocarriers containing flutamide (FLU-MNCs) were prepared. The prepared nanocarriers have been exhaustively characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and magnetic measurements. Biological evaluation was performed by in vitro cytotoxicity and cell uptake tests and in vivo biodistribution …
Quantification of pedogenic particles masked by geogenic magnetic fraction
2021
AbstractPedogenic magnetic fraction in soils is attributed to fine-grained particles, i.e. superparamagnetic grains. In the case of a strongly magnetic geogenic fraction, pedogenic magnetic contribution is hard to detect. To the best of our knowledge, detailed research into the masking of pedogenic superparamagnetic grains and quantification of this effect has not yet been carried out. The principal aim of our research is to quantify the influence of coarse-grained ferrimagnetic fraction on the detection of the superparamagnetic grains. In order to describe the masking phenomenon, volume and frequency-dependent magnetic susceptibility were determined on a set of laboratory prepared samples …
Highly water-soluble magnetic iron oxide (Fe3O4) nanoparticles for drug delivery: enhanced in vitro therapeutic efficacy of doxorubicin and MION conj…
2013
We report a simple one step protocol for the preparation of fairly monodisperse and highly water-soluble magnetic iron oxide nanoparticles (MIONs) through a co-precipitation method using a novel multifunctional, biocompatible and water-soluble polymer ligand dodecanethiol–polymethacrylic acid (DDT–PMAA). DDT–PMAA owing to its several intrinsic properties, not only efficiently controls the size of the MIONs but also gives them excellent water solubility, long time stability against aggregation and oxidation, biocompatibility and multifunctional surface rich in thioether and carboxylic acid groups. The molecular weight and concentration of the polymer ligand were optimized to produce ultrasma…