Synthesis of carboxyl superparamagnetic ultrasmall iron oxide (USPIO) nanoparticles by a novel flocculation-redispersion process

We report a novel flocculation-redispersion method to synthesize and purify the biocompatible superparamagnetic ultrasmall iron oxide (USPIO) nanoparticles coated with carboxyl dextran derivative. First, USPIO nanoparticles were synthesized and flocculated to form the large clusters through bridging effect of polyvinyl alcohol (PVA) during coprecipitation process. Then the flocculated USPIO was separated and purified from the solution conveniently through magnetic sedimentation. Finally, USPIO in the clusters were released again and well dispersed through electrostatic repelling effect of citric acid with the aid of ultrasonic. The dispersed carboxyl-functionalized USPIO was conjugated with the monoclonal antibodies. And it has been proved that the antibodies anchored on USPIO still retained their bioactivity after the conjugation. These results implied that the USPIO synthesized have good potential as active targeting molecular probe in biomedical application.     

Magnesium oxide nanocrystals via thermal decomposition of magnesium oxalate

The present work reports the synthesis of magnesium oxide (MgO) nanocrystals via a thermal decomposition route and the study of physicochemical properties of products. The MgO nanocrystals were prepared from magnesium oxalate powders as precursor. Transmission electron microscopy (TEM) analysis demonstrated MgO nanocrystals with an average diameter of about 20−25 nm. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electronic diffraction (SAED), and Fourier transform infrared (FT-IR) spectroscopy. Optical absorption and photoluminescence emission properties of MgO nanocrystals were investigated.     

Sonochemical synthesis of amorphous nanoscopic iron(III) oxide from Fe(acac)3

Amorphous nanoscopic iron(III) oxide with interesting magnetic properties was prepared by sonolysis of Fe(acac)(3) under Ar in tetraglyme with a small amount of added water. The organics content and the surface area of the Fe(2)O(3) nanoparticles can be controlled with an amount of water in the reaction mixture and it increases from 48 m(2)g(-1) for dry solvent up to 260 m(2)g(-1) when wet Ar is employed. For further monitoring of the particle size and morphology and for the study of the surface, magnetic and thermal properties, the sample with 2 vol.% of H(2)O was chosen. SEM showed nanoscopic composite particles of a uniform size distribution and nearly spherical shapes with an estimated diameter of 20 nm. Such composites are built from amorphous iron(III) oxide nanoparticles (3 nm) embedded in an acetate matrix as proved by TEM and IR spectroscopy. Temperature-dependent M?ssbauer spectra demonstrate a very narrow magnetic transition with an unusually low transition temperature around 25K reflecting the system of magnetically non-interacting ultrasmall particles with a narrow size distribution. The in-field (5T) M?ssbauer spectrum recorded at 5K shows a minimum change compared to the zero-field spectrum indicating an absence of the long-range magnetic ordering. The composite particles are thermally stable up to 150 degrees C, which is confirmed by DSC, TG, and by the constant surface area. At higher temperatures, acetate groups are removed from the particle surface, which is documented by the increased surface area and disappearance of their IR bands.     

Studies of magnetite nanoparticles synthesized by thermal decomposition of iron (III) acetylacetonate in tri(ethylene glycol)

In this paper, water-soluble magnetite nanoparticles have been directly synthesized by thermal decomposition of iron (III) acetylacetonate, Fe(acac)₃ in tri(ethyleneglycol). Size and morphology of the nanoparticles are determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements while the crystal structure is identified using X-ray diffraction (XRD). Surface charge and surface coating of the nanoparticles are recognized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectra (XPS) and zeta potential measurements. Magnetic properties are determined using vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The results show that as-prepared magnetite nanoparticles are relatively monodisperse, single crystalline and superparamagnetic in nature with the blocking temperature at around 100 K. The magnetite nanoparticles are found to be highly soluble in water due to steric and electrostatic interactions between the particles arising by the surface adsorbed tri(ethyleneglycol) molecules and associated positive charges, respectively. Cytotoxicity studies on human cervical (SiHa), mouse melanoma (B16F10) and mouse primary fibroblast cells demonstrate that up to a dose of 80 μg/ml, the magnetic nanoparticles are nontoxic to the cells. Specific absorption rate (SAR) value has been calculated to be 885 and 539 W/gm for samples with the iron concentration of 1 and 0.5 mg/ml, respectively. The high SAR value upon exposure to 20 MHz radiofrequency signifies the applicability of as-prepared magnetite nanoparticles for a feasible magnetic hyperthermia treatment.     

Synthesis of magnetite nanoparticles via a solvent-free thermal decomposition route

Superparamagnetic nanoparticles have been widely applied in various bio-medical applications. To date, it is still a challenge to synthesize nanosized Fe₃O₄ particles with controlled size and distribution. In this paper, a novel solvent-free thermal decomposition method is reported for synthesizing Fe₃O₄ nanoparticles. Size and morphology of the nanoparticles are determined by TEM while the structure of the nanoparticles is identified by FTIR, XPS and TGA measurements. Magnetic properties of the obtained particles are determined using VSM and SQUID measurement. The particle size of the Fe₃O₄ can be tailored by adjusting either reaction temperature or time. When the reaction temperature is increased to 330 °C and the reaction time is extended to 4 h, the average particle size of the obtained nanoparticles is ∼9 nm, while Ms value reaches ∼76 emu/g. The as synthesized Fe₃O₄ nanoparticles show well-established superparamagnetic properties with the blocking temperature at around 100 K.     

A study of the thermal decomposition of iron(II) and iron(III) rubidium oxalates using the Mössbauer effect

The thermal decompositions of Rb₃Fe(ox)₃ 4 H₂O and Rb₂Fe(ox)₂ 6 H₂O have been studied using Mössbauer spectroscopy and thermal analysis methods (TGA, DSC). It is shown that after dehydration, the ferric complex is reduced into a ferrous compound, with a large quadrupole splitting (3.84 mm/s), which corresponds to the anhydrous form of Rb₂Fe(ox)₂ 6 H₂O.     

Optical properties of core/multishell CdSe/Zn(S,Se) nanocrystals

CdSe nanocrystals are now known as highly efficient fluorescent light sources. Their efficiency is however strongly dependent on the quality of the passivation layers. We show here that using a ZnSe/ZnS bi-layer shell leads to a larger photoluminescence yield than both ZnSe and ZnS simple shells. The intermediate ZnSe layer acts as a lattice parameter adaptation layer to improve on the core/shell interface quality, while the ZnS outer shell maximizes the exciton confinement.     

Preparation of Fe3O4/polystyrene composite particles from monolayer oleic acid modified Fe3O4 nanoparticles via miniemulsion polymerization

Fe₃O₄/polystyrene composite particles were prepared from oleic acid (OA) modified Fe₃O₄ nanoparticles via miniemulsion polymerization. It was concluded that the surface properties of OA modified magnetite nanoparticles have a great effect on preparation of the composite particles. When Fe₃O₄ nanoparticles coated by multilayer of OA was employed, there were large amounts of free polystyrene particles in the product. Fe₃O₄/polystyrene composite particles with defined structure and different magnetite content can be readily prepared from monolayer OA modified Fe₃O₄ nanoparticles. It was concluded that surface of the monolayer OA modified Fe₃O₄ nanoparticles is more hydrophobic than that of the multilayer coated ones, thus improving the dispersibility of the Fe₃O₄ nanoparticles in styrene monomer and allowing preparation of the Fe₃O₄/polystyrene composite particles with defined structure and controllable magnetite content.     

Characterization of iron(III) oxide films used for photoelectrode by means of cems

Thin iron oxides deposited on semi-conductive glass by a spray pyrolysis technique were analysed by Conversion Electron Mössbauer Spectrometry (CEMS). Iron oxide deposited on SnO₂ coated glass was composed of a large grained particles of crystalline α?Fe₂O₃, which showed sextet. The doublet and sextet appeared in CEM spectra of iron oxides deposited on In₂O₃ and WO₃ coated glasses. The sextet was due to α?Fe₂O₃ and the doublet was attributted to the superparamagnetic microcrystalline α?Fe₂O₃ (≈15nm) rather than to spinel compounds of iron. The iron oxide deposited on ZnO coated glass gave a doublet in CEM spectra. It was supporsed to be due to very fine particle of α?Fe₂O₃ (<100nm). It was found that iron oxide films obtained by spray pyrolysis were dependent on the kinds and the temperature of the semi-conductive materials coated on glass.     

A novel precursor for synthesis of metallic copper nanocrystals by thermal decomposition approach

[Bis(2-hydroxy-1-naphthaldehydato)copper(II)] complex, as a novel precursor, was employed in thermal decomposition process to synthesize metallic copper nanoparticles using oleylamine (C₁₈H₃₇N) as capping agent. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-vis) spectroscopy. The synthesized copper nanoparticles have a fcc structure with average size 20-35 nm.     

Superparamagnetic iron oxide nanoparticles as a liver MRI contrast agent: Contribution of microencapsulation to improved biodistribution

We have developed a new method of synthetizing superparamagnetic iron oxide nanoparticles, consisting in the modifications of Molday's method, which ensures high relaxivity (2.4 10⁵ s⁻¹·M⁻¹·L), good chemical stability, singular biodistribution and a considerable safety margin. The ED (Efficace Dose) to LD50 ratio is instead of for Gd-DTPA. In order to develop a magnetite-delivery system to the liver we have incorporated the nanoparticles into biodegradable synthetic microcapsules. Encapsulated ⁵⁹Fe oxide nanoparticles are injected into rats; in these conditions the sequestration is 9-fold greater in liver and 6 and 5 times lower in blood and carcase, respectively. This modification of the biodistribution enables the use of magnetite containing microcapsules at only 0.3 mg/kg iron to obtain an improved contrast in liver.     

Mössbauer study of the thermal decomposition of cesium tris(oxalato) ferrate(III)dihydrate

The thermal decomposition of cesium tris(oxalato)ferrate(III) dihydrate in nitrogen has been studied using Mössbauer spectroscopy, thermogravimetric and differential thermal analyses. The mechanisms of the various stages in the decomposition are discussed and correlated to the results of the Mössbauer measurements.     

Simultaneous determination of aluminum (III) and iron (III) by first-derivative spectrophotometry in alloys

A highly sensitive and selective first-derivative spectrophotometric method has been developed for the determination of aluminum and iron in mixtures. The method is based on the formation of the binary complexes of aluminum and iron with Alizarin yellow R (AYR) 5-[4-nitrophenylazo]salicylic acid at pH 2.0 with molar absorptivity of 1.1∙10⁴ l⋅mol^–1⋅cm^–1. A zero-crossing technique is found suitable for the direct measurement of the first derivative value at the specified wavelength, so aluminum and iron were thus determined in the ranges 1.3–5.4 μg/ml and 1.1–8.3 μg/ml, respectively, in the presence of both components. The detection limits were found to be 1.4 ng/ml for aluminum and 2.8 ng/ml for iron. The relative standard deviations were in all cases less than 1.5%. The proposed method was successfully applied for the simultaneous determination of aluminum and iron in certified reference aluminum samples.     

Analysis of thermal expansivity of iron (Fe) metal at ultra high temperature and pressure

In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state is modified by incorporating the effect of thermal pressure. The calculated values of pressure for different isotherms and isochors and thermal expansivity (α) as a function of both temperature and pressure have been compared with those values obtained by Isaak et al and Wasserman et al.      

Preparation and application of magnetic poly(styrene-glycidyl methacrylate) microspheres

A novel method for the preparation of polymer-based, magnetic microspheres is proposed. Pre-made, poly(styrene-glycidyl methacrylate) (PS-GMA) particles of micron size were swollen by a mixture of N-methyl-2-pyrrolidone and water, and then incubated with superparamagnetic nanoparticles. The nanoparticles were allowed to diffuse into polymer microspheres during the incubation, became entrapped and made the polymer microspheres superparamagnetic. These magnetic PS-GMA microspheres were chemically modified and then coupled with single-stranded oligonucleotides as probes for DNA hybridization. The immobilized probes showed repeatable capture of target oligonucleotides.     

Preparation and characterization of neodymium tin oxide pyrochlore nanocrystals by the hydrothermal method

Fine powder of Nd₂Sn₂O₇ nanocrystals with a phase-pure pyrochlore structure were synthesized at low temperatures (200 °C) for 12 h through the hydrothermal method in alkaline medium. The pH value of the solution was adjusted by addition of 1.0 M NaOH solution to reach 11, and basically above 11 was shown to accelerate the crystallization process. The samples were characterized by X-ray diffraction and Fourier Transformed InfraRed spectra. Scanning electron microscopy was used for morphologic evolution. Furthermore, photoluminescence characterization and UV–VIS spectra of the Nd₂Sn₂O₇ pyrochlore nanocrystals showed clear luminescence and absorption peaks, and band gap energy were calculated using emission and absorption data.     

A general method for preparing lanthanide oxide nanoparticles via thermal decomposition of lanthanide(III) complexes with 1-hydroxy-2-naphthoic acid and hydrazine ligands

Six new lanthanide(III) complexes (i.e., [Ln(L)₂(NA)_1.5]·3H₂O, where Ln=La(III), Pr(III), Nd(III), Sm(III), Gd(III), and Ce(III) and L and NA indicate N₂H₄ and C₁₀H₆(1-O)(2-COO), respectively) with 1-hydroxy-2-naphthoic acid [C₁₀H₆(1-O)(2-COOH)] and hydrazine (N₂H₄) as co-ligands were characterized by elemental, FTIR, UV-visible, and XRD techniques. In the FT-IR spectra, the N-N stretching frequency in the range of 981–949 cm⁻¹ demonstrates evidence of the presence of coordinated N₂H₄, indicating the bidentate bridging nature of hydrazine in the complexes. These complexes show symmetric and asymmetric COO⁻ stretching from 1444 to 1441 cm⁻¹ and 1582 to 1557 cm⁻¹, respectively, indicating bidentate coordination. TG-DTA studies revealed that the compounds underwent endothermic dehydration from 98 to 110 °C. This was followed by the exothermic decomposition of oxalate intermediates to yield the respective metal oxides as the end products. From SEM images, the average size of the metal oxide particles prepared by thermal decomposition of the complexes was determined to be 39–42 nm. The powder X-ray and SEM coupled with energy dispersive X-ray (EDX) studies revealed the presence of the respective nano-sized metal oxides. The kinetic parameters of the decomposition of the complexes were calculated using the Coats-Redfern equation.     

Heat capacity of a five-coordinated iron(III) complex,iodobis (N,N-Dimethyldithiocarbamato) iron(III), between 0.4 and 300 K

The heat capacity of iodobis (N, N-dimethyldithiocarbamato)iron(III) has been measured between 0.4 and 300 K. Based on the heat capacity and entropy at low temperatures it was found that the present sample consists of a mixture of monomer (ca. 40%) and dinier (ca. 60%); the former brings about a λ-type phase transition from an antiferromagnetic to a paramagnetic state at T_N = (1.65 ±0.04) K while the latter exhibits a Schottky-ype anomaly due to antiferromagnetic dimeric coupling, the effect of which becomes dominant below ca. 0.7 K. The zero-field splitting parameter of a single ferric ion was estimated to be $\text{D}\text{k}\text{=}\text{D}{}_{\mathrm{D}}\text{k}\text{= 14 K}$ for the monometer and the dimer, while the dimeric coupling constant was $\text{J}{}_{\mathrm{D}}\text{k}\text{= ?0.15 K}$. The entropy at low temperatures cannot be accounted for solely by the spin manifold. Additional contribution from a tunnel-splitting of the rotational levels of four constituent methyl-groups has been discussed. In this case, the level splitting of the ground state is 2.5 J mol^?1 and the barrier height of hindering potential is 2.3 kJ mol^?1.