Synthesis Of FePt Nanoparticles Research Articles

Synthesis of FePt Nanoparticles by Photoreduction and Chemical Reduction in Poly(ethyleneimine).

Using poly(ethyleneimine) (PEI) polymer substrates, spherical FePt nanoparticles (NPs) with diameter <10 nm have been synthesized by photoreduction and chemical reduction in aqueous media at room temperature. In the photoreduction approach, PEvI acts as both the template into which the metal ions are coordinated and as a reductant when irradiated by ultraviolet light. In the chemical reduction method, PEI acts as only a template, with NaBH4 as the reductant. The as-prepared NPs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). Starting from the same precursor state and relative concentrations, the as-prepared NPs from both methods are spherical, crystalline solid solutions with a chemically disordered face-centered cubic (fcc) structure. The as-prepared NPs from both methods are superparamagnetic with some contribution from a ferromagnetic phase. The photoreduced NPs have broad size distribution of (5 ± 1.0 nm), an expanded lattice (3.913 Å), and relatively lower magnetic moment (0.02 emu/g) compared to the narrower size distribution (4 ± 0.7 nm), shortened lattice (3.890 Å), and a dominant moment (15 emu/g) of the chemically reduced NPs. The difference in the rate of particle formation apparently leads to a low efficiency of FePt NP formation via photoreduction compared to chemical reduction.

3D Microprinting of Iron Platinum Nanoparticle-Based Magnetic Mobile Microrobots.

Wireless magnetic microrobots are envisioned to revolutionize minimally invasive medicine. While many promising medical magnetic microrobots are proposed, the ones using hard magnetic materials are not mostly biocompatible, and the ones using biocompatible soft magnetic nanoparticles are magnetically very weak and, therefore, difficult to actuate. Thus, biocompatible hard magnetic micro/nanomaterials are essential toward easy-to-actuate and clinically viable 3D medical microrobots. To fill such crucial gap, this study proposes ferromagnetic and biocompatible iron platinum (FePt) nanoparticle-based 3D microprinting of microrobots using the two-photon polymerization technique. A modified one-pot synthesis method is presented for producing FePt nanoparticles in large volumes and 3D printing of helical microswimmers made from biocompatible trimethy- lolpropane ethoxylate triacrylate (PETA) polymer with embedded FePt nanoparticles. The 30 μm long helical magnetic microswimmers are able to swim at speeds of over five body lengths per second at 200 Hz, making them the fastest helical swimmer in the tens of micrometer length scale at the corresponding low- magnitude actuation fields of 5-10 mT. It is also experimentally in vitro verified that the synthesized FePt nanoparticles are biocompatible. Thus, such 3D-printed microrobots are biocompatible and easy to actuate toward creating clinically viable future medical microrobots.

Evolutions of microstructure and magnetic property of wet-chemical synthesized FePt nanoparticles assisted by high magnetic field

A high magnetic field up to 6 T was introduced into the wet-chemical process to synthesize FePt nanoparticles. The effects of high magnetic field on the composition, crystal structure, shape, size and magnetic property of FePt nanoparticles were studied. Under the high magnetic fields, the grain size of FePt nanoparticles refined, and the shape transformed from cube to truncated-cube and concave-cube to cube. However, the high magnetic fields show no significance effects on the composition and crystal structure of FePt nanoparticles. As a result, the magnetic properties of FePt nanoparticles were tuned by high magnetic fields. The coercivity at low-temperature (10 K) and the blocking temperature both decreased at 6 T. The results highlight the feasibility of applying an in-situ high magnetic fields to tune magnetic properties of the wet-chemical synthesized nanoparticles.

Influence of Particle Size on the Spin Pinning Effect in the fcc-FePt Nanoparticles

In this work, the Fe60Pt40 nanoparticles were synthesized through the chemical reduction method by using the Fe(CO)5 and the Pt(acac)2 as the metallic precursor. The particle size of the synthesized FePt nanoparticles was controlled by adjusting the reaction conditions involving of the Fe(CO)5-injecting temperature and the soak time of reaction. The structure, morphology, and magnetic properties of the synthesized FePt nanoparticles were characterized by XRD, TEM, and vibrating sample magnetometer (VSM), respectively. The synthesized nanoparticles exhibit uniform size and good dispersity. The magnetization behaviors indicate that the nanoparticles present the core-shell magnetic structure including the ferromagnetic core part and the spin-disorder shell part. There exists a spin pinning effect of the shell part on the core part. The increase of particle size weakens the spin pinning effect.

Effect of Heating and Cooling Rates in Annealing for Preparation of L10-FePt Nanoparticles on Si Substrate

In order to obtain highly ordered L10-FePt nanoparticles for hard disk drive applications, the L10-phase transformation of chemically synthesized FePt nanoparticles deposited on a naturally oxidized Si substrate was investigated using rapid thermal annealing. The heating and cooling rates during annealing were changed logarithmically with a constant annealing temperature (800°C) and holding time (10 min). Almost completely ordered L10-FePt nanoparticles were confirmed by grazing incidence X-ray diffraction measurements, irrespective of the heating and cooling rates, and the amount of the silicide changed in response to both. Nearly pure L10-FePt was obtained when rapid heating (more than 780 K/min) and rapid cooling (more than 290 K/min) were applied. L10-FePt degraded into Fe3Si and PtSi when the cooling rate was lower than 7.8 K/min. Rapid heating as well as rapid cooling of FePt nanoparticles can provide a facile route for the high-throughput production of L10-FePt-based high-density magnetic recording media.

Tailoring the shape and size of wet-chemical synthesized FePt nanoparticles by controlling nucleation and growth with a high magnetic field

A 6 Tesla high magnetic field (HMF) was separately introduced into the nucleation stage and growth stage and into both stages during the wet-chemical synthesis of FePt nanoparticles. The HMF refined particle sizes and increased the nucleation rate in the nucleation stage and tailored shapes and refined sizes in the growth stage. Extension of nucleation time increased the nucleation rate more than that of the HMF, which increasing was higher enough to tailor the shapes of FePt nanoparticles. Controlling nucleation is a feasible strategy to tailor the shapes and sizes of wet-chemical synthesized nanoparticles.

Phase transition of chemically synthesized FePt nanoparticles under high pressure

We present the results of a study related to phase transformation of chemically synthesized FePt nanoparticles under high pressure from face-centered cubic into face-centered tetragonal structure. As-synthesized nanoparticles are around 4.5 nm and show superparamagnetic behavior at 300 K. After annealing under 60 bar pressure of hydrogen at 400 ∘ role=presentation> ∘ ∘ ^{\circ} C for 2 h, nanoparticles exhibit strong ferromagnetic behavior with 5391 Oe coercivity. Results show that high-pressure annealing lowers the decomposition temperature of the surfactants surrounding nanoparticles and partially hinders agglomeration arising from heat treatment. The promising ferromagnetic properties of the FePt nanoparticles after annealing under high pressure make them suitable for ultrahigh-density memory devices.

Dense-plasma-driven ultrafast formation of FePt organization on silicon substrate

This article demonstrates the removal of organic capping and promotion of long-range 2D organization of chemically synthesized FePt nanoparticles dispersed on Si 〈100 〉 substrate by means of pulsed H+ energetic ion irradiation using a dense plasma focus (DPF) device. The irradiation of energetic H+ ions on FePt nanoparticles clearly resulted in enhanced structural and magnetic behaviour of the FePt nanoparticles as a function of plasma focused irradiation shots. Transmission electron microscopy (TEM)/scanning electron microscopy (SEM) images of the FePt nanoparticles clearly show a marked enhancement in average particle size from 2.5 nm for non-irradiated sample to about 28 nm for four plasma focus shots irradiation. The gradual removal of organic capping over chemically synthesized FePt nanoparticles with increasing plasma focus shots exposure is confirmed using Raman spectroscopy. A uniform 2D organization of bimetallic FePt nanoparticles over 1 cm × 1 cm silicon substrate is obtained with three plasma focus shots with better magnetic properties as compared with plasma-untreated FePt nanoparticles. Plasma focused irradiation shots

Fe-Ptナノ粒子とヒドロキシプロピルセルロースからなる熱応答性磁気キャリアの作製

The present paper describes a fabrication of magnetic composite of Fe-Pt nanoparticles and hydroxylpropyl cellulose (HPC) for magnetically guided drug delivery system with a capability of thermo-responsive controlled release. The composites are fabricated by a synthesis of Fe-Pt nanoparticles in a reaction solution containing HPC coated silica particles; Fe-Pt nanoparticles are grown on HPC deposited on the silica particles. The island-like composites of HPC and Fe-Pt NPs are observed to be densely deposited on the silica particles by transmission electron microscopy. Thermal responsiveness is evaluated by temperature-dependence of particle size distribution using dynamic light scattering; the thermal responsiveness is successfully confirmed even after the thermal history up to 533 K during synthesis.

Colloidal Nanoparticle Clusters to produce large FePt nanocrystals

The present work seeks to enlarge the FePt nanocrystal size by submitting Colloidal Nanoparticle Clusters (CNCs) coated by a FeOx shell (FePt@FeOx) to a thermal treatment. The nanostructures were prepared by thermal decomposition in organic media under limited surfactant protection. By adjusting the molar ratio of surfactants it is possible to control the degree of oxidation and aggregation of the CNCs. The FeOx coating of the FePt CNCs resulted to be crucial during the thermal treatment to achieve a controlled crystal growth and induce a structural transition to tetragonal L10 FePt phase producing 31nm nanocrystals with high magnetization and coercivity. Clustering and controlled oxidation is proposed here as a new method to overcome size limitation in the synthesis of FePt nanoparticles.

Effect of Cu doping on the structure and phase transition of directly synthesized FePt nanoparticles

In this work, ternary Cu doped FePt nanoparticles were prepared in hexadecylamine at 320°C by choosing FeCl2 as the Fe source. The experimental results showed that without Cu doping the as-prepared FePt nanoparticles possessed fcc structure and gradually exhibited typical fct diffraction peaks after increasing the Cu doping concentration. TEM images showed that the FePt nanoparticles had larger size and wider size distribution after introducing Cu additive. Magnetic property measurement showed that a coercivity of 4800Oe was obtained when the composition of the ternary nanoparticles reached Fe35Pt45Cu20, in which the content of Fe+Cu was higher than Pt. The research indicates that Cu doping promotes the phase transition of FePt nanoparticles at temperature as low as 320°C.

Synthesis and Characteristics of FePt Nanoparticle Films Under In Situ-Applied Magnetic Field

In situ external magnetic field was applied during the synthesis of FePt nanoparticles via a chemical solution method. FePt nanoparticle films were prepared on Si by a drop-coating method with and without a magnetic field. Annealing at 700 °C in reductive atmosphere was explored to obtain ferromagnetic FePt L10 phase. The effect of in situ-applied magnetic field on the structure, morphology, and magnetic properties of FePt nanoparticle films was characterized. It is found that the applied magnetic field during the chemical synthesis of FePt nanoparticles plays a key role in the crystallinity and magnetic property of FePt nanoparticle films. As-synthesized FePt nanoparticles under the magnetic field are monodispersed and can be self-assembled over a larger area by a dropping method. The applied magnetic field during the synthesis of FePt nanoparticles not only significantly improves the nanoparticles’ c-axis preferred orientation but also benefits the phase transition of FePt nanoparticles from face-centered cubic to face-centered tetragonal structure during the annealing process. The FePt nanoparticle films derived under magnetic field also show some magnetic anisotropy.

Preparation of ICG-FePt nanoparticles promising for magnetic resonance imaging contrast agent and hyperthermia applications

The use of superparamagnetic FePt nanoparticle for biomedical applications has been investigated. Indocyanine green (ICG) is a tricarbocyanine approved by the U.S. FDA for use in humans for fluorescence imaging and diagnosis in clinical applications. Using a simplified method, we successfully synthesized FePt nanoparticles and modified the surfaces of the nanoparticles with various functional agents. By heating the FePt nanoparticles, 2-aminoethanethiol and indocyanine green were transferred onto the FePt nanoparticles without the use of toxic chemicals, and multiple functional nanomaterials were produced.The promising nanotheranostic materials were constructed for fluorescence and magnetic guidance dual-modals by the introduction of chemical bonds between ICG and 2-aminoethanethiol, which was transferred onto magnetic FePt nanoparticles. It was proven that the resulting composites with an average diameter of 1.85nm could be stimulated to high temperature elevation rates with high-frequency induction heating. Different concentrations of FePt nanoparticles had excellent heating rates that were at least 0.016cal/s, which demonstrated that the materials could serve as an outstanding agent for hyperthermia therapy in cancer. 3T Magnetic Resonance (3T-MR) imaging showed that the nanoparticles had excellent concentration-dependent contrasting effects, demonstrating promise for use as a contrast agent with good biocompatibility.

Size control synthesis and high coercivity L10-FePt nanoparticles produced by iron (III) acetylacetonate salt

Monodisperse 4.11nm FePt nanoparticles were synthesized via chemical co-reduction of iron (III) acetylacetonate and platinum (II) acetylacetonate by 1,2-hexadecanediol as a reducing agent. Then through the seed mediated growth process smaller sized FePt nanoparticles are used as seeds for the growth of larger sized particles. There is no specific limitation to achieve upper size range by this method. In this work, we have successfully synthesized FePt nanoparticles up to 8.32nm. After annealing these particles become ferromagnetic and their coercivirty increases with increasing particle sizes and reaches a maximum value of 17760Oe for size of 8.32nm.

A New Strategy for the Synthesis of Size-controlled L1&lt;sub&gt;0&lt;/sub&gt; FePt Nanoparticles on Nanotube Substrate

In this paper, a CVD method is used for the synthesis of multi-wall carbon nanotubes (MWCNT) which have been purified and functionalized. The approach consists of thermal oxidation and subsequent chemical oxidation. According to TEM images, the CNTs have a diameter about 20-30 nm. We synthesized the FePt nanoparticles on the surface of the functionalized carbon nanotubes through a polyol process. The synthesized FePt nanoparticles have the chemicallydisordered face-centered cubic (fcc) structure with superparamagnetic behavior and with a size of about 2.5 nm. To achieve phase transition from fcc to ordered structure (fct-L10 phase), high-temperature annealing under a reducing atmosphere (90% Ar + 10% H2) is required. The CNTs as a substrate prevent the aggregation of particles during thermal treatment. The FePt nanoparticles after phase transition have ferromagnetic behavior. Furthermore, they have finite size with an average about 5.6 nm and their coercivity reaches to 5.1 KOe at 700°C. We characterized the structure, composition and magnetic properties of FePt/CNT by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). Keywords: Carbon nanotubes, chemically-disordered structure, fcc and fct- L10 structure, FePt nanoparticles, ferromagnetic, superparamagnetic.

Substituent effect of Fe(β-diketonate)3 on the control of self-assembly FePt-based nanoparticles

Three Fe(β-diketonate)3 compounds namely Fe(tmhd)3 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato), Fe(hfac)3 (hfac = hexafluoroacetylaceto), and Fe(dbm)3 (dbm = dibenzoylmethane) were used as substitutes to Fe(acac)3 (acac = acetyleacetonate) in the synthesis of FePt nanoparticles. The obtained superparamagnetic nanoparticles are 4–5 nm in diameter without showing a large size variation with substituent Fe(β-diketonate)3. The synchrotron X-ray absorption spectroscopy confirmed the energy dispersive spectroscopy that as-synthesized nanoparticles were composed of iron oxides and metallic FePt3 alloys. By employing Fe(hfac)3, the Fe fraction was reduced and the magnetization was modest. The use of Fe(dbm)3 as starting materials gave rise to densely packed FePt3/Fe2O3 heterodimers. The replacements of Fe(acac)3 by Fe(tmhd)3 led to the long-range order of nanoparticle assembly with the narrowest size distribution.

High pressure synthesis of FePt nanoparticles with controlled morphology and Fe content

Magnetic nanoparticles (MNPs) are intensively researched due to their high potential in biomedicine, catalysis, and high density information storage. FePt NPs could be an alternative for commonly used magnetite NPs and the synthesis of FePt NPs is an active area of research. The challenge is to increase the Fe content and saturation magnetisation of FePt NPs so that they can be used in many practical applications. Fine tuning of synthetic methods is required in order to achieve the enhanced magnetic properties of FePt nanoparticles and novel methods are being sought. Herein, use of an autoclave is shown to increase the Fe content, crystallinity and the subsequent magnetic properties of FePt pseudo cube nanoparticles compared to those synthesised under atmospheric pressure. Decreasing the amount of oleic acid is also shown to increase the iron content and can lead to elongated FePt nanoparticles under normal pressure. Further application of nanoparticles synthesised in organic media often requires functionalisation or exchange of stabiliser chemicals. Greater demand for control over such functionalisation requires more information about nanoparticle–stabiliser chemical interactions. Infra-red studies indicate mono and bidentate coordination with oleic acid, however shifts of spectra show that the strength of the bidentate interactions weaken with increasing oleic acid amount.

Decoration of carbon nanotube with size-controlled L10-FePt nanoparticles for storage media

In this work, first multi-wall carbon nanotubes (MWCNTs) with outer diameter about 20–30 nm are synthesized by a CVD method; they have been purified and functionalized with a two-step process. The approach consists of thermal oxidation and subsequent chemical oxidation. Then, monosize FePt nanoparticles along carbon nanotubes surface are synthesized by a Polyol process. The synthesized FePt nanoparticles are about 2.5 nm in size and they have superparamagnetic behavior with fcc structure. The CNTs surfaces as a substrate prevent the coalescence of particles during thermal annealing. Annealing at the temperature higher than 600 ∘C for 2 h under a reducing atmosphere (90 % Ar + 10 % H2) leads to phase transition from fcc to fct-L10 structure. So, the magnetic behavior changes from the superparamagnetic to the ferromagnetic. Furthermore, after the phase transition, the FePt nanoparticles have finite size with an average of about 3.5 nm and the coercivity of particles reaches 5.1 kOe.

BIOMIMETIC SYNTHESIS OF FePt NANOPARTICLES ON MULTI-WALLED CARBON NANOTUBES FOR FUNCTIONAL NANOMATERIALS

We present a facile green biomimetic synthesis of FePt nanoparticles (NPs) on the sidewalls of multi-walled carbon nanotubes (CNTs). A core-shell globular protein, ferritin (Fr), was bound onto Z-glycine N-succinimidyl ester (Z-Gly-OSu) modified CNTs and served as precursor to create FePt NPs at the core part of Fr. Biomimetic synthesis of FePt NPs was carried out by chemical reducing of Fe2+ and [Formula: see text] ions that transferred into the core part of Fr molecules. The created one-dimensional CNT- FePt nanohybrids were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized CNT- FePt nanohybrids show multi-properties of high water-solubility, ferromagnetism, and electrocatalytic activity.

PREVENTION OF SINTERING DURING ANNEALING PROCESS OF FePt NANOPARTICLES COATED WITH ZnO SHELL

Monodispersed 4.1 nm FePt nanoparticles with narrow size distribution were successfully synthesized by the chemical polyol process with co-reduction of Fe (acac)3 and Pt (acac)2 in the presence of 1,2-hexadecanediol as a reducing agent. To achieve hard ferromagnetic behavior with L10 phase and face center tetragonal (fct) structure, high temperature annealing is performed. Annealing causes the surfactant surrounding particles to decompose and agglomeration of particles occurs. In the present work, chemically synthesized FePt nanoparticles were coated with nonmagnetic ZnO oxide shell to prevent them from sintering. Coercivity of FePt and FePt/ZnO nanoparticles increases from 5 kOe to 10 kOe and 1.8 kOe to 6 kOe respectively, with the increasing annealing temperatures from 650 to 750°C.