Formation Of Iron Oxide Nanoparticles Research Articles

Formation Mechanisms of Iron Oxide Nanoparticles in Different Nonaqueous Media

The formation of iron oxide nanoparticles in a solvothermal synthesis with two different nonaqueous solvents, benzyl alcohol (BA) and triethylene glycol (TEG), was studied. Additionally, a scale-up of the synthesis from lab scale autoclaves (45 mL volume) to a 1.5 L reactor was performed. The differences in both reaction vessels as well as for both solvents were investigated regarding the particle size and crystallinity, the magnetic properties, and the stability of the produced particles. A two-step mechanism was identified, with a fast particle formation step and a distinct, slower crystallization step resulting in a strong increase in magnetization. Strong differences in the particle formation between the two reaction media were identified. The stability of the produced particles against agglomeration was screened by a qualitative comparison of sedimentation time in different polar and nonpolar solvents.

Sonochemical formation of iron oxide nanoparticles in ionic liquids for magnetic liquid marble

Ionic liquids (ILs)-stabilized iron oxide (Fe(2)O(3)) nanoparticles were synthesized by the ultrasonic decomposition of iron carbonyl precursors in [EMIm][BF(4)] without any stabilizing or capping agents. The Fe(2)O(3) nanoparticles were isolated and characterized by X-ray powder diffraction, transmission electron microscopy and susceptibility measurements. The physicochemical properties of ILs containing magnetic Fe(2)O(3) nanoparticles (denoted as Fe(2)O(3)@[EMIm][BF(4)]), including surface properties, density, viscosity and stability, were investigated in detail and compared with that of [EMIm][BF(4)]. The Fe(2)O(3)@[EMIm][BF(4)] can be directly used as magnetic ionic liquid marble by coating with hydrophobic and unreactive polytetrafluoroethylene (PTFE), for which the effective surface tension was determined by the puddle height method. The resulting magnetic ionic liquid marble can be transported under external magnetic actuation, without detachment of magnetic particles from the marble surface that is usually observed in water marble.

Ultrasonic-assisted synthesis and magnetic studies of iron oxide/MCM-41 nanocomposite

Iron oxide nanoparticles were stabilized within the pores of mesoporous silica MCM-41 amino-functionalized by a sonochemical method. Formation of iron oxide nanoparticles inside the mesoporous channels of amino-functionalized MCM-41 was realized by wet impregnation using iron nitrate, followed by calcinations at 550 °C in air. The effect of functionalization level on structural and magnetic properties of obtained nanocomposites was studied. The resulting materials were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy and selected area electron diffraction (HRTEM and SAED), vibrating sample and superconducting quantum interface magnetometers (VSM and SQUID) and nitrogen adsorption–desorption isotherms measurements. The HRTEM images reveal that the most of the iron oxide nanoparticles were dispersed inside the mesopores of silica matrix and the pore diameter of the amino-functionalized MCM-41 matrix dictates the particle size of iron oxide nanoparticles. The obtained material possesses mesoporous structure and interesting magnetic properties. Saturation magnetization value of magnetic iron oxide nanopatricles stabilized in MCM-41 amino-functionalized by in situ sonochemical synthesis was 1.84 emu g −1. An important finding is that obtained magnetic nanocomposite materials exhibit enhanced magnetic properties than those of iron oxide/MCM-41 nanocomposite obtained by conventional method. The described method is providing a rather short preparation time and a narrow size distribution of iron oxide nanoparticles.

Atmospheric‐Pressure, Liquid‐Phase, Selective Aerobic Oxidation of Alkanes Catalysed by Metal–Organic Frameworks

Aerobic oxidation of cyclooctane to its corresponding ol/one mixture at atmospheric pressure and in the liquid phase is efficiently promoted by an Fe(BTC) (BTC=1,3,5-benzenetricarboxylate) metal-organic framework, incorporating N-hydroxyphthalimide and in several cases reaches a selectivity over 90% at 28% conversion. This catalytic system is further extended to other hydrocarbons, such as ethylbenzene and 1,2,3,4-tetrahydronaphthalene (tetralin), with high selectivity (>85%). This high selectivity in the product distribution arises from a radical reaction mechanism that occurs inside a hydrophobic cavity that preferentially adsorbs hydrocarbons over their corresponding alcohols. The system can be reused although there is a gradual decrease in turnover frequency, caused by minor changes in the crystal structure due to the formation of iron oxide nanoparticles. Given the sustainable nature of the oxidant and the mild conditions used, this discovery could serve to develop a new catalyst generation for the oxyfunctionalisation of hydrocarbon feedstocks with the real possibility of finding industrial application.

Understanding the Formation of Iron Oxide Nanoparticles with Acicular Structure from Iron(III) Chloride and Hydrazine Monohydrate

Iron oxide nanoparticles, nanowires, and nanobelts were prepared from a 50 vol % ethanol solution of 28 mM iron(III) chloride and 0.3 mM polyethylene glycol (20 kDa) by hydrothermal treatment at 120 °C, using hydrazine monohydrate (N2H4) as a reducing agent. Factors governing phase and morphology of the iron oxide nanoparticles were studied. The amount of hydrazine added affected the hydrolysis of iron(III); therefore, the type of iron oxyhydroxide formed; this in turn controlled whether akaganeite, goethite, hematite, or magnetite was obtained after the hydrothermal treatment step. For conditions that favored the formation of magnetite, the addition rate of hydrazine was shown to affect the reduction of iron(III) to iron(II) and, hence, the relative amount of magnetite and goethite in the final product. Increasing the pH of the precursor solution to 14 resulted in the formation of magnetite nanobelts. Phase analysis of the intermediate products showed that the magnetite nanobelts were formed from the dis...

Influence of Polyols on the Formation of Iron Oxide Nanoparticles in Solvothermal System

We reported a simple solvothermal route in phase-controllable synthesis of iron oxide nanoparticles by using polyols as solvent. Magnetite and hematite are selectively synthesized while Fe(NO3)3.9H2O is used as single iron source and without any additives. While ethylene glycol, 1,2propanediol, 1,3-butanediol, or glycerol is used as solvents, magnetite nanoparticles are obtained, and the average particle sizes vary from 10 to 40 nm. While 1,4-butanediol or 1,5-pentanediol is used as solvents, hematite nanoparticles are obtained. Our results suggest that the polyols with neighboring hydroxyl groups is favorable for the formation of magnetite nanoparticles.

Synthesis of ordered iron oxide nanoparticle arrays in planar DNA complexes

The formation of iron oxide nanoparticles in planar DNA complexes immobilized on substrates has been studied in reactions involving only biogenic reagents (ferritin and ascorbic acid) in aqueous solutions under normal conditions. Using transmission electron microscopy, we revealed ordered quasi-linear arrays of iron oxide nanoparticles 2–4 nm in diameter, which probably resulted from nanoparticle binding to linear DNA molecules. The electron diffraction patterns of the synthesized nanoparticles are characteristic of polycrystalline magnetic iron oxide (magnetite of maghemite) nanoparticles and point to good crystallinity of the nanoparticles. Our results demonstrate the feasibility of the synthesis of ordered arrays of iron oxide nanoparticles using DNA complexes and may have direct implications for the understanding of biomineralization processes and iron metabolism in living systems.

Synthesis of Iron Oxide Nanoparticles by Thermal Decomposition Approach

An easy onepot reaction for the synthesis of iron oxide nanoparticles is reported. Thermal decomposition of iron acetyl acetonate (Fe(acac)3) in diphenyl ether, in the presence of oleic acid and oleyl amine followed by calcination, leads to the formation of iron oxide nanoparticles. Variation of concentration of the oleyl amine during the synthesis affects the morphology of the iron oxide nanoparticles produced.

In vitro selection of RNA sequences capable of mediating the formation of iron oxide nanoparticles

In vitro selection experiments involving RNA, phagemids, or whole cells can yield biomolecules that bind tightly to or mediate the formation of inorganic materials. Herein we show that RNA sequences that mediate the formation of metal oxide nanoparticles can be isolated from iterative cycles of RNA selection and amplification. In contrast to prior work, the in vitro selection described within was based upon a desired materials property. In order to be isolated from a starting random sequence pool, an RNA sequence was required to mediate the assembly of Co and/or Fe into a solid that responded to a magnetic field. Sequences isolated from this selection were able to mediate the formation of iron oxide nanoparticles containing small amounts of Co under atypical synthesis conditions of temperature and pH.

Free standing thin webs of porous carbon nanofibers of polyacrylonitrile containing iron-oxide by electrospinning

We present for the first time a novel strategy of producing carbon nanofibers (CNFs) using polyacrylonitrile (PAN)-incorporated with iron oxide particles using electrospinning method. The successfully electrospun iron oxide-incorporated PAN thin white web was stabilized in air. Formation of iron oxide nanoparticles resulted in the formation of porous structure on the web. Following heat treatment to the stabilized fibers to about 1000 °C in an N 2 atmosphere resulted in CNFs with specific surface areas, which ranged from 310, 420, and 550 m 2 g − 1 , for PAN containing 1, 2 and 3 wt.% iron oxide, respectively.

Influence of Iron Oleate Complex Structure on Iron Oxide Nanoparticle Formation

The dependence of iron oxide nanoparticle formation on the structure and thermal properties of Fe oleate complexes has been studied using FTIR, elemental analysis, X-ray photoelectron spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM. The combination of FTIR, elemental analysis, and DSC allowed us to reveal differences between Fe oleate structures for as-synthesized and postsynthesis treated (drying and extraction with polar solvents) compounds. As-synthesized Fe oleate was found to contain a significant fraction of oleic acid, which works as a modifier altering the decomposition process and as an extra stabilizer during iron oxide nanoparticle formation. The thermal treatment of as-synthesized Fe oleate at 70 °C leads to removal of the crystal hydrate water and dissociation of oleic acid dimers, leading to a more thermally stable iron oleate complex whose final decomposition occurs at about 380 °C. Extraction of...

Iron hydroxide nanoparticles coated with poly(ethylene glycol)-poly(aspartic acid) block copolymer as novel magnetic resonance contrast agents for in vivo cancer imaging

PEG-coated β-FeOOH nanoparticles were prepared through electrostatic complex formation of iron oxide nanoparticles with poly(ethylene glycol)-poly(aspartic acid) block copolymer [PEG-P(Asp)] in distilled water. By dynamic light scattering (DLS) measurement, the nanopaticle size was determined to be 70 nm with narrow distribution. The FT-IR and zeta potential experimental results proved that PEG-PAsp molecules bound to the surface of the iron oxide nanoparticles via the coordination between the carboxylic acid residues in the PAsp segment of the block copolymer and the surface Fe of the β-FeOOH nanoparticles. The PEG-coated nanoparticles revealed excellent solubility and stability in aqueous solution as well as in physiological saline. In vivo MRI experiments on tumor-bearing mice demonstrated that the PEG-coated nanoparticles prepared by the current approach achieved an appreciable accumulation into solid tumor, suggesting their potential utility as tumor-selective MRI contrast agents.

Hybrid Polymer Particles with a Protective Shell: Synthesis, Structure, and Templating

The development of hybrid polymer particles formed by the hydrolytic condensation of octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride (ODMACl) and the trisodium salt of the triacetic acid N-(trimethoxysilylpropyl)ethylenediamine (TANED) along with self-assembling with nonionic poly(ethylene glycol) (PEG) based surfactants containing a hydrophobic octadecyl tail (Brij) have been studied using liquid and solid-state NMR, dynamic light scattering (DLS), transmission electron microscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS). On the basis of DLS and NMR data, the mechanism of interaction of Brij, ODMACl, and TANED molecules in an aqueous solution has been suggested. The influence of the PEG chain length on the ability of surfactants to stabilize polymer particles has been established. The combination of DSC and XRD assessed the crystallinity and thermal properties of self-assembled hybrid materials in the solid state, while SAXS studies revealed that their morphology strikingly depends on the PEG chain length and reaction conditions determining the degree of Brij incorporation and the structure of the Brij−ODMACl complex. Because of the protective PEG shell, the hybrid polymer particles were successfully used as soluble templates for the formation of iron oxide nanoparticles.

Synthesis of iron oxide nanocomposites using layered double hydroxides

In the present work, an original method for the preparation of oxide nanostructured materials is discussed. The method is based on chemical modification of anion-substituted layered double hydroxides (LDH). It combines the simplicity of chemical methods and the possibility to prepare nanostructures directly in the matrix. During chemical reactions of anions in the interlayer space of LDHs, the reaction zone is spatially constrained by the hydroxide layers, giving rise to the conditions similar to those in 2D nanoreactors, such as Langmuir–Blodgett films and self-assembling monolayers. It was found that chemical modification of intercalated LDHs results in the formation of iron oxide nanoparticles with different morphology and composition (α-Fe2O3, γ-Fe2O3), depending on the composition of initial precursors and conditions of chemical modifications. Obtained nanostructures were investigated by X-ray diffraction, TEM and Mossbauer spectroscopy.

Synthesis and Characterization of Iron Oxide Nanostructured Particles in Na–Y Zeolite Matrix

Formation of iron oxide nanoparticles within the internal cages of Na–Y zeolites was investigated. Sodium ions within the zeolites were replaced with iron(II) ions. Elemental composition studies showed a significant amount of iron in the exchanged sample. NaOH and dropwise additions of H2O2 at 60 °C triggered formation of zeolite–iron oxide systems. X-ray diffraction (XRD) patterns showed diminishing zeolite peaks along with evolution of peaks corresponding to γ-Fe2O3 and α-Fe2O3 with increasing NaOH concentration. Morphological changes from hexagonal-shaped zeolite to clusters of fine particles were observed under scanning electron microscope. Particles with about 15-nm diameter were detected by transmission electron microscopy. γ-Fe2O3 crystallites of 13.4 nm were determined from the broadening of XRD peaks. The magnetization curves of samples (precipitated using NaOH with concentrations of 2.0 M and above) showed absence of hysteresis and passed through the origin, indicating the particles are superparamagnetic. Gas adsorption–desorption measurement of the system precipitated with 2.0 M NaOH revealed a 26% increase in its specific surface area, indicating the presence of nanometer-sized particles within the zeolites.

Delivery of Catalytic Metal Species onto Surfaces with Dendrimer Carriers for the Synthesis of Carbon Nanotubes with Narrow Diameter Distribution

Polyamidoamine (PAMAM) dendrimers are used as carriers to deliver complexed Fe(III) ions uniformly onto silicon oxide substrates for the formation of iron oxide nanoparticles with a narrow diameter in the range of 1−2 nm. Chemical vapor deposition (CVD) synthesis with these nanoparticles affords single-walled carbon nanotubes (SWNTs) with a diameter distribution in the range of 1−2 nm, much narrower than that for SWNTs grown from commonly used powder-supported catalyst (1−5 nm) and from artificial ferritin derived nanoparticles (1−3 nm). Thus, the current work represents a step further toward the synthesis of monodispersed SWNTs via the approach of chemically controlling the formation of discrete catalyst nanoparticles.

Influence of the silica based matrix on the formation of iron oxide nanoparticles in the Fe2O3–SiO2 system, obtained by sol–gel method

Composite iron oxide–SiO2 materials were prepared by a sol–gel method starting with two types of precursors, tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS), as the SiO2 source. As the iron source a soluble Fe2+ salt, mainly Fe(SO4)2·7H2O, was used, the iron oxides were generated during the sol–gel process. The amorphous gels obtained were thermally treated up to 1000 °C in order to obtain iron oxides with different structures and grain size. The initial gels and the thermally treated samples were characterised by DTA/TGA analysis, DR-UV–VIS and IR-spectroscopy, EPR measurements, transmission electron microscopy (TEM) and BET surface area methods. The matrices obtained from the precursors play a major role in the evolution of the process. In both cases the initial gels are amorphous. In the non-porous matrix obtained by thermal treatment using methyltriethoxysilane (MTEOS), the tendency for crystallisation increases, and the iron oxide particle size is increased.

Green Synthesis and Characterization of Antibacterial Studies by Iron Oxide Nanoparticles using Carica papaya Leaf Extract

In present years, the synthesis of iron oxide nanoparticles (IONPs) has established excessive potential in biological applications due to their non-toxic role in biological systems, biocompatibility, and biodegradability. Ongoing research efforts focused on IONPs in the expansion of novel technologies as they can be synthesized with surface modification. Here we have studied the antibacterial effects of IONPs which were synthesized effectively through a green synthesis route by using leaf extract of the Carica papaya plant. The formation of IONPs was confirmed by the color change. The crystallinity of IONPs was determined by XRD and the morphology by using SEM, which showed spherical particles of well-dispersed size. The absorption peak was determined by UV–vis spectroscopy at 390 nm. Average particle size distribution was obtained at 56 nm using PSA. FL spectroscopy indicated the higher emission wavelength by redshift at 641.6 nm. TGA showed that the IONPs are thermally stable up to 200⁰C with no decomposition. The outcome would pave a way for utilizing IONPs for better biomedical application.