Core-shell Iron Oxide Nanoparticles Research Articles

Hybrid response surface methodology-genetic algorithm optimization of ultrasound-assisted transesterification of waste oil catalysed by immobilized lipase on mesoporous silica/iron oxide magnetic core-shell nanoparticles

The production of biodiesel by transesterification of waste cooking oil (WCO) to partially substitute petroleum diesel is one of the measures for solving the twin problems of environment pollution and energy demand. An environmentally benign process for the enzymatic transesterification using immobilized lipase has attracted considerable attention for biodiesel production. Here, a superparamagnetic, high surface area substrate for lipase immobilization is evaluated. These immobilization substrates are composed of mesoporous silica/superparamagnetic iron oxide core-shell nanoparticles. The effects of methanol ratio to WCO, lipase concentration, water content and reaction time on the synthesis of biodiesel were analysed by utilizing the response surface methodology (RSM). A quadratic response surface equation for calculating fatty acid methyl ester (FAME) content as the objective function was established based on experimental data obtained in accordance with the central composite design. The RSM-based model was then used as the fitness function for genetic algorithm (GA) to optimize its input space. Hybrid RSM-GA predicted the maximum FAME content (91%) at the optimum level of medium variables: methanol ratio to WCO, 4.34; lipase content, 43.6%; water content, 10.22%; and reaction time, 6 h. Moreover, the immobilized lipase could be used for four times without considerable loss of the activity.

Polyhedral iron oxide core–shell nanoparticles in a biodegradable polymeric matrix: preparation, characterization and application in magnetic particle hyperthermia and drug delivery

Polyhedral magnetic iron oxide nanocrystals with multiple facets have been embedded in biocompatible and biodegradable polymeric matrices in order to study their structural, magnetic features and alternating-current (AC) magnetic heating efficiency. The encapsulation of iron oxide nanoparticles into a polymer matrix was confirmed by transmission electron microscopy and further corroborated by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). HAADF-STEM tomography proved that the iron oxide nanocrystals consist of well-defined polyhedral structures with multiple facets. The magnetic features were found to be in good agreement with the structural and morphological features and are maintained even after encapsulation. Furthermore, the magnetic nanoparticles inside these matrices may be considered as good candidates for biomedical applications in hyperthermia treatments because of their high heating capacity exhibited under an alternating magnetic field. The anticancer Taxol drug was encapsulated in these nanoparticles and its physical state and release rate at 37 and 42 °C was studied.

How hollow structures form from crystalline iron–iron oxide core–shell nanoparticles in the electron beam

Here, we report the effect of oleylamine (OLA) stabilizing molecules on the stability of iron-iron oxide core-shell nanoparticles in the electron beam. The presence of excess OLA (>50 wt%) induces the structural transformation in the highly crystalline, core-shell structures to form hollow iron oxide nanoparticles after 120 s of electron beam exposure.

One-pot synthesis of water soluble iron nanoparticles using rationally-designed peptides and ligand release

Herein we report the rational design of new phosphopeptides for control of nucleation, growth and aggregation of water-soluble, superparamagnetic iron-iron oxide core-shell nanoparticles. The use of the designed peptides enables a one-pot synthesis that avoids utilizing unstable or toxic iron precursors, organic solvents, and the need for exchange of capping agent after synthesis of the NPs.

ChemInform Abstract: Iron—Iron Oxide Core—Shell Nanoparticles Are Active and Magnetically Recyclable Olefin and Alkyne Hydrogenation Catalysts in Protic and Aqueous Media.

AbstractThe catalyst shows selectivity towards the less activated double bonds and tolerates the presence of air and water.

Targeted dual-contrast T1- and T2-weighted magnetic resonance imaging of tumors using multifunctional gadolinium-labeled superparamagnetic iron oxide nanoparticles

Development of a multifunctional nanoparticle (NP) system allowing for dual-contrast T 1- and T 2-weighted targeted magnetic resonance (MR) imaging of tumors could significantly improve the diagnosis accuracy. In this study, superparamagnetic silica-coated iron oxide core-shell nanoparticles (Fe 3O 4@SiO 2 NPs) with a diameter of approximately 21 nm were synthesized via a thermal decomposition approach and were aminated through silanization. The amine-functionalized Fe 3O 4@SiO 2 NPs enabled the covalent conjugation of a paramagnetic gadolinium complex (Gd-DTPA, DTPA: diethylenetriamine pentaacetic acid) and an arginine-glycine-aspartic acid (RGD) peptide as a targeting ligand onto their surface. The formed Fe 3O 4@SiO 2(Gd-DTPA)-RGD NPs are water-dispersible, stable, and biocompatible as confirmed by MTT cell viability assay. Relaxivity measurements show that they have a T 1 relaxivity ( r 1) of 4.2 m m −1 s −1 and T 2 relaxivity ( r 2) of 17.4 m m −1 s −1 at the Gd/Fe molar ratio of 0.3:1, suggesting a possibility to use them as both T 1 positive and T 2 negative contrast agents. In vitro and in vivo MR imaging experiments show that the developed multifunctional Fe 3O 4@SiO 2(Gd-DTPA)-RGD NPs enable targeted dual-contrast T 1- and T 2-weighted MR imaging of tumor cells over-expressing high-affinity α vβ 3 integrin in vitro and in vivo. Our results clearly indicate that the approach to forming multifunctional Fe 3O 4@SiO 2(Gd-DTPA)-RGD NPs could be extended for fabricating other biologically active NPs for T 1- and T 2-weighted MR imaging of other biological systems with high accuracy.

Increase in the Curie temperature and magnetic anisotropy in FePd/Pt–iron oxide core-shell nanoparticles

Partially oxidized fcc FePd and FePt nanoparticles with mean diameters of 5 and 3 nm, respectively, were synthesized by a reverse micelle polyol process. In situ measurements of magnetic and structural properties during annealing showed a large increase in the magnetocrystalline anisotropy and in the Curie temperature of the nanoparticles due to (i) a phase transition from A1 to L10 and (ii) a simultaneous phase separation between a metallic core and an iron oxide shell. These occurred at 675 K in the FePd nanoparticles and at above 850 K for the FePt. The Curie temperature of the nanoparticles was found to be about 850 K, an increase of more than 100 K from the bulk L10 phase. The ferromagnetic resonance results are discussed and compared with a phenomenological model that makes it possible to estimate the magnetocrystalline anisotropy as 1.6×105 and 1.5×106 J m−3 in FePd and FePt, respectively. Exchange coupling between the core and the shell explains both the high magnetocrystalline anisotropy of the core and the high Curie temperature of the shell.

Simultaneous magnetically directed drug convection and MR imaging

Superparamagnetic iron oxide nanoparticles (IO NPs) are of interest for theirusefulness in biomedical applications. In this work, we have synthesized iron oxidenanocomposites surface-modified with different biocompatible polymers. Bovine serumalbumin (BSA) was physisorbed onto these IO NPs along with an excipient duringfreeze-drying. The mass transport of the protein attached to the iron oxide core–shellnanoparticles (IO cs-NPs) under a gradient magnetic field of an MRI instrument wasobserved in vitro and in an egg as a model system for a biological fluid. Fromthe in vitro experiments in agarose gels, it was observed that the protein getsseparated from the core during mass transport for some cs-IO, but co-migrationwas observed for PEG-modified IO cs-NPs. These experiments demonstratedproof-of-concept for the use of IO cs-NPs in magnetically directed drug convection.

Synthesis of magnetic nanocomposites and alloys from platinum–iron oxide core–shellnanoparticles

This paper presents a systematic study on the generation of ironplatinum-containing magnetic nanocomposites and alloys fromPt@Fe2O3 core–shell nanoparticle precursors. These core–shell nanoparticles weremade using a sequential synthetic approach. They could form FePt alloysand alloy-containing nanocomposites through a solid-state reaction at>400 °C. The chemical compositions of FePt alloys were controllable by usingPt@Fe2O3 core–shell nanoparticles that had the designed Pt core diameter and iron oxide shell thickness.We show that face-centred tetragonal (fct) FePt@Fe core–shell nanoparticles could be made fromPt@Fe2O3 core–shell nanoparticles with 5% hydrogen in argon(v/v). Furthermore, various FePt alloys and alloy-containing nanocomposites includingmetastable intermediate phases could be obtained. The materials were characterized byhigh resolution scanning transmission electron microscopy (HR-STEM), energy dispersivex-ray (EDX) spectroscopy, powder x-ray diffraction (PXRD), parallel electron energy lossspectroscopy (PEELS), and superconducting quantum interference device (SQUID)magnetometry. These materials could have potential applications as permanent hardmagnets and data storage media.

Iron–iron oxide core–shell nanoparticles synthesized by laser pyrolysis followed by superficial oxidation

Iron-based core–shell nanostructures were synthesized by laser pyrolysis in a two-steps procedure. In a first step, using a cross-flow configuration, the laser radiation was heating a gas phase mixture containing iron pentacarbonyl (vapors) entrained by an ethylene flow, which plays also the role of an energy transfer agent. Secondly, a carefully controlled in situ passivation of the freshly formed pyrophoric iron nanoparticles created a protective iron oxide shell. The produced nanoparticles (22 nm size diameters) with core–shell features were analyzed by TEM, XRD, SAED and Raman spectroscopy. Majoritary iron and gamma iron oxide/magnetite and minoritary carbon phases were identified. In laser pyrolysis experiments in which the reaction temperature was increased, the catalyzed homogeneous nucleation and growth of carbon nanotubes in the gas phase was observed and is presented here for the first time.

Fabrication of Magnetic FePt Patterns from Langmuir–Blodgett Films of Platinum–Iron Oxide Core–Shell Nanoparticles

Fabrication of Magnetic FePt Patterns from Langmuir–Blodgett Films of Platinum–Iron Oxide Core–Shell Nanoparticles