Monodisperse Magnetite Nanoparticles Research Articles

Design and synthesis of biologically inspired biocompatible various polymeric magnetic nanoparticles for imaging and biomedical applications

Highly monodispersed magnetite nanoparticles with controlled particle size and surface coatings have been successfully synthesized as a model system to investigate the effect of the surface coating on the magnetic properties. In this study, iron oxide (Fe3O4) magnetic nanoparticles (MNPs) were modified with polyethylene glycol (PEG), polyvinyl alcohol (PVA), poly(N-vinyl pyrrolidone) (PVP) and oleic acid coatings, templates and stabilizers to synthesise Fe3O4 nanoparticles through the co-precipitation method. The resultant magnetic nanoparticles were characterized by TEM, FTIR, XRD, Zeta, VSM and NMR analyses to evaluate their physical and magnetic properties. The obtained Fe3O4, Fe3O4 @PEG400, Fe3O4 @PEG6000, Fe3O4 @PVP, Fe3O4 @PVA and Fe3O4 @oleic acid MNPs showed T2 contrast performance with r2 relaxivities of 60.62, 37.37, 1502.40, 1641.99, 4875.63 and 114.01 mM s-1. The cell viability assay exhibited good biocompatibility.

A facile one-pot synthesis of phyto-conjugate superparamagnetic magnetite nanoparticles for the rapid removal of hexavalent chromium from water bodies

Sustainable and economical strategies for producing efficacious adsorbent systems for the rapid removal of hazardous Cr(VI) have recently gained research attention. This study employs the aqueous extract of Chromolaena odorata flowers as a green reductant and capping agent for the synthesis of Chromolaena odorata-derived magnetite nanoparticles (CMNs). The method yielded relatively monodispersed and small superparamagnetic magnetite nanoparticles with an average particle size of 3.14±0.25 nm. At an optimum pH of 2, CMNs enabled rapid removal of Cr(VI) and its subsequent reduction to Cr(III) in under 10 minutes. The maximum adsorption capacity recorded was 173.12 mg g−1. The adsorption conformed to Langmuir adsorption isotherm and followed pseudo first order kinetics. The strong magnetic nature of the adsorbent facilitated easy separation and recycling after adsorption. The present work provides insights into the use of aggressive weeds for the phytogenic development of eco-compatible adsorbents for rapid chromium reduction and removal.

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals.

In this study, a comprehensive characterization of iron oxide nanoparticles synthesized by using a simple one-pot thermal decomposition route is presented. In order to obtain monodisperse magnetite nanoparticles with high saturation magnetization, close to the bulk material, the molar ratios between the starting materials (solvents, reducing agents, and surfactants) were varied. Two out of nine conditions investigated in this study resulted in monodisperse iron oxide nanoparticles with high saturation magnetization (90 and 93% of bulk magnetite). The X-ray diffraction analyses along with the inspection of the lattice structure through transmission electron micrographs revealed that the main cause of the reduced magnetization in the other seven samples is likely due to the presence of distortion and microstrain in the particles. Although the thermogravimetric analysis, Raman and Fourier transform infrared spectroscopies confirmed the presence of covalently bonded oleic acid on the surface of all the samples, the particles with higher polydispersity and the lowest surface coating molecules showed the lowest saturation magnetization. Based on the observed results, it could be speculated that the changes in the kinetics of the reactions, induced by varying the molar ratio of the starting chemicals, can lead to the production of the particles with higher polydispersity and/or lattice deformation in their crystal structures. Finally, it was concluded that the experimental conditions for obtaining high-quality iron oxide nanoparticles, particularly the molar ratios and the heating profile, should not be chosen independently; for any specific molar ratio, there may exist a specific heating profile or vice versa. Because this synthetic consideration has rarely been reported in the literature, our results can give insights into the design of iron oxide nanoparticles with high saturation magnetization for different applications.

Temperature dependence of the magnetic interactions taking place in monodisperse magnetite nanoparticles having different morphologies

We report on the temperature dependence of the interactions present in single crystal magnetite nanoparticles having octahedral and spherical morphologies. From our results we conclude that the inter-particle interactions are, at all temperatures and in both octahedral and spherical nanoparticles, demagnetizing in nature. These interactions are not describable in terms of a mean field but local and linked to the poles present at the surfaces of the particles and particles clusters. In both samples, the peak on the field dependence of the interactions has an associated maximum that decreases in magnitude with an increase of the measuring temperature. Also, that peak gets narrower when the temperature is increased. The high order multipolar moments of the octahedral nanoparticles, originated by the fact that their morphology includes the presence of edges an dihedra, is detectable in the larger field range in which the interactions are observable in these samples in comparison with that corresponding to the spherical nanoparticles, exhibiting close-to-dipolar moments.

Synthesis of single‐phase and controlled monodisperse magnetite Fe3O4 nanoparticles

AbstractWe report a simple solvothermal method for the synthesis of monodisperse magnetite nanoparticles with a controlled particle size within the range of 40 to 200 nm from available and inexpensive single iron precursor (FeCl3) and, as co‐capping agents, sodium acetate and ethylene diamine. The particle size can be easily controlled by the reaction time of synthesis. Transmission electron microscopy, x‐ray diffraction, Fourier transform infrared spectroscopy, and x‐ray photoelectron spectroscopy techniques were used to investigate the obtained particles. The results revealed that the resulting iron oxide particles exhibit a single magnetite Fe3O4 phase and high stability in air even for four months. The high air stability of these magnetite could be due to the surfactant capped on the particle surface. This method of synthesis has some advantages including simplicity, high product quality, and acceptable reproducibility. Therefore, the magnetite particles can be used for different applications such as in catalysis and drug delivery.

Characterization of Superparamagnetic/Monodisperse PEG-Coated Magnetite Nanoparticles Sonochemically Prepared from the Hematite Ore for Cd(II) Removal from Aqueous Solutions

In this study, a novel sonochemically synthetic process of superparamagnetic and monodisperse magnetite nanoparticles from the Egyptian hematite ore has been done. Then the synthesized magnetite nanoparticles were subjected to surface modification through coating by polyethylene glycol to obtain stabilized and biocompatible magnetic nanoparticles (PEG-MN). The synthesized PEG-MN nanoparticles were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XRF), vibrating sample magnetometer (VSM), infrared spectroscopy (FT-IR), adsorption of nitrogen (BET method), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy. The results showed that the synthesized PEG-MN nanoparticles have an average crystalline size of 12 nm and 69.6% of iron oxide (Fe3O4) in the sample with a specific surface area of 219 m2/g. The magnetic hysteresis curve revealed that the synthesized PEG-MN nanoparticles exhibit a superparamagnetic behavior at room temperature with a saturation magnetization of 39.370 emu/g. While the morphology of the synthesized PEG-MN nanoparticles displayed a spherical shape and well-PEG coating of the magnetite particles as well as a perfect monodispersity of the particles. The reactivity of the PEG-MN nanoparticles was examined for adsorption of the cadmium ion Cd(II) from aqueous solutions. The maximum adsorption capacity of the PEG-MN nanoparticles was found to be 0.452 mg/g. The adsorption process is well fitted by the pseudo-second-order kinetic model, and the adsorption efficiency of Cd(II) was found to be 52% suggesting that the synthesized PEG-MN nanoparticles are an effective and promising tool for the removal of the selected metal.

Highly monodisperse and colloidal stable of L-serine capped magnetite nanoparticles synthesized via sonochemistry assisted co-precipitation method

Highly monodispersed magnetite nanoparticles (MNPs) were successfully prepared by means of a sonochemistry-assisted co-precipitation method in the presence of L-serine (L-ser). In order to understand the effect of the L-serine on the development of nanoparticles, various concentrations (0, 1, 3 and 5 mmol) of L-ser were employed. In this study, a conventional co-precipitation method was also performed to prepare MNPs (denoted as MNP-1) as a comparison. The MNPs prepared via sonochemistry-assisted co-precipitation method (MNP-2) have better crystallinity and morphological uniformity than MNP-1, which were observed by XRD and TEM measurements, respectively. Synergistically, the introduction of L-ser as a capping agent during the ultrasound irradiation significantly improved the particle size monodispersity and colloidal stability of MNP-2. In addition, the magnetic sensitivity of MNP-2 (Ms = 57.12 emu g−1) was not altered significantly even with the addition of 5 mmol of L-ser (Ms = 48.34 emu g−1). This investigation shows that the L-ser acts not only as a capping agent to improve the colloidal stability of nanoparticles but also as a particle size controlling agent.

Investigations of the effective parameters on the synthesis of monodispersed magnetic Fe3O4 by solvothermal method for biomedical applications

Monodispersed magnetite nanoparticles were obtained by investigating the different synthesis parameters of the solvothermal method. The morphology and chemical structure of the Fe3O4 nanoparticles were characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Dynamic Light Scattering (DLS) and Vibrating sample magnetometer (VSM). Results indicated that without the addition of water, it forms the minor phase of iron instead of magnetite. Furthermore, the size of nanoparticles is tunable in the range of 117.7 to 217.6 nm by changing the amounts of water, PSSMA and NaOH. The amount of PSSMA restricts the growth of the nanoparticles and narrow the size distribution and a hydrophilic surface was obtained. Synthesized magnetite nanoparticles were successfully conjugated with carbon dots. The resulting nanoparticles exhibited good fluorescence characteristics. Cytotoxicity tests confirmed that nanoparticles are non-toxic. Both magnetite and C-dots/Fe3O4 nanoparticles are good potential candidates for biomedical applications specifically for bioimaging and biosensing in the future.

Synthesis and Characterization of Tea Polyphenol–Coated Magnetite Nanoparticles for Hyperthermia Application

Tea polyphenol–coated magnetite nanoparticles were evaluated for hyperthermia application. Polyphenol extracted from the tea leaves was used as a reducing and capping agent for the synthesis of good-quality mono-dispersed magnetite nanoparticles from an iron hydroxide solution. The as-synthesized samples were found to be mostly single-phase magnetite (Fe3O4) with a small amount of hematite (α-Fe2O3) as a secondary phase. Tea polyphenol suppresses the amount of the secondary phase present in the samples. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transmission infrared spectrometry (FTIR), and vibration sample magnetometry (VSM) were used to investigate the properties of the samples. The Rietveld refinement technique was employed for the quantitative estimation of the secondary α-Fe2O3 phase along with the primary Fe3O4 phase from the XRD patterns. Absorption peaks at 1635/1615 cm−1 and 2950/2862 cm−1 due to the C=C bond and the C–H stretching vibration, respectively, bear the signature of polyphenol present in the samples. The average particle size of the particles was measured by TEM as 10 nm. Polyphenol coating enhances the value of the saturation magnetization (MS) of the iron oxide nanoparticles from 39 to 44 emu/g. The blocking temperature for coated and uncoated samples was estimated as 167 K and 195 K, respectively, which also confirms that samples are superparamagnetic at room temperature. Cytotoxicity of the nanoparticles was investigated using MTT assay on the L929 fibroblast cell line, and cell viability was found to increase for the coated sample. The specific absorption rate of polyphenol-coated nanoparticles in water was measured as 105 W/g for a sample concentration of 5 mg/ml in the AC magnetic field of 7.74 kA/m and frequency 337 kHz as compared to 66 W/g for the uncoated sample under the same conditions. The results demonstrate that the polyphenol coating enhances MS and biocompatibility of these nanoparticles which can be considered as a potential candidate for use as thermo seeds in hyperthermia application.

From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles

Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained.

Biogenic magnetite nanoparticles: A potent and environmentally benign agent for efficient removal of azo dyes and phenolic contaminants from water.

A comprehensive study was conducted toward the green and facile synthesis of biocompatible magnetite nanoparticles for the efficient removal of organic contaminants from water. The nanoparticles were synthesized using a modified co-precipitation method and functionalized by the taxane diterpenoids extracted from Taxus baccata L., and fully characterized using UV-vis spectroscopy, SEM, FTIR, VSM, and XRD. The synthesized monodisperse magnetite nanoparticles, with a narrow size distribution of less than 50 nm, displayed significant and stable magnetic activity without surface oxidation after several months. The batch experiments clearly indicated the efficient iron-catalyzed removal of Nile blue, methylene blue, methylene orange, and 4-nitrophenol for several cycles without significant loss of catalytic activity. The relevant kinetic data of the dyes removal reactions were fitted to a pseudo-first order model. Moreover, in vitro MTT assay revealed high biocompatibility of the nanoparticles with no significant toxicity on different human cell lines. The overall results indicated high potential of green synthesized, biocompatible magnetite nanoparticles for the environmental applications especially wastewater remediation.

Monodisperse magnetite nanoparticles with high sensitivity as MRI contrast agents

The preparation of monodisperse and biocompatible water-soluble super-paramagnetic iron oxide nanoparticles (SPIONs) with high sensitivity in Magnetic Resonance Imaging (MRI) represents a challenge for the development of contrast agents. Here we report the synthesis of highly monodisperse citric acid (CA) coated SPIONs with an average diameter of 9 nm and spherical shape, prepared through a suitably optimized coprecipitation method. CA-SPIONs show a high solubility and stability in aqueous medium. Imaging of CA-SPIONs aqueous suspensions was performed in a clinical 1.5-T MRI scanner and different clinical acquisition sequences were exploited. Results show that image contrast can be effectively improved when concentrations of SPIONs lower than 1 ppm are present, and that the echo time is the main parameter influencing the image contrast of SPION-loaded solutions. Moreover, we found that CA-SPIONs show a high value of transverse relaxivity of 128 L mmol -1 s -1 (higher than the commercial contrast agents). Our results are encouraging for the further development of clinical application of SPIONs in MRI, and can represent a starting point for the optimization of clinical imaging exploiting the contrast enhancement of such agents. Namely, it seems possible to achieve an optimal image contrast with low concentration of SPIONs; this could lead to a lower probability of side effects.

Size-dependent magnetic responsiveness of magnetite nanoparticles synthesised by co-precipitation and solvothermal methods

Abstract The dependence of the magnetic responsiveness on magnetite nanoparticle size has been studied. Monodisperse magnetite nanoparticles of 10 nm diameter were prepared by an ultrasonically enhanced co-precipitation procedure. A carboxyl-functionalised solvothermal approach was applied to synthesise magnetite nanoparticles with an average size of 30 nm. The particle sizes and their distribution have been determined by analysing TEM images and considering nanoparticle formation mechanisms. The magnetic characterisation revealed an inverse dependence between the magnetite nanoparticle size and its ability to respond to external magnetic fields, which was explained by the decrease of magnetic dipoles inside the tailing-away crystal of the magnetite nanoparticles. Negligible hysteresis with a small value of 5 Oe was found for the 10 nm nanoparticles, while the larger value of 80 Oe was determined for the 30 nm nanoparticles.

Combined Experimental and Theoretical Investigation of Heating Rate on Growth of Iron Oxide Nanoparticles

Thermal decomposition is a promising route for the synthesis of highly monodisperse magnetite nanoparticles. However, the apparent simplicity of the synthesis is counterbalanced by the complex interplay of the reagents with the reaction variables that determine the final particle size and dispersity. Here, we present a combined experimental and theoretical study on the influence of the heating rate on crystal growth, size, and monodispersity of iron oxide nanoparticles. We synthesized monodisperse nanoparticles with sizes varying from 6.3 to 27 nm simply by controlling the heating rate of the reaction. The nanoparticles show size-dependent superparamagnetic behavior. Using numerical calculations based on the classical nucleation theory and growth model, we identified the relative time scales associated with the heating rate and precursor-to-monomer (growth species) conversion rate as a decisive factor influencing the final size and dispersity of the nanoparticles.

Synthesis and Characterization of Monodisperse Magnetite Nanoparticles by Hydrothermal Method

Monodisperse nanoparticles are materials that are not agglomerate. The good characteristic of these materials is the dispersity in water, so they can better react with target pollutants. Accordingly, in this work, the monodisperse magnetite nanoparticles with the superparamagnetic property were synthesized and characterized. The hydrothermal method with the iron compound and polymer as precursors was conducted. The magnetic nanoparticles were characterized by several techniques including X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, and vibrating sample magnetometer. The saturation magnetization (Ms) value, the coercivity (Hc), and the retentivity (Mr) were measured to demonstrate the paramagnetic behavior of the monodisperse magnetite nanoparticles. The results showed that the Fe3O4 nanoparticle were obtained at 200 °C for 16 h. The particles are monodispersed with the size approximately in the range of 60 - 250 nm as confirmed by FE-SEM and TEM images. These are the single grain and had the spherical shape similar to a blackberry. The saturation magnetization of 17.287 emu/g and ratio of retentivity to saturation magnetization (Mr/Ms) characterized the squareness of the hysteresis loops was 0.03653. It can be indicated that the Fe3O4 nanoparticles had superparamagnetic behavior. This property of Fe3O4 nanoparticles can draw pollutants to absorb on the surface of these nanomaterials. Then adsorbed pollutants can be easily removed by separating the Fe3O4 materials from water. This technique can be applied further in water treatment and pollutant removal.

Lead (Pb2+) adsorption by monodispersed magnetite nanoparticles: Surface analysis and effects of solution chemistry

Monodispersed magnetite nanoparticles [Fe3O4-NPs] were synthesized by chemical co-precipitation using ferrous and ferric chloride as iron precursors. The composition, surface properties and morphology were investigated using X-ray powder diffraction, transmission electron microscopy, dynamic light scattering, scanning electron microscopy and Fourier transform infrared spectroscopy. Synthesized magnetite nanoparticles have zeta potential of +22.0mV and an energy bandgap of 2.2eV. These NPs were used for aqueous Pb2+ removal at different initial pHs, equilibrium time, temperature and adsorbent/adsorbate concentrations. Pb2+ adsorption was increased with rise in solution pH. Almost 100% Pb2+ removal was achieved [at magnetite NPs dose: 0.2g/L; Pb2+ concentration: 50mg/L; pH 5.0; shaking speed: 200rpm; temperature: 25°C and equilibrium time: 30min]. Pseudo-first and pseudo-second order kinetic equations were applied to evaluate the kinetic data. Pseudo-second-order rate equation better fitted the data. Spent NPs were regenerated using 0.005M HNO3. Exhausted magnetite NPs were successfully recovered from aqueous system using a simple magnet. These magnetite NPs can also be used for Pb2+ removal from waters having high concentration of suspended particles.

Controlled synthesis of monodisperse magnetite nanoparticles for hyperthermia-based treatments

Monodisperse magnetite nanospheres with hollow interior and porous shell structure were synthesized through one-pot solvothermal process. The chemical conversions of the Fe (III) compounds to generate Fe3O4 simultaneously coupled with the Ostwald ripening process within the magnetite spheres were considered as underlying mechanism for evolution of the Fe3O4 porous/hollow nanostructure. The morphology of Fe3O4 nanoparticles could be controlled by adjusting the conditions of process variables. We investigated their potential in hyperthermia-based treatments, using an alternative magnetic field. Our study revealed that higher applied frequency resulted in the higher heat generation and thus faster temperature growth. The hyperthermia efficiency of the Fe3O4 nanoparticles generally depended on particle structures and magnetic properties. The Fe3O4 porous/hollow nanoparticles also exhibited an excellent heat generation for several continuous cycles of applied field for a long time.

Monodisperse magnetite (Fe3O4) nanoparticles modified with water soluble polymers for the diagnosis of breast cancer by MRI method

In this study, magnetic nanoparticles (MNPs) were synthesized via co-precipitation method. To enhance the biocompatibility and colloidal stability of the synthesized nanoparticles, they were modified with carboxyl functionalized PEG via dopamine (DPA) linker. Both modified and unmodified Fe3O4 nanoparticles exhibited super paramagnetic behavior (particle size below 20nm). The saturation magnetization (Ms) of PEGdiacid-modified Fe3O4 was 45emu/g, which was less than the unmodified Fe3O4 nanoparticles (70emu/g). This difference indicated that PEGdiacid polymer was immobilized on the surface of Fe3O4 nanoparticles successfully. To evaluate the efficiency of the resulting nanoparticles as contrast agents for magnetic resonance imaging (MRI), different concentration of MNPs and different value of echo time TE were investigated. The results showed that by increasing the concentration of the nanoparticles, transverse relaxation time (T2) decreased, which subsequently resulted in MR signal enhancement. T2-weighted MR images of the different concentration of MNPs in different value of echo time TE indicated that MR signal intensity increased with increase in TE value up to 66 and then remained constant. The cytotoxicity effect of the modified and unmodified nanoparticles was evaluated in three different concentrations (12, 60 and 312mgl−1) on MDA-MB-231 cancer cells for 24 and 48h. In both tested time (24 and 48h) for all three samples, the modified nanoparticles had long life time than unmodified nanoparticles. Cellular uptake of modified MNPs was 80% and reduced to 9% by the unmodified MNPs.

Simple and novel strategies to achieve shape and size control of magnetite nanoparticles intended for biomedical applications

Monodisperse magnetite nanoparticles (MNPs) with controlled sizes and shapes were prepared. The synthesis was carried out by traditional and inverted co-precipitation method with some modifications such as presence of visible light, room temperature and absence of inert atmosphere. Sodium dodecyl sulphate (SDS) was employed as stabilizer. The mentioned experimental parameters were conveniently adjusted to obtain suitable MNPs, to be efficiently employed in biomedical applications. In particular the size, shape, surface charge and magnetic properties were evaluated. MNPs were thoroughly characterized. From characterization data, it emerged that the inverted co-precipitation in presence of visible light rendered mainly nanorods. Modifying the SDS concentration the shape was tuned from nanorods to nanospheres and finally, at higher concentrations, nanocubes were obtained. All prepared formulations resulted hydrophilic. This property was justified in terms of the stabilization mechanism of SDS.Stability of MNPs aqueous dispersions was evaluated regarding to the variation of hydrodynamic diameter as a function of the time. In this regard, all the formulations resulted stable during, at least, 30 days. The prepared nanosystems exhibited satisfactory magnetic properties with saturation magnetization slightly lower than raw magnetite.The combination of size, shape, surface charge, hidrophilicity and magnetic behaviour make the magnetic nanosystems here obtained highly suitable and promising to diagnostic and therapeutic applications.

Monodisperse magnetite nanoparticles with nearly ideal saturation magnetization

We present a scalable thermolysis and high temperature oxidation procedure for synthesizing monodisperse magnetite nanoparticles with saturation magnetization of up to 80 emu g−1 (412 kA m−1), 92% of bulk magnetite.