Low-Temperature Co-Precipitation Synthesis of HoFeO3 Nanoparticles

In this research, we investigate and discuss the characteristics of HoFeO3 nanoparticles synthesized by the co-precipitation method at low temperature (t° ≤ 4 °C). The single-phase HoFeO3 samples with the orthorhombic structure formed after annealing of the precipitates at different temperatures up to 950 °C. The annealed HoFeO3 nanoparticles have an average crystal size of 10–20 nm (SEM, TEM). UV-Vis spectrum of HoFeO3 sample annealed at 750 °C showed strong UV and Vis absorption with small optical energy gap (Eg = 1.56 eV). In the range temperature of 100–300 K, the HoFeO3 samples showed superparamagnetic behaviour at 5 kOe with high magnetization (Ms = 1.3–2.4 emu/g) and very low susceptibility (χ << 1).

Atomic layer deposition of superparamagnetic ruthenium-doped iron oxide thin film

In atomic layer deposited Ru-doped α-Fe2O3 thin films superparamagnetic behaviour of nanocrystallites is observed with the magnetic coercive force up to 3 kOe.

Superparamagnetic behaviour of metallic Co nanoparticles according to variable temperature magnetic resonance

Combined power of 59Co Internal Field nuclear magnetic resonance (IF NMR) and ferromagnetic resonance (FMR) allows studying structure and morphology of metallic Co nanoparticles.

Superparamagnetic Behaviour and Surface Analysis of Fe3O4/PPY/CNT Nanocomposites

The superparamagnetic property of nanomaterials such as Fe3O4 has been considered to be promising for various applications. In this paper, Fe3O4/PPY/CNT nanocomposites were synthesized with utilizing natural iron sand by a coprecipitation method. The as-precipitated Fe3O4 NPs were combined with carbon nanotubes (CNTs) using conductive polypyrrole (PPY) as linking agents. The Fe3O4/PPY/CNT nanocomposites were systematically characterized by FE-SEM, EDS, XRD, BET, and FTIR. Furthermore, the effects of CNTs on magnetic and thermal properties of nanocomposites were investigated by VSM and thermal gravimetric analysis (TGA), respectively. The composites exhibited significant decrease of coercivity value with the content of CNTs increasing. The VSM result confirmed that Fe3O4/PPY/CNT nanocomposites were superparamagnetic. It was found that by increasing the amounts of CNTs, the magnetization of Fe3O4/PPY/CNT nanocomposites gradually decreased. The addition of CNTs is intended to improve the mesoporous property as proved by BET analysis which has the potential application as a nanocatalyst.

Thermoanalytical, optical, and magnetic investigations on nanocrystalline Li0.5Fe2.5O4 and resulting ceramics prepared by a starch-based softchemistry synthesis

Nanocrystalline Li0.5Fe2.5O4 was prepared by a starch-based soft-chemistry synthesis. Calcining of the (LiFe)-gel between 350 and 1000 °C results in Li0.5Fe2.5O4powders with crystallite sizes from 13 to 141 nm and specific surface areas between 35 and 7.1 m2 g−1. XRD investigations reveal the formation of ordered Li0.5Fe2.5O4. Sintering between 1050 and 1250 °C leads to ceramics with relative densities of 67−95 % consisting ofgrains between 0.3 and 54 μm. As the sintering temperature increases a rising weight loss ofthe ceramic samples was observed due to the loss of Li2O. Temperature-dependent magnetic measurements indicate a superparamagnetic behaviour for the nano-sized samples. Field-dependent measurements at 3 K of ceramics sintered between 1050 and 1200 °C showincreasing saturation magnetization values (Ms) of 70.0 to 73.0 emu g−1 most likely due to the formation of lithium vacancies and a decrease of the inversion parameter. The magnetization drops down to 67.7 emu g−1 after sintering at 1250 °C caused by the formation of hematite.Diffuse reflectance spectra reveal an indirect allowed band gap decreasing from 1.93 to 1.60 eV depending on thermal treatment. DSC measurements of the order - disorder phase transition on nano-sized powders and bulk ceramics exhibit transition temperatures between 734 and 755 °C and enthalpy changes (ΔtrsH) ranging from 5.0 to 13.5 J g−1. The linear starch was found to be 11.4⋅10−6 K−1.

Pseudo-superparamagnetic behaviour of barium hexaferrite particles

Observed morphology evolution of BaFe12O19 ferrite particles, obtained with different relative amounts of surfactant used.

Functionalizing Multifunctional Fe3O4 Nanoparticle-Based Biocompatible, Magnetic and Photoluminescent Nanohybrids: Preparation and Characterization

A combination of ring-opening polymerization (ROP) and coordination chemistry methodology has been expanded for the synthesis of a multifunctional, biocompatible, magnetic, luminescent nanohybrid complex comprising magnetite (Fe3O4) nanoparticles (MNPs), poly(ε-caprolactone) (PCL) and europium ions (Eu3+). The structural and morphological characteristic of the nanohybrid intricate were studied by appropriate spectrum and physical researches. The superparamagnetic behaviour and unique Eu3+ fluorescence properties with a high emission intensity of MNP-PCL-Eu3+ were investigated via measurements with a superconducting quantum interference equipment magnetism and fluorescence spectroscopy.

Preparation and characterization of nano-sized magnesium ferrite powders by a starch-gel process and corresponding ceramics

The synthesis and characterization of nano-sized MgFe2O4 by a starch-gel methodis described herein. A phase-pure nano-sized MgFe2O4 powder (1a) was obtained aftercalcining a (MgFe)-starch gel at 550 °C. The powder has a specific surface area of 60.6 m2/gand a crystallite size of 9 nm. TEM investigations reveal particles in the range of 7 to 15 nm.The activation energy of the crystallite growth process was calculated as 89 ± 14 kJ/mol. Theshrinkage and sintering behaviour of resulting compacts were studied. UV−VIS investigationsof the nano-sized powder 1a reveal an optical band gap of 2.38 eV, whereas calcination at1100 °C (powder 1g) leads to a crystallite size of 129 nm and a band gap of 2.16 eV.Magnetization loops at 300 K and the temperature dependence of both the field-cooled (FC) and the zero-field-cooled (ZFC) magnetization indicate a superparamagnetic behaviour. The blocking temperature for powder 1a was determined as 140 K at a field of H = 500 Oe. Wefound different saturation magnetizations (Ms) depending on the calcination temperature. Calcination at 550 °C (1a) results in Ms = 20.0 emu/g which increases with calcinationtemperature to a maximum of 37.7 emu/g for powder 1e calcined at 900 °C. Ceramic bodiessintered between 1450 and 1600 °C exhibit Ms values of 25−28 emu/g. Magnetic investigations at 10 K on powders 1a−1g show hysteresis loops with coercivities up to 950Oe, remanences to 10 emu/g and Ms values to 50.4 emu/g. Additionally, the nano-scaled powders show a shift of the hysteresis loops.

A Tailor-Made Protocol to Synthesize Yolk-Shell Graphene-Based Magnetic Nanoparticles for Nanomedicine

A simple tailor-made protocol to synthesize graphene-based magnetic nanoparticles (GbMNPs) for nanomedicine is herein reported. Different GbMNPs with very distinctive physicochemical and toxicological properties were synthesized by adjusting the number of carbon precursors in the coating of superparamagnetic iron oxide nanoparticles. In vitro tests show the ability to use these GbMNPs as intelligent and on-demand drug nanocarrier systems for drug delivery, exhibiting the following features: good colloidal stability, good loading capacity of the chemotherapeutic drug doxorubicin, high pH-controlled release of the encapsulated drug (targeting tumour acidic pH conditions), superparamagnetic behaviour and biocompatibility. Due to their combined properties (i.e., physicochemical, magnetic, and biocompatibility), GbMNPs show high potentiality to be combined with other biomedical techniques, such as magnetic hyperthermia, which can represent an enhancement in the treatment of cancer.