Synthesis and characterization of polyrhodanine/nickel ferrite nanocomposite with an effective and broad spectrum antibacterial activity

Nickel ferrite nanoparticles were successfully synthesized via a co-precipitation approach, and then polyrhodanine/nickel ferrite nanocomposite (PRh/NiFe₂O₄) as an antimicrobial agent was fabricated by a chemical polymerization method. The synthesized NiFe₂O₄ nanoparticles and PRh/NiFe₂O₄ nanocomposite were chemically, magnetically and morphologically characterized using FTIR, FESEM, DLS, VSM and XRD techniques. The FESEM analysis showed that the NiFe₂O₄ nanoparticles had a polygon structure with an average diameter of 50 nm. According to disc diffusion as well as MIC and MBC tests, the PRh/NiFe₂O₄ nanocomposite had better antibacterial effects on killing Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli in comparison with the NiFe₂O₄ nanoparticles.     

Magnetic resonance of the NiFe2O4 nanoparticles in the gigahertz range

We report an adjustable magnetic resonance frequency from 1.45 to 2.54 GHz for NiFe₂O₄ nanoparticles which were prepared by a sol–gel process. X-ray diffraction and scanning electron microscopy results indicate that the samples are polycrystalline nanoparticles, and the size of the particles increases obviously with the thermal treatment temperature. The consequence of the surface composition suggests that the oxygen defects are present in the nanoparticle surface, and this surface magnetic state can show a strong surface anisotropy. With decreasing size of the particle, the surface magnetic effect is predominant, resulting in an increase of resonance frequency for NiFe₂O₄ nanoparticles. This finding provides a new route for NiFe₂O₄ materials that can be used in the gigahertz range.     

Effect of surfactants (PVB/EDTA/CTAB) assisted sol-gel synthesis on structural,magnetic and dielectric properties of NiFe2O4 nanoparticles

Nanocrystalline NiFe₂O₄ was synthesized by sol-gel route using various surfactants such as PVP, EDTA and CTAB. The effect of different surfactants on structure, magnetic and dielectric properties of the NiFe₂O₄ nanoparticles (NPs) were investigated. The prepared samples were inspected by XRD, HRSEM, and TEM. Powder XRD studies confirmed the realization of single crystalline cubic structure of the NiFe₂O₄ nanoferrites. The addition of surfactants significantly modified the crystallite size of the final products. Dielectric features of NiFe₂O₄ NPs were slightly modified with different surfactants. The magnetic results revealed an enormous decrease in coercivity and a moderate reduction in the saturation magnetization when EDTA and CTAB were used as compared to PVP. The present results declare that the adding of various surfactants in the sample preparation controls the size of NiFe₂O₄ NPs and thus noticeably influences the magnetic parameters.     

Surface Oxidized Carbon Nanotubes Uniformly Coated with Nickel Ferrite Nanoparticles

We report a facile non-templated hydrothermal synthesis method for the production of nickel ferrite (NiFe₂O₄)/carbon nanotube nanocomposite comprised of oxidized multi-walled carbon nanotube (o-MWCNT) uniformly coated with nanoparticles of NiFe₂O₄ (1–5 nm). The carboxylate groups of the o-MWCNT coordinate the nanoparticles strongly at its surface, and the size of the NiFe₂O₄ particles can be controlled by the subtle variation of reaction time and the quantity of o-MWCNT used. We believe that this method can be extended to allow the uniform coating of different spinel-type materials onto o-MWCNT and other nanocarbon materials.     

Salt-assisted solution combustion synthesis of NiFe2O4: Effect of salt type

The effects of three types of salt including NaF, KCl, and NaCl on the properties of NiFe₂O₄ nanoparticles using salt-assisted solution combustion synthesis (SSCS) have been investigated. The synthesized powders were evaluated by SEM, TEM, FTIR, XRD, and VSM analysis. Also, the specific surface area (SSA), as well as size distribution and volume of the porosities of NiFe₂O₄ powders were determined by the BET apparatus. The visual observations showed that the intensity and time of combustion synthesis of nanoparticles have been severely influenced by the type of salt. The highest crystallinity was observed in the synthesized powder using NaCl. The SSA has also been correlated completely to the type of salt. The quantities of SSA was achieved about 91.62, 64.88, and 47.22 m²g^-1 for the powders synthesized by KCl, NaCl, and NaF respectively. Although the magnetic hysteresis loops showed the soft ferromagnetic behavior of the NiFe₂O₄ nanoparticles in all conditions, KCl salt could produce the particles with the least coercivity and remanent magnetization. Based on the present study, the salt type is a key parameter in the SSCS process for the preparation of spinel ferrites. Thermodynamic evaluation also showed that the melting point and heat capacity are important parameters for the proper selection of the salt.     

Polypyrrole/NiFe2O4 composites with improved hexavalent chromium removal from aqueous solution

Polypyrrole/NiFe₂O₄ (PPy/NiFe₂O₄) composites were prepared by ultrasonic oxidative polymerization in the presence of NiFe₂O₄ nanoparticles (NPs). The nanostructure of PPy/NiFe₂O₄ was confirmed by the X‐ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM) examinations. The adsorption of Cr(VI) onto the PPy/NiFe₂O₄ composite was lowly pH dependent and the adsorption kinetics followed the Pseudo‐second‐order model. The Langmuir isothermal model well described the adsorption isotherm data and the maximum adsorption capacity increased with the increase of temperature. The maximum adsorption capacity of the PPy/NiFe₂O₄ for Cr(VI) ions was up to 50 mg/g at pH 2.0. The excellent adsorption characteristic of PPy/NiFe₂O₄ composite will render it a highly efficient and economically viable adsorbent for Cr(VI) ions removal. POLYM. COMPOS., 38:2779–2787, 2017. © 2015 Society of Plastics Engineers     

Graphene‐supported nickel ferrite: A magnetically separable photocatalyst with high activity under visible light

A straightforward strategy is designed for the fabrication of a magnetically separable NiFe₂O₄‐graphene photocatalyst with different graphene content. It is very interesting that the combination of NiFe₂O₄ nanoparticles with graphene sheets results in a dramatic conversion of the inert NiFe₂O₄ into a highly active catalyst for the degradation of methylene blue (MB) under visible light irradiation. The significant enhancement in photoactivity under visible light irradiation can be ascribed to the reduction of GO, because the photogenerated electrons of NiFe₂O₄ can transfer easily from the conduction band to the reduced GO, effectively preventing a direct recombination of electrons and holes. The results of the kinetic study indicated that the rate‐determining stage is the adsorption process of MB molecules. NiFe₂O₄ nanoparticles themselves have a strong magnetic property, which can be used for magnetic separation in a suspension system, and, therefore, the introduction of additional magnetic supports is no longer necessary. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Effect of TiN content on properties of NiFe2O4-based ceramic inert anode for aluminum electrolysis

NiFe₂O₄-based ceramic inert anodes for aluminum electrolysis doped with various TiN nanoparticles were prepared by a two-step cold-pressing sintering process to investigate how TiN affected the sintering behavior and properties of the composites. The differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray diffraction (XRD), and microstructure analysis results indicated that the Ti and N were evenly distributed in the NiFe₂O₄ matrix to form a solid solution. The maximum linear shrinkage and linear shrinkage rate were enhanced with the increase of TiN nanoparticles contents, and the sintering activation energy of initial stage was lowered from 382.63 to 279.58 kJ mol⁻¹ with the TiN nanoparticles additive range from 0 to 9 wt%. When the content of TiN nanoparticles was 7 wt%, the relative density, bending strength, and elastic modulus reached their maximum values of 97.24%, 73.88 MPa, and 3.77 GPa, respectively, whereas the minimum static corrosion rate of NiFe₂O₄-based ceramic of 0.00114 g cm⁻² h⁻¹ was obtained, mainly attributed to the relatively dense and stable microstructure. The electrical conductivity of NiFe₂O₄-based ceramics presented a clear ascending trend with increasing TiN nanoparticles content and elevated temperature, attributed to the increased concentration and migration rate of carrier.     

Preparation,characterization and electromagnetic properties of polyaniline/carbon nanotubes/nickel ferrite nanocomposites

New electromagnetic nanocomposites were prepared from polyaniline (PANI)/oxidized single‐walled carbon nanotubes (OxSWCNTs)/NiFe₂O₄ by in situ polymerization of aniline using hexanoic acid as a soft template. OxSWCNT and NiFe₂O₄ were prepared first so as to be used in the formulation of PANI composites. Transmission electron microscope (TEM) results revealed the formation of PANI nanoparticles of 60 nm diameter, OxSWCNT of 24 nm, and NiFe₂O₄ of 54 nm. Also, TEM image of the ternary composite indicated agglomerative coating of PANI appearing as a gray shells and black core of NiFe₂O₄ with widening the diameter of OxSWCNT to be around 66 nm. Dc conductivity was measured as a function of temperature. Magnetic susceptibility was measured as a function of temperature and magnetic field intensity. All samples revealed NiFe₂O₄‐dependent ferromagnetism. The activation energies for dc conductivity suggest that the conductivity is owing to hopping conduction mechanism. A synergistic effect between NiFe₂O₄ and PANI/OxSWCNT is observed. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers     

Synthesis of CoFe2O4 Nanoparticles by a Low Temperature Microwave‐Assisted Ball‐Milling Technique

Well‐crystallized Cobalt ferrite nanoparticles with mean size of 20 nm and high saturation magnetization (82.9 emu/g) were synthesized at a low temperature (≤100°C) by microwave‐assisted solid–liquid reaction ball‐milling technique without subsequent calcination. CoC₂O₄·4H₂O and Fe powder were used as raw materials and stainless steel or pure iron milling balls with diameter of 1.5 mm were used. As a contrast, solid–liquid reaction ball milling without microwave assistance was also investigated. The results showed that this is a simple, environmentally friendly, and energy‐saving technique for ferrite nanocrystal synthesis.     

Synthesis of magnetically separable core–shell structured Ni<Subscript>x</Subscript>Fe<Subscript>1−x</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>@TiO<Subscript>2</Subscript> nanoparticles photocatalysts for the degradation of organic dyes

In this paper, the core–shell structured NiFe₂O₄@TiO₂ nanoparticles and nanochains as photocatalysts were successfully prepared through hydrothermal and hydrolysis method. The as-prepared core–shell structure was composed of a magnetic NiFe₂O₄ core and photocatalytic titanium oxide coating shell. SEM and TEM images characterized the morphology of NiFe₂O₄@TiO₂ nanoparticles. Moreover, the results of XRD patterns proved that the TiO₂ coating shell consisted of anatase. The VSM measurements showed that the saturation magnetization values of NiFe₂O₄ and NiFe₂O₄@TiO₂ nanoparticles was 65 and 53 emu/g, respectively. The photocatalyst of NiFe₂O₄@TiO₂ nanoparticles exhibited the outstanding recyclable performance for RhB. And, the photo_degradation ration of maintained 69 % after the photocatalyst experienced ten photocatalysis experiments, which is better than that of Fe₃O₄@TiO₂ photocatalysts.     

Silica Functionalized Magnetic Nickel Ferrite Nanoparticles as an Efficient Recyclable Catalyst for S-Arylation in Aqueous Medium

Silica coated NiFe₂O₄ NPs has been synthesized. It has been characterized by XRD, TEM, SEM-EDX and FT-IR. The catalytic activity of the Silica coated NiFe₂O₄ NPs has been tested for the S-arylation reaction in water with high yield. In this reaction water was used as the green solvent. The effects of solvents, reaction time and catalyst amount for the reaction was reported. This catalyst showed excellent catalytic activity and recyclability. The Silica coated NiFe₂O₄ NPs catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.     

Synthesis and characterization of monodisperse NiFe2O4 nanoparticles

Narrow size distribution nickel ferrite nanoparticles with average particle size of around 6 nm has been synthesized via rapid thermo-decomposition method in the presence of oleylamine in solution which acted as neutralizing, stabilizing and reducing agent OAm coated NiFe₂O₄ NPs. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectra (FT-IR), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), Vibrating Simple Magnetometer (VSM) and also Mössbauer Spectroscopy were used for structural, morphological, spectroscopic and magnetic characterization of the product. The XRD analysis revealed the formation of single phase nickel ferrite with Fd-3m space group. Both FT-IR and TGA analyses confirmed the formation of desired nanocomposite. FT-IR analysis also showed characteristic IR absorption bands of the spinel nickel ferrite phase and oleylamine. TEM and SEM analysis showed that product have almost spherical structural morphology. TEM images showed that NiFe₂O₄ nanoparticles have narrow size distribution and Energy Dispersive X-ray (EDX) analysis confirmed the presence of metal ions in the required stoichiometric ratio. Superparamagnetic property of the product was confirmed by VSM. From ⁵⁷Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values have been determined. The Mössbauer spectra for OAm coated NiFe₂O₄ NPs. is consisting of one paramagnetic central doublets and one magnetic Zeeman sextet. Finally, the synthetic procedure can be extended to the preparation of high quality metal or alloy nanoparticles.     

Nanocrystalline/Nanosized Ni1−γFe2+γO4 Ferrite Obtained by Contamination with Fe During Milling of NiO–Fe2O3 Mixture. Structural and Magnetic Characterization

The nanocrystalline nickel ferrite (NiFe₂O₄) was synthesized by reactive milling starting from equimolar mixture of oxides. The iron contamination during milling leads to a solid state reaction between Fe and NiFe₂O₄ spinel. This reaction starts for a milling time longer than 30 h. A mixed nickel–iron ferrite (Ni_1?γFe_2+γO₄) and elemental Ni are obtained. The evolution of the nickel–iron mixed ferrite during milling and its properties were investigated using X‐ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), Laser Particles Size Analyzer and magnetic measurements. Annealing treatment (350°C/4 h in vacuum) is favorable to the reaction between phases. Replacement of Ni²⁺ cations by iron cations provided by contamination leads to the increase of lattice parameter value of the spinel structure. The magnetization of the nickel–iron mixed ferrite newly formed is larger than the nickel ferrite magnetization (13.6 μ_B/f.u. and 6.22 μ_B/f.u., respectively), due to the magnetic moment of Fe²⁺ cation which is double as compared to the Ni²⁺ cation. Magnetization of the milled samples decreases during milling due to the structural changes induced by milling in the nickel–iron mixed ferrite. The annealing induces a reordering of the cations which leads to a larger magnetization.     

Polymer–nanofiller prepared by high‐energy ball milling and high velocity cold compaction

High‐energy ball milling using comilling in a solid state by low‐temperature mechanical alloying to prepare nickel‐ferrite (NiFe₂O₄) nanopowders and ultrafine poly(methyl methacrylate) (PMMA), dispersing nanoparticles in a polymer matrix, and a uniaxial high‐velocity cold compaction process using a cylindrical, hardened steel die and a new technique with relaxation assists have been studied. The focus has been on the particle size distributions of the nanocomposite powder during the milling and on the surface morphology of the nanocomposite‐compacted materials after compaction with and without relaxation assists. Experimental results for different milling systems are presented showing the effects of milling time and material ratio. It was found that a longer mixing time give a higher degree of dispersion of the nanopowder on the PMMA particle surfaces. Furthermore, with increasing content of NiFe₂O₄ nanopowder, the reduction of the particle size was more effective. Different postcompacting profiles, i.e. different energy distributions between the upper and lower parts of the compacted powder bed, lead to different movements of the various particles and particle layers. Uniformity, homogeneity, and densification on the surfaces in the compacted powder are influenced by the postcompacting magnitude and direction. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by reducing the expansion of the compacted volume and by reducing the different opposite velocities, giving the compacted composite bed a more homogeneous opposite velocity during the decompacting stage and reducing the delay time between the successive pressure waves. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Insights into the optical,magnetic and dielectric properties of some novel polysulfone/NiFe2O4 composite materials

Novel polysulfone (PSU)/NiFe₂O₄ nanocomposites with good magneto‐dielectric properties were prepared in a simple and cost‐effective manner. Nickel ferrite nanoparticles exhibit a cubic spinel phase without any impurity phases according to X‐ray diffraction characterization. Transmission electron microscopy images of the nanoparticles showed a tetragonal particle shape with average particle size of 17–30 nm. The thermal stability of PSU proved to remain unaffected by nanoparticle concentration in the composite material. The emission spectra of the PSU/NiFe₂O₄ nanocomposites present a broad emission band located at 370 nm due to free exciton recombination. The composites exhibit hysteresis loops of a ferrimagnetic nature and good dielectric properties. Coercivity value measured at room temperature is 20.64 and 24.98 Oe and the squareness (M_r/M_s) is 0.290 and 0.225 for both polymer composite samples (4 and 24 vol% Ni ferrite). The formalism of the dielectric loss has been used to estimate the dipolar relaxations expressed by γ‐ and β‐relaxation processes. The presence of Ni ferrite nanoparticles in the PSU matrix increases the activation energy of secondary relaxations, which means a reduction of the molecular mobility in the nanocomposites as compared to PSU. © 2018 Society of Chemical Industry     

α-Arylation of oxindoles using recyclable metal oxide ferrite nanoparticles: Comparison between the catalytic activities of nickel,cobalt and copper ferrite nanoparticles

Three different spinel metal oxide catalytic systems including NiFe₂O₄, CuFe₂O₄ and CoFe₂O₄ were synthesized using co-precipitation technique and their catalytic activities were compared to each other in α-arylation of oxindole derivatives under the optimized reaction conditions. Both nickel ferrite and copper ferrite magnetic nanoparticles show approximately the same behavior in these reactions but cobalt ferrite ones indicate slightly different properties and were not as good as the other two catalysts. These superparamagnetic catalysts allowed that α-arylation of different types of oxindoles will occur in high yields under mild conditions and at very short times.     

NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> Nanoparticles Stabilized by Porous Silica Shells

Abstract  

NiFe₂O₄ nanoparticles stabilized by porous silica shells (NiFe₂O₄@SiO₂) were prepared using a one-pot synthesis and characterized for their physical and chemical stability in severe environments, representative of those encountered in industrial catalytic reactors. The SiO₂ shell is porous, allowing transport of gases to and from the metal core. The shell also stabilizes NiFe₂O₄ at the nanoparticle surface: NiFe₂O₄@SiO₂ annealed at temperatures through 973 K displays evidence of surface Ni, as verified by H₂ TPD analyses. At 1,173 K, hematite forms at the surface of the metallic cores of the NiFe₂O₄@SiO₂ nanoparticles and surface Ni is no longer observed. Without the silica shell, however, even mild reduction (at 773 K) can draw Fe to the surface and eliminate surface Ni sites.     

Effect of Cobalt and Nickel Doping on Structural and Magnetic Properties of Iron Oxide Nanoparticles

Two series samples of Iron Oxide nanoparticles doped with nickel and cobalt with different doping values (x?=?0.01; 0.03; 0.05 and 0.07), were successfully synthesized by using sol–gel method, and then they were characterized by X-ray diffraction, scanning electron and vibrating sample magnetometer (VSM). X-ray diffraction analysis of two series samples showed the formation α-Fe₂O₃ nanoparticles, accompanied by two phases iron spinels, CoFe₂O₄ and NiFe₂O₄. In addition, the variations in grain size were observed for both two series. The observation by scanning electron microscopy reveals a change in the morphology of the grains of all the samples doped, which confirm the cobalt and nickel effect on the morphology of iron oxide nanoparticles. Magnetic measurements which were measured by VSM showed significant magnetic parameters such as coercivity and magnetization besides the ferromagnetic behavior of both two series doped with Cobalt and Nickel.

     

Synthesis and rheological characterization of nano-magnetorheological fluid using inverse spinel ferrite (NiFe2O4)

In recent years, the utilization of nanoparticles for nano-magnetorheological fluid (NMRF) synthesis is gaining popularity in automotive applications. From this perspective, the nickel ferrite (NiFe₂O₄) nanoparticles were prepared by gel burning method and characterized using the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy-energy dispersive X-ray analysis (FESEM-EDX), and vibration sample magnetometer (VSM). The XRD and FTIR results showed the phase formation and characteristic metal–oxygen M–O vibrations. The FESEM images showed quasi-spherical crystallites with considerable agglomeration. The magnetic properties measured showed the ferromagnetic nature of NiFe₂O₄. The nanosized NiFe₂O₄ was used for NMRF preparation and characterization.