Characterization of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized by various methods

Microwave-induced combustion with glycine, CTAB-assisted hydrothermal process with NaOH and NH3, EDTA assisted-hydrothermal methods have been applied to prepare NiFe₂O₄ nanoparticles for the first time. Structural and magnetic properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmison electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and electron spin resonance spectrometry (EPR). TEM measurements showed that morphology of the product depends on the synthesis method employed. The average cystallite size of NiFe₂O₄ nanoparticles was in the range of 14–59 nm as measured by XRD. The uncoated sample (Method A) had an EPR linewidth of 1973 Oe, the coated samples reached lower values. The magnetic dipolar interactions existing among the Ni ferrite nanoparticles are reduced by the coatings, which could cause the decrease in the linewidth of the EPR signals. Additionally, the linewidth increases with an increase in the size and the size distribution of nanoparticles.     

Nano-Architecture of Facetted NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/(Ni,Fe)O Particles Produced by Induction Plasma

Facetted nickel ferrite (NiFe₂O₄) and bunsenite [(Ni,Fe)O] nanocrystals were grown from the decomposition of iron and nickel nitrate precursors using an inductively coupled plasma reactor. The full range of the two-phase region of the Fe₂O₃–NiO pseudo-equilibrium phase diagram was investigated by producing nanopowders with bulk Ni/(Ni + Fe) ratios of 0.33, 0.4, 0.5, 0.75 and 1.0. A Ni-poor [Ni/(Ni + Fe) ≤ 0.5] precursor solution produced truncated octahedron nanocrystals, whereas nanocubes were obtained at higher ratios [Ni/(Ni + Fe) ≈ 1]. In both cases, it is shown that the nanocrystals adopt a morphology close to the Wulff shape of the crystalline system (spinel and NaCl, respectively). As the bulk Ni/(Ni + Fe) ratio increases from 0.33 (the stoechiometric composition of nickel ferrite), bunsenite is epitaxially segregated on the {110} and {111} facets of nickel ferrite, while leaving the NiFe₂O₄ {100} facets exposed. A precursor solution at a Ni/(Ni + Fe) ratio of 0.75 gave an (Ni,Fe)O-rich nanopowder with a random and irregular interconnected morphology. The structure of these nanocrystals can be understood in terms of their thermal history in the plasma reactor. These results highlights the possibility of producing organized multi-phased nanomaterials of binary systems having two phases stable at high temperatures, using a method known to be easily scalable.     

Comparative study of the synthesis of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> in silica through the polymerized complex route of the sol–gel method

In this work the synthesis of CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors, without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe₂O₄ and NiFe₂O₄ in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C.     

CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles structural and magnetic stability relative to ball milling

The combustion method has been utilized to generate cobalt spinel ferrite nanoparticles. The generated nanoparticles were ball milled for different times. Physical and chemical properties of the nanoparticles were characterized by X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). Crystalline structure of the nanoparticles was stable after ball milling. FTIR showed that oxygen-metal bonding was stronger after ball milling. Moreover, the ball milled nanoparticles magnetically were harder than the nanoparticle without ball milling.     

Non-isothermal decomposition kinetics of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized using egg white solution route

The thermal decomposition kinetics of nickel ferrite (NiFe₂O₄) precursor prepared using egg white solution route in dynamical air atmosphere was studied by means of TG with different heating rates. The activation energy (E _α) values of one reaction process were estimated using the methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS), which were found to be consistent. The dependent activation energies on extent of conversions of the decomposition reaction indicate “multi-step” processes. XRD, SEM and FTIR showed that the synthesized NiFe₂O₄ precursor after calcination at 773 K has a pure spinel phase, having particle sizes of ~54 ± 29 nm.     

2-pyrrolidone - capped Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocrystals

Water-soluble Mn₃O₄ nanocrystals have been prepared through thermal decomposition in a high temperature boiling solvent, 2-pyrrolidone. The final product was characterized with XRD, SEM, TEM, FTIR and Zeta Potential measurements. Average crystallite size was calculated as ∼15 nm using XRD peak broadening. TEM analysis revealed spherical nanoparticles with an average diameter of 14±0.4 nm. FTIR analysis indicated that 2-pyrrolidone coordinates with the Mn₃O₄ nanocrystals only via O from the carbonyl group, thus confining their growth and protecting their surfaces from interaction with neighboring particles.      

Synthesis and characterization of Co<Subscript>0.8</Subscript>Zn<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Cobalt zinc ferrite, Co_0.8Zn_0.2Fe₂O₄, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co_0.8Zn_0.2Fe₂(C₄H₂O₄)₃·6N₂H_4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.     

Superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles Decorated Multiwalled Carbon Nanotubes: Preparation via Cyclic Microwave Approach and Their Drug Release Behavior

Superparamagnetic Fe₃O₄ nanoparticles decorated multiwalled carbon nanotubes were synthesized by cyclic microwave method and the effect of different reaction parameters on the products were also investigated. The as synthesized products were characterized by XRD, TEM, SEM, EDS, FT-IR, VSM, and Uv–Vis spectroscopy. It was observed that precursors’ concentration ratio had great effect on the particle size and decorating quality. Also the effect of the other parameters including irradiation power and time on product size and uniformity of the product were also investigated. The best products with desired particle size distribution obtained when irradiation power and reaction time were 900 W and 6 min, respectively. Aspirin and acetaminophen were applied as a model drug and the drug release behavior of the composite was investigated. It was observed that the drug discharge was highly dependent to the pH and can be tuned by applying magnetic field.     

Physical and chemical properties of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles prepared by combustion and ultrasonic bath methods

The combustion and ultrasonic bath methods have been utilized to generate nickel spinel ferrite nanoparticles. Physical and chemical properties of generated nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). Between the nanoparticles generated by mentioned methods, there were differences in size, oxygen-metal bonding, and magnetic properties which have been investigated in the work.     

Nickel and cobalt ferrites nanoparticles: synthesis,study of magnetic properties and their use as magnetic adsorbent for removing lead(II) ion

Nano-sized nickel ferrite (NiFe₂O₄) and cobalt ferrite particles (CoFe₂O₄) were successfully synthesized using a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscope, Fourier transform infrared spectrometer, energy dispersive X-ray spectroscopy, vibrating sample magnetometer and transmission electron microscope have been used to characterize and study the as-synthesized NiFe₂O₄ and CoFe₂O₄ products. The results showed that the average size of the nickel and cobalt ferrite nanoparticles is smaller than 10 and 100 nm, respectively. The results of magnetic measurement showed that the synthesized NiFe₂O₄ and CoFe₂O₄ nanoparticles were superparamagnetic and soft ferromagnetic materials, respectively. Study of adsorption behavior showed that these nanoparticles can act as a good adsorbent for removing Pb²⁺.     

Preparation,spectroscopic and thermal analysis of hexa-hydrazine nickel cobalt ferrous succinate precursor and study of solid-state properties of its nanosized thermal product,Ni<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Nickel cobalt ferrite, Ni_0.5Co_0.5Fe₂O₄, has been prepared by precursor combustion technique from hexa-hydrazine nickel cobalt ferrous succinate precursor. The precursor was characterized by chemical analysis, CHNS analysis, infrared spectroscopy, TG–DTA and mass loss studies. The thermal data show how the precursor decomposes in four steps to give stable ferrite phase. The precursor decomposes autocatalytically once initially ignited, to give the ‘as-prepared’ nano-spinel ferrite. The X-ray diffraction analysis reveals single cubic spinel phase structure. The infrared measurements between 4000 and 350 cm^?1 confirmed the intrinsic cation vibrations of the spinel structure. The SEM image clearly shows the nanosized nature of the ferrite. The dielectric constant and loss tangent are found to decrease with increase in frequency which is due to Maxwell–Wagner interfacial polarization. The loss tangent shows a relaxation peak at ~1 kHz. The variation of DC electrical resistivity with temperature indicates semiconductor behaviour. The temperature- and field-dependent magnetization data of ‘as-prepared’ ferrite reveal that the lattice has either a canted or partially misaligned spin structure due to the nanosized nature of the ferrite.     

MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles with excellent catalytic activity in thermal decomposition of ammonium perchlorate

MnCo₂O₄ spinel nanoparticles (NPs) have been prepared using Aloe vera gel solution. The characterization of prepared spinel was performed applying Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron spectroscope, scanning electron microscope and dynamic light scattering. The results manifested that the prepared nanoparticles were mainly spherical plus minor agglomeration with average size distribution between 35 and 60 nm. The catalytic activity of the prepared nanoparticles upon thermal degradation of ammonium perchlorate (AP) was evaluated applying differential scanning calorimetry and thermogravimetry instruments. MnCo₂O₄ nanoparticles increased the released heat of AP from 450 to 1480 J g^?1 and decreased the decomposition temperature from 420 to 293 °C. The kinetic parameters obtained from Kissinger methods showed that the activation energy of AP thermal decomposition in the presence of MnCo₂O₄ NPs considerably decreased. Also, a mechanism has been proposed in the presence of catalyst for the process of thermal decomposition of AP.     

Microwave sintering of nickel ferrite nanoparticles processed via sol–gel method

Magnetic nickel ferrite (NiFe₂O₄) was prepared by sol–gel process and calcined in the 2.45 GHz singlemode microwave furnace to synthesize nickel nanopowder. The sol–gel method was used for the processing of the NiFe₂O₄ powder because of its potential for making fine, pure and homogeneous powders. Sol–gel is a chemical method that has the possibility of synthesizing a reproducible material. Microwave energy is used for the calcining of this powder and the sintering of the NiFe₂O₄ samples. Its use for calcination has the advantage of reducing the total processing time and the soak temperature. In addition to the above combination of sol–gel and microwave processing yields to nanoscale particles and a more uniform distribution of their sizes. X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and vibrating sample magnetometer were carried out to investigate structural, elemental, morphological and magnetic aspects of NiFe₂O₄. The results showed that the mean size and the saturation magnetization of the NiFe₂O₄ nanoparticles are about 30 nm and 55.27 emu/g, respectively. This method could be used as an alternative to other chemical methods in order to obtain NiFe₂O₄ nanoparticles.     

Phytochemical analysis and Enzyme Inhibition Assay of Aerva javanica for Ulcer

Background

Nickel ferrite, a kind of soft magnetic materials is one of the most attracting class of materials due to its interesting and important properties and has many technical applications, such as in catalysis, sensors and so on. In this paper the synthesis of NiFe₂O₄ nanoparticles by the hydrothermal method is reported and the inhibition of surfactant (Glycerol or Sodium dodecyl sulfate) on the particles growth is investigated.

Methods

For investigation of the inhibition effect of surfactant on NiFe₂O₄ particles growth, the samples were prepared in presence of Glycerol and Sodium dodecyl sulfate. The X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and inductively coupled plasma atomic emission spectrometer (ICP-AES) techniques were used to characterize the samples.

Results

The results of XRD and ICP-AES show that the products were pure NiFe₂O₄ and also nanoparticles grow with increasing the temperature, while surfactant prevents the particle growth under the same condition. The average particle size was determined from the Scherrer's equation and TEM micrographs and found to be in the range of 50-60 nm that decreased up to 10-15 nm in presence of surfactant. The FT-IR results show two absorption bands near to 603 and 490 cm^-1 for the tetrahedral and octahedral sites respectively. Furthermore, the saturated magnetization and coercivity of NiFe₂O₄ nanoparticles were in the range of 39.60 emu/g and 15.67 Q_e that decreased for samples prepared in presence of surfactant. As well as, the nanoparticles exhibited a superparamagnetic behavior at room temperature.

Conclusions

Nanosized nickel ferrite particles were synthesized with and without surfactant assisted hydrothermal methods. The results show that with increasing of temperature, the crystallinity of nanoparticles is increased. In the presence of surfactants, the crystallinity of NiFe₂O₄ nanoparticles decreased in comparison with surfactant- free prepared samples. All of the nickel ferrite nanoparticles were superparamagnetic at room temperature.

Graphical abstract

     

Synthesis and Characterization of the Superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Ag Nanocomposites

The study of superparamagnetic Fe₃O₄/Ag nanocomposites have received great research attention due to their wide range of potential applications in biomedicine. In this report, an easy microemulsion reaction was employed to synthesis Fe₃O₄/Ag nanocomposites with self-aggregated branch like nanostructures. The Fe₃O₄ nanoparticles were initially prepared and subsequently AgNO₃ was reduced as Ag by chemical reduction method. The results showed that the average size of the Fe₃O₄/Ag nanocomposites were in the range of 10 ± 2 nm. These nanoparticles were self-aggregated as a branch like nanostructure. The optical properties of Fe₃O₄ nanoparticles were modified with surface plasmon resonance of Ag nanoparticles. The observed saturation magnetization of superparamagnetic Fe₃O₄/Ag nanocomposites were 40 emu/g.     

Effect of active impurities on the condensation of nanoparticles from supersaturated carbon vapor in the combined laser photolysis of C<Subscript>3</Subscript>O<Subscript>2</Subscript> and H<Subscript>2</Subscript>S

The effect of active H₂S, HS^·, and atomic hydrogen impurities on the condensation of highly supersaturated carbon vapor obtained in the combined laser photolysis of a mixture of C₃O₂ and H₂S diluted with argon was studied. The concentrations of carbon vapor, HS^·, and atomic hydrogen obtained in the laser photolysis of the mixture were determined using the absorption cross sections of C₃O₂ and H₂S molecules measured in this work and the measured amount of absorbed laser radiation. The time profiles of the sizes of growing nanoparticles synthesized in C₃O₂ + Ar and C₃O₂ + H₂S + Ar mixtures were measured using the laser-induced incandescence (LII) method. An improved LII model was developed, which simultaneously took into account the heating and cooling of nanoparticles and the temperature dependence of the thermophysical properties of nanoparticles, as well as the cooling of nanoparticles by evaporation and thermal emission. The size distributions of carbon nanoparticles formed in the presence and absence of active impurities were determined with the use of a transmission electron microscope. The final average size of carbon nanoparticles was found to decrease from 12 to 9 nm upon the addition of H₂S to the system, whereas the rate of nanoparticle growth decreased by a factor of 3, and the properties of nanoparticles changed. In particular, the translational energy accommodation coefficient for Ar molecules at the surface of carbon nanoparticles was found to decrease from 0.44 to 0.30. A comparison of the calculated total carbon balance at the early stage of nanoparticle formation with experimental data demonstrated that the reaction C + H₂S → HCS^· + H, which removes a portion of carbon vapor from the condensation process, has a determining effect on the carbon balance in the system. It was found that HS^· and atomic hydrogen affect the carbon balance in the system only slightly. Thus, the experimentally observed decrease in the rate of nanoparticle growth and in the sizes of nanoparticles can be explained by a decrease in the concentration of free carbon upon the addition of H₂S molecules to the system.     

Nickel ferrite nanoparticles synthesis from novel fumarato-hydrazinate precursor

Nickel ferrite is technologically important magnetic material extensively used in high frequency applications such as microwave device due to its high resistivity and sufficiently low losses. It also finds application in the ferrofluids technology. Therefore, ultrafine nickel ferrite was prepared by autocatalytic combustion of novel nickel ferrous fumarato-hydrazinate precursor. The precursor was characterized by IR, AAS, TG and DTA, and a chemical formula of NiFe₂(C₄H₂O₄)₃·6N₂H₄ was fixed. This precursor once ignited with a burning splinter at room temperature, glows and the glow spreads over the entire bulk completing the autocatalytic combustion of the precursor to ultrafine ferrite. The single phase formation of ultrafine nickel ferrite was confirmed by XRD, IR spectra and TEM. The average particle size of the ultrafine ferrite was found to be ∼20 nm by TEM. The observed lower value of saturation magnetization for nickel ferrite was due to the superparamagnetic nature of the particles, which increased with the increasing sintering temperature. The ultrafine nickel ferrite was then sintered at 1000°C for 5 h and was characterized by XRD, IR spectra, SEM and TEM. The variation of resistivity, Seebeck coefficient and a.c. susceptibility as a function of temperature was measured for NiFe₂O₄ and the results are discussed.     

H<Subscript>3</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript> immobilized chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a novel efficient,green and recyclable nanocatalyst in the synthesis of pyrano-pyrazole derivatives

A novel nanomagnetic composite heteropolyacid immobilized chitosan/Fe₃O₄ was prepared via a facile one-pot synthetic approach. This magnetically recoverable nanocatalyst, H₃PMo₁₂O₄₀/chitosan/Fe₃O₄ (PMo/chit/Fe₃O₄), was fully characterized by XRD, FTIR, SEM and EDX analysis methods. A rapid, efficient and the chemoselective synthesis of different pyrano-pyrazole derivatives was achieved in excellent yields via a one-pot four-component reaction in the presence of catalytic amount of PMo/Chit/Fe₃O₄.     

Synthesis and characterization of Ni<Subscript>0.6</Subscript>Zn<Subscript>0.4</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nano-particles obtained by auto catalytic thermal decomposition of carboxylato-hydrazinate complex

Ni_0.6Zn_0.4Fe₂O₄ nano-particles have been synthesized by self-propagating auto-combustion of nickel zinc ferrous fumarato-hydrazinate complex. The precursor complex has been characterized by chemical analysis, IR, AAS, thermal analysis and isothermal mass loss studies. The precursor on ignition undergoes self-propagating auto combustion to give Ni_0.6Zn_0.4Fe₂O₄. The X-ray diffraction studies confirmed the single phase formation of nano-size ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. TEM observation showed the average particle size to be 20 nm. Infrared and magnetization studies were also carried out on the ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. The lower value of saturation magnetization and higher Curie temperature of ‘as synthesized’ ferrite also hint at the nano size nature.     

Nonstoichiometric Zn Ferrite and ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Composite Spheres: Preparation,Magnetic Properties,and Chromium Removal

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe₂O₄/Fe₂O₃ composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe₂O₄/Fe₂O₃ composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe₂O₄/Fe₂O₃ composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe₂O₄/Fe₂O₃ composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe₂O₃,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr⁶⁺ adsorption property than ZnFe₂O₄/Fe₂O₃ composites.