Aqueous Co-precipitation Research Articles

Effect of Temperature on Fe<sub>3</sub>O<sub>4</sub> Magnetic Nanoparticles Prepared by Coprecipitation Method

The Fe3O4 magnetic nanoparticles obtained by the aqueous coprecipitation method are characterized systematically using scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. These magnetic nanoparticles are spheric, dispersive, and have average grain size of 50 nm. The size and magnetic properties of Fe3O4 nanoparticles can be tuned by the reaction temperature. All samples exhibit high saturation magnetization (Ms=53.4 emu·g-1) and superparamagnetic behavior with a block temperature (TB) of 215K. These properties make such Fe3O4 magnetic nanoparticles worthy candidates for the magnetic carriers of targeted-drug or gene therapy in future.

In vitro application of Mn-ferrite nanoparticles as novel magnetic hyperthermia agents.

Manganese ferrite nanoparticles were synthesized by a facile, low-cost, environmentally friendly and high yield methodology based on the aqueous co-precipitation of proper salts. Firstly, structural, morphological and magnetic characterization schemes were performed to determine crucial factors for optimizing their heating potential, such as size, polydispersity, saturation magnetization and coercivity. In an effort to simulate the in vivo environment of animal tissue phantoms and study the thermal heating effects resulting from Brownian motion and hysteresis losses, nanoparticles at various concentrations were embedded in aqueous media of varying agar concentration. During the in vitro application healthy cells (primary bone marrow-derived osteoblasts and 3T3-L1 fibroblast-like preadipocytes) and human osteosarcoma Saos-2 cells were incubated with manganese ferrite nanoparticles. The heating profile of the particles was studied at different concentrations and in correlation with their potential cytotoxic effect. Our results revealed concentration dependent cytotoxicity profile and uptake efficiency together with variable specific loss power values yet with fast thermal response, opening novel pathways in material selection as hyperthermia agents.

The polymerisation of oligo(ethylene glycol methyl ether) methacrylate from a multifunctional poly(ethylene imine) derived amide: a stabiliser for the synthesis and dispersion of magnetite nanoparticles

A facile synthetic route to poly(ethylene imine)-graft-poly(oligo(ethylene glycol methyl ether)) (PEI-graft-POEGMA) functionalised superparamagnetic magnetite nanoparticles is described. The polymerisation of OEGMA from a model molecular amide demonstrated the feasibility of POEGMA synthesis under mild ATRP conditions (20 °C in ethanol) albeit with low initiator efficiencies. DFT studies suggest that the amide functionality is intrinsically of lower activity than ester functional monomers and initiators for atom transfer polymerisation (ATRP) as a consequence of higher bond dissociation energies and bond dissociation free energies (BDFE). However these studies further highlighted that use of an appropriate solvent could reduce the free energy of dissociation thereby reducing the relative difference in BDFE between the ester and amide groups. A commercial branched PEI sample was functionalised by reaction with 2-bromo-2-methylpropanoyl bromide giving an amide macroinitiator suitable for the atom transfer radical polymerisation (ATRP) of oligo(ethylene glycol methyl ether) methacrylate. The resulting PEI-graft-POEGMA copolymers were characterised by SEC, FT-IR and 1H and 13C NMR spectroscopy. PEI-graft-POEGMA coated magnetite nanoparticles were synthesised by a basic aqueous co-precipitation method and were characterised by transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometry and dynamic light scattering. These copolymer coated magnetite nanoparticles were demonstrated to be effectively stabilised in an aqueous medium. Overall the particle sizes and magnetic and physical properties of the coated samples were similar to those of uncoated samples.

Effect of pH on structural and magnetic properties of nanocrystalline Y3Fe5O12 by aqueous co-precipitation method

The Y3Fe5O12 (YIG) nanopowders were synthesised at different pH using co-precipitation method. The effect of pH on the phase formation of YIG is characterised using XRD, TEM, FTIR and TG/DTA. From the Scherer formula, the particle sizes of the powders were found to be 13, 19 and 28 nm for pH = 10, 11 and 12 respectively. It is found that as the pH of the solution increase the particle size is also increases. It is also clear from the TG/DTA curves that as the pH is increasing the weight losses were found to be small. The nanopowders were sintered at 600, 700, 800 and 900°C for 5 h using conventional sintering method. The phase formation is completed at 800°C/5 h which is correlated with TG/DTA. The average grain size of the samples is found to be ∼161 nm. The high values of Ms = 23 emu g−1 and Hc = 22 Oe were recorded for the sample sintered at 900°C.

Y-a-t-il une association entre la sévérité de la déformation de type CAM dans le conflit fémoro-acétabulaire et l’altération du cartilage acétabulaire ?

The effect of co-joint additions of Y and Dy on the electrical conductivity of ceria ceramics was studied by impedance spectroscopy. Powder materials were synthesized by aqueous coprecipitation to obtain Ce1−x(Y0.5Dy0.5)xO2−δ with 0 ≤ x ≤ 0.15. Sintering of powder compacts was carried out at 1450 °C for 4 h. The main results show that high densification (∼95% of theoretical value) was attained for all compositions. Raman spectroscopy results evidenced the solid solution formation among cerium, yttrium and dysprosium. The electrical conductivity of sintered specimens varies with the total dopant content. A maximum conductivity value was obtained for a lower dopant content considering the behaviour of singly doped ceramics. Moreover, sintered specimens with the same total dopant content exhibit similar electrical conductivity values suggesting that the concentration of oxygen vacancies play a major role in the conduction process of co-doped ceramics.

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM−1s−1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis.PACS75.75.Fk, 78.67.Bf, 61.46.Df

Band engineering of Cu2+ doped In2xZn3(1−x)S3 solid solution with high photocatalytic activity for H2 production under visible light

A facile aqueous co-precipitation method is successfully introduced to synthesize ZnS–In2S3 solid solution (labeled In2xZn3(1−x)S3, x = 0–1) and Cu2+ doped In1.4Zn0.9S3 (x = 0.7) solid solution (labeled Cu(y)/In1.4Zn0.9S3, y = 0–4%). Their band gap energies are dependent on the compositional x and y values. The photocatalytic hydrogen generation rate can be remarkably improved to 438 μmol h−1 for Cu(1%)/In1.4Zn0.9S3 solid solution, in comparison with 79 μmol h−1 for un-doped In1.4Zn0.9S3 solid solution. It is suggested that the coupling of the two traditional band engineering strategies of making solid solution and metal ion doping is beneficial to obtain an appropriate conduction band position and effective charge separation of Cu2+ doped In2xZn3(1−x)S3 solid solution, thus improve the photocatalytic activity. This work provides a new opportunity to design novel efficient photocatalysts for water splitting into hydrogen.

Synthesis of M–Nd doped Fe3O4 nanoparticles (M = Co, Ce, Cr, Ni) with tunable magnetic properties

Magnetic nanoparticles were prepared by the aqueous co-precipitation method. The magnetic nanoparticles obtained were characterized systematically through the use of an X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and a vibrating sampling magnetometer (VSM). The results revealed that the magnetic nanoparticles were spherical shaped with inverse spinel structure. The size of Fe3O4 and Nd-Co doped Fe3O4 magnetic nanoparticles were approximately 15 nm. Magnetic measurement revealed that the nanoparticles were super paramagnetic at room temperature. It was found that the magnetic response of the Fe3O4 increased when it was doped with Nd3+ and Co2+. However, the magnetic response of the Fe3O4 decreased when it was doped with Nd3+ or Ce3+ or Cr3+or Ni2+. KEYWORDS: Fe3O4, Magnetic nanoparticles, Superparamagnetic, Magnetite, Fe3O4 doped Bull. Chem. Soc. Ethiop. 2013, 27(1), 49-56.DOI: http://dx.doi.org/10.4314/bcse.v27i1.5

PH- and Dopant-Dependent CdMoO4:Mn Nanocrystals: Luminescence and Magnetic Properties

CdMoO(4):Mn nanocrystals with a tetragonal crystal structure were prepared by aqueous coprecipitation method at a low temperature of 2 °C under different pH values. The size of the CdMoO(4):Mn nanocrystals of spherical morphology increases with the Mn dopant concentration from 35 to 55 nm for pH = 4. The morphology could be tuned from nanocrystals to microstructures consisting of smaller nanoparticles by the Mn concentration when the pH value of the precursor was increased to 8. The thermal stability of the luminescence and magnetic properties of the Mn-doped samples also depend on the pH and the doping level. The effects of the pH and dopant on the luminescence and magnetic properties, including magnetic susceptibility and electron paramagnetic resonance, were investigated. This approach contributes to better understanding of aqueous chemistry methods to control the growth of nanocrystals.

Synthesis of tetragonal mackinawite-type FeS nanosheets by solvothermal crystallization

Mackinawite, a metastable 1:1 compound of iron and sulfur that adopts an anti-PbO-type structure, is of interest because of its relationship to known iron chalcogenide superconductors, as well as its biogeochemical relevance. Colloidal nanosheets of mackinawite-type FeS were synthesized by first generating an amorphous Fe–S precursor via the aqueous room-temperature co-precipitation of Fe2+ and S2−, then solvothermally crystallizing it in ethylene glycol at 200°C in an autoclave. The product is highly crystalline, with lattice constants of a=3.674(3)Å and c=5.0354(3)Å. The nanosheets, with their surface normal oriented along the [001] direction, are irregularly faceted with edge lengths that range from 100nm to over 1μm and average thicknesses of approx. 30nm. The samples showed a ferromagnetic background signal with no evidence of superconductivity.

Permeability spectra of Co2Z hexaferrite compacts produced via a modified aqueous co-precipitation technique

Co2Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values (∼1GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co2Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co2Z hexaferrite particles, at ∼24g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5–2um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.

In situ synthesis of magnesium-substituted biphasic calcium phosphate and in vitro biodegradation

In situ preparation of magnesium (Mg) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added magnesium were varied with the calcium in order to obtain constant (Ca+Mg)/P ratios of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized magnesium substituted BCP powders. The results have shown that substitution of magnesium in the calcium deficient apatites revealed the formation of biphasic mixtures of different HAp/β-TCP ratios after heating at 1000°C. The ratios of the formation of phase mixtures were dependent on the content of magnesium. After immersing in Hanks’ balanced salt solution (HBSS) for 1 week, 1wt% magnesium substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. On the other hand, in the case of pure BCP powders, the formation of new precipitates was detected after immersion in HBSS for 2 weeks. On the basis of these results, magnesium substituted BCP could be able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. In addition, the retention time to produce the new apatite phase in implantation operation for the BCP powder could be controlled by the amount of magnesium substitution.

Superparamagnetic MFe2O4 (M = Fe, Co, Mn) Nanoparticles: Tuning the Particle Size and Magnetic Properties through a Novel One-Step Coprecipitation Route

Superparamagnetic ferrite nanoparticles (MFe2O4, where M = Fe, Co, Mn) were synthesized through a novel one-step aqueous coprecipitation method based on the use of a new type of alkaline agent: the alkanolamines isopropanolamine and diisopropanolamine. The role played by the bases on the particles’ size, chemical composition, and magnetic properties was investigated and compared directly with the effect of the traditional inorganic base NaOH. The novel MFe2O4 nanomaterials exhibited high colloidal stability, particle sizes in the range of 4–12 nm, and superparamagnetic properties. More remarkably, they presented smaller particle sizes (up to 6 times) and enhanced saturation magnetization (up to 1.3 times) relative to those prepared with NaOH. Furthermore, the nanomaterials exhibited improved magnetic properties when compared with nanoferrites of similar size synthesized by coprecipitation with other bases or by other methods reported in the literature. The alkanolamines were responsible for these achievem...

Nanocomposites Based on Technical Polymers and Sterically Functionalized Soft Magnetic Magnetite Nanoparticles: Synthesis, Processing, and Characterization

This experimental study deals with the synthesis, processing, and characterization of highly filled nanocomposites based on polyvinyl butyral/magnetite (PVB/Fe3O4) and polymethylmethacrylate/magnetite (PMMA/Fe3O4). The nanoparticles are synthesized in an aqueous coprecipitation reaction and show a single particle diameter of approximately 15 nm. The particles are sterically functionalized and covered by PVB and PMMA in a spray drying process. The synthesized compound particles are further processed by injection molding to test specimens with filler contents up to 14.5 vol.‐%. PVB and PMMA specimen are processed as a reference as well. The distribution of the nanoparticles is characterized by microscopy. Besides a minor number of agglomerates and aggregates the nanoparticles are distributed homogeneously in the PVB composites. Furthermore, the injection molded specimens are characterized with regard to their thermal degradation, polymer structure, and their mechanical and magnetic properties. The presence of nanoparticles capped with ricinoleic acid shows significant decrease in degradation temperature and in glass transition temperature of PVB. The degradation temperature of PMMA is increased by adding nanoparticles capped with oleic acid. Dynamic‐mechanical properties as well as the magnetic permeability of PVB and PMMA are improved significantly by adding nanoparticles.

Controlled Synthesis, Characterization and Magnetic Properties of Magnetite (Fe<sub>3</sub>O<sub>4</sub>) Nanoparticles without Surfactant under N<sub>2</sub> Gas at Room Temperature

In this study, magnetite (Fe3O4) nanoparticles were synthesized at room temperature using FeCl3.6H2O (1.28 M), FeCl2.4H2O (0.64 M) and HCl (0.4 M) for preparing a solution as the iron source and NaOH (0.9-1.5 M) for to prepare a solution as the alkali source by the aqueous phase co-precipitation method under vigorous mechanical stirring (450 and 750 rpm) together with N2 gas flowing through the reaction medium during synthesis operation in closed system. The powder samples were characterized by the commonly used techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and BET analyses. SEM was used to observe the morphology and agglomeration state of the powder. Size and morphology of the precipitated crystallites were examined with TEM. The prevalence of functional groups in the synthesized powders was ascertained by FTIR spectroscopy. The pure magnetite and other phases according to processing parameters were observed by XRD analysis. The magnetic properties of magnetite (Fe3O4) nanoparticles were examined using VSM. Finally, the specific surface area of nanoparticles was measured by BET technique. The results indicate that smaller particles can be synthesized by increasing stirring rate and decreasing the NaOH concentration, which in this case corresponded to 35 nm using 0.9 M NaOH at 750 rpm. The VSM analysis showed a saturation magnetization range of (82-96 emu/g) and coercivity of (83-119 Oe) for particles between (35-96 nm) respectively. Also, the highest specific surface area of 40 m2/g was obtained at 0.9 M NaOH at 750 rpm and the smallest value of 15 m2/g at 1.5 M of NaOH at 450 rpm using BET analysis.

In situ synthesis of silicon-substituted biphasic calcium phosphate and their performance in vitro

In situ preparation of silicon (Si) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/ β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added silicon were varied with the phosphor in order to obtain constant Ca/(P+Si) ratios of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized silicon substituted BCP powders. The characterization revealed that the formation of biphasic mixtures of different HAp/ β-TCP ratios was dependent on the content of silicon. After immersing in Hanks' balanced salt solution (HBSS) for 1 week, 3 wt% silicon substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. In the case of 1 wt% silicon substituted BCP powders, the degradation behavior was detected after immersion in HBSS for 3 weeks. On the other hand, silicon unsubtituted BCP powders were not degraded even after that duration. On the basis of these results, silicon substituted BCP is able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. This enhanced reactivity resulted in reduction for the stability of the β-TCP structure due to SiO 4 tetrahedral distortion and disorder at the hydroxyl site when silicon incorporates into BCP.

Aqueous Co-precipitated Ti0.5Sn0.5O2 Nanopowders as Precursors for Dense Spinodally Decomposed Ceramics

Spinodal decomposition in the TiO2–SnO2 system produces TiO2 rich/SnO2 rich nano-wide lamellae. The high density of coherent interfaces is expected to reduce thermal conductivity of the ceramic without blocking electron transport. These semiconductors could therefore be candidates for environmental friendly oxide thermo-electrics. However, dense materials are difficult to obtain by conventional sintering from a mixture of TiO2 and SnO2 powders due to evaporation of tin oxide. The article presents a novel route to produce, by aqueous co-precipitation, Ti0.5Sn0.5O2 nanopowders as precursors for dense ceramics. The nanostructure developed by spinodal decomposition inside the grains of the as obtained dense Ti0.5Sn0.5O2 ceramic is shown to be comparable to that of porous Ti0.5Sn0.5O2 ceramic obtained by conventional method.

Aqueous co-precipitation of Pd-doped cerium oxide nanoparticles: chemistry, structure, and particle growth

Nanoparticles of palladium-doped cerium oxide (Pd–CeO2) have been prepared by aqueous co-precipitation resulting in a single phase cubic structure after calcination according to X-ray diffraction (XRD). Inhomogeneous strain, calculated using the Williamson–Hall method, was found to increase with palladium content, and the lattice contracts slightly, relative to nano-cerium oxide, as palladium content is increased. Moreover, high resolution transmission electron microscopy reveals some instances of defective microstructure. These factors combined imply that palladium is in solid solution with CeO2 in these nanoparticles, but palladium (II) oxide (PdO) peaks in the Raman spectra indicate that solid solution formation is partial and that highly dispersed PdO is present as well as the solid solution. Nevertheless, the addition of palladium to the CeO2 lattice inhibits the growth of the 6% Pd–CeO2 particles compared to pure CeO2 between 600 and 850 °C. Activation energies for grain growth of 54 ± 7 and 79 ± 8 kJ/mol were determined for 6% Pd–CeO2 and pure CeO2, respectively, along with pre-exponential Arrhenius factors of 10 for the doped sample and 600 for pure cerium oxide.

Coprecipitation of 60Co from aqueous solutions with triethylenediamine complexes of d-element nitrates

Formation of complexes of Co2+ with triethylenediamine (CH2-CH2)3N2 (Q) in aqueous solution and coprecipitation of microamounts of 60Co with triethylenediamine complexes of Cu2+, Ni2+, and Zn2+ nitrates were studied. Microamounts of 60Co poorly coprecipitate with triethylenediamine complexes of Cu2+ and Zn2+ nitrates. At practically 100% precipitation of Cu2+ and Zn2+ from solutions in the form of the corresponding complexes, the degree of coprecipitation of 60Co with these complexes does not exceed 15%. With the Ni2+ complexes formed from 10−1 M aqueous solutions at the molar ratios Ni2+: Q = 1 : 1 and 1 : 2, the degree of coprecipitation of 60Co is about 45 and 90%, respectively.

Structure, morphology and magnetic properties ofMg(x) Zn(1 − x)Fe2O4 ferrites prepared by polyol and aqueous co-precipitation methods: a low-toxicity alternative toNi(x)Zn(1 − x)Fe2O4 ferrites

The synthesis and properties ofMg(x)Zn(1 − x)Fe2O4 spinel ferrites as a low-toxicity alternative to the technologically significantNi(x)Zn(1 − x)Fe2O4 ferrites are reported. Ferrite nanoparticles have been formed through boththe polyol and aqueous co-precipitation methods that can be readilyadapted to industrial scale synthesis to satisfy the demand of a variety ofcommercial applications. The structure, morphology and magnetic properties ofMg(x)Zn(1 − x)Fe2O4 were studied as a function of composition and particle size. Scanning electron microscopy images showparticles synthesised by the aqueous co-precipitation method possess a broad size distribution (i.e. ∼ 80–120 nm) with an average diameter of the order of100 nm ± 20 nm and could be produced in high process yields of up to 25 g l − 1. In contrast, particles synthesised by the polyol-based co-precipitationmethod possess a narrower size distribution with an average diameter in the30 nm ± 5 nm range but are limited to smaller yields of ∼ 6 g l − 1. Furthermore, the polyol synthesis method was shown to control average particle size byvarying the length of the glycol surfactant chain. Particles prepared by both methods arecompared with respect to their phase purity, crystal structure, morphology, magneticproperties and microwave properties.