Levent Colak

Chemically synthesized FePt nanoparticles with controlled particle size, shape and composition

Monodisperse Fe-Pt nanoparticles have been prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] and reduction of platinum acetylacetonate [Pt(acac)2] with dibenzyl ether in the presence of oleic acid and oleyl amine. The particle composition was adjusted by changing the Fe(CO)5/Pt(acac)2 molar ratio while fixing the Pt(acac)2 amount. The size of FePt nanoparticles was tuned by controlling the injection temperature of the iron precursor. The low injection temperature of precursors and the usage of surfactants as a reaction solvent, together with a slow heating to a low refluxing temperature, were found to be the key parameters for the formation of cubic nanoparticles. Nanorods were formed by simply adjusting the injection time of the surfactants. The as-made nanoparticles had a low coercivity, which was increased to 7 kOe when annealed at 800 degrees C for 1 h.

Development of heparin-coated magnetic nanoparticles for targeted drug delivery applications

We have designed a potential drug delivery system by combining low-molecular-weight heparin to iron oxide magnetic nanoparticles with an average size of 20 nm. The particles were synthesized by the NaBH4 reduction of FeCl2 and then coated with poly-L-lysine. Heparin was noncovalently conjugated on these nanoparticles via the interactions between the negatively charged sulfate and carboxylate groups of heparin and the positively charged amine group of poly-L-lysine. The nanoparticles were examined by using transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and zeta potential measurements. The data provide direct evidence that the heparin was immobilized at the surface of poly-L-lysine-coated iron oxide nanoparticles. Magnetic measurements revealed the particles are ferromagnetic with a saturation magnetization of 31 emu/g.

Direct chemical synthesis of L10 FePt nanoparticles

Ordered faced-centered tetragonal (fct) FePt nanoparticles were successfully synthesized by a chemical method using presynthesized Au nanoparticles as the “catalyst.” The reaction temperature was also studied and it seems that there is an optimum value of 360 °C where the fct structure is formed. The particles have a mean diameter of 3.5–15 nm and the x-ray diffraction patterns exhibited (001) and (110), which signified the tetragonal phase formation. Room temperature magnetic hysteresis loops show that the FePt particles have coercive fields between 0.68 and 2.8 kOe.

Metallic iron-based nanoparticles for biomedical applications

This study is focused on the fabrication and characterization of core-shell structured iron/iron-oxide nanoparticles for potential use in biomedical applications. In particular, we have investigated the effect of Pt seeding and the injection temperature of Fe(CO)5 precursor on the particles morphology and magnetic properties. Injection of the iron precursor at low temperature led to a mixture of core-shell structured particles and separate Fe-oxide particles. Whereas, injection at high temperatures led to only core-shell nanoparticles without any separate iron oxides. The importance of the use of Pt(acac)2 to achieve more uniform and oxide free particles is investigated in detail.

Array formation and size effects in chemically synthesized FePt nanoparticles

Monodisperse FePt nanoparticles (NP’s) have been synthesized by reduction of platinum acetylacetonate [Pt(acac)2] followed by thermal decomposition of iron pentacarbonyl [Fe(CO)5] in the presence of oleic acid (OA) and oleyl amine (OY) as surfactants at a low reaction temperature. Particle size is controlled by the injection temperature of Fe(CO)5. The effect of particle size on the blocking temperature has been investigated for nanoparticles with sizes of 3.0 and 6.0nm. The interparticle spacing is varied by changing the addition time of the OA and OY. Well-aligned mono- and multi-layered hexagonal-closed-packed (hcp) to square lattice nanostructures are formed for 5nm FePt NP’s. Surfactant layer thickness, ⟨L⟩ to metal core radius R (⟨L⟩∕R) ratios of 0.46 and 0.60 are evaluated for the monolayer of hexagonal-closed-packed and square lattice array structures, respectively. For hcp arrays bilayer and trilayer structures are also observed. Subjecting the NP’s to thermal processing at 800°C results in a tra...

Water Dispersible Fe/Fe-Oxide Core-Shell Structured Nanoparticles for Potential Biomedical Applications

In this paper, we report the synthesis and characterization of water dispersible core-shell structured Fe/Fe-oxide with average size 13 plusmn1.4 nm and Fe-oxide nanoparticles. Unlike the previously reported different approaches, both types of particles can be synthesized by following the same route with a small variation in the Fe(CO)5 molar concentration and oxygen free environments. The oleate/oleylamine coated nanoparticles were surface modified with tetra-methyl-ammonium-hydroxide (TMAOH) to make them water dispersible. TGA analysis provided direct evidence that TMAOH adds to the surface of the oleic acid and oleylamine coated particles making them well disperse and stable in water as is suggested from the zeta potential measurements also.

Synthesis of Biocompatible Magnetic Iron Oxide (γ-Fe 2 O 3 and Fe 3 O 4 ) Nanoparticles by a Modified Polyol Process for Biomedical Applications

Highly crystalline superparamagnetic Fe 3 O 4 nanoparticles coated by poly-vinylpyrrolidone (PVP) were prepared by simultaneous thermal decomposition of ferrous and ferric inorganic salts in polyethylene glycol (PEG) with molecular weight 200. The magnetic particles have a diameter in the range of 8-15 nm, and after exchange with citric acid diammonium salt, they transform into very stable super hydrophilic colloidal solutions. The presence of magnetite phase was confirmed using powder X-rays diffraction (XRD) and Mossbauer spectroscopy, while thermogravimetric analysis and FT-IR spectroscopy confirmed the presence of PVP or citrate anions on the nanoparticles surface. The magnetic properties revealed superparamagnetic behavior, with the composite material showing a saturation magnetization up to 57 emu/g. The Fe 3 O 4 nanoparticles prepared by this modified polyol process are suitable for biomedical applications because of the biocompatibility of citrate anions. Magnetic hyperthermia experiments in neutral water solutions shows that the particles induce fast heating rates with specific absorption rate (SAR) values which reached 57.53 W/gFe, when the concentration of iron is 11.2 mgFe/ml.

Structural and Magnetic Properties of Chemically Synthesized FexPt100-x Nanoparticles with Controlled Particle Size and Shape

FexPt100-x nanoparticles were synthesized by thermal decomposition of iron pentacarbonyl and reduction of platinum acetylacetonate. The structural and magnetic properties of the nanoparticles with controlled particle size and shape were studied. The nanoparticles show superparamagnetic behavior. The particles also show hard magnetic properties with coercivity of more than 12 kOe after annealing. HRTEM and Mossbauer studies were carried out to investigate the microstructural development in annealed samples.