Magnetic Ni Nanoparticles Research Articles

Magneto-Sensitive Ni/C Adsorbents: Synthesis, Properties and Applications

A series of microporous carbons (chars) containing various amounts of magnetic Ni nanoparticles were prepared using a simple procedure. The resorcinol–formaldehyde polymers containing nickel(II) acetate was carbonized to produce chars (labelled as Ni/C-20, Ni/C-35 and Ni/C-50). All chars were characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption and scanning electron microscopy methods. The formation of Ni crystallites (18 nm in size) occurs in carbon spheres measuring 1–2 μm in diameter. The Raman spectra show that the content of Ni influences the carbon structure. Dye-separation performance by Ni/C was investigated using methylene blue. The adsorption capacity was 26.6, 20.8 and 15.1 mg/g for Ni/C-20, Ni/C-35 and Ni/C-50, respectively.

Room-Temperature Synthesis of Ni Nanoparticles as the Absorbent Used for Sewage Treatment

The magnetic Ni nanoparticles of 10–30 nm in size were synthesized by the reduction of Ni2+by NaBH4at room temperature. The amount of added water in the formation of Ni nanoparticles is a significant factor, which ensures that Ni nanoparticles are not oxidized by oxygen. XRD patterns and FESEM micrographs showed the constituent and structure and micromorphology. Congo red was used as adsorbate to quantitatively examine the adsorption capability of Ni nanoparticles for the organic dyes in industry wastewater. The magnetic hysteresis measurement indicated that the Ni nanoparticles presented ferromagnetic properties. The experimental results showed the as-obtained Ni nanoparticles might be a potential adsorbent in sewage treatment process.

Anchoring superparamagnetic core–shells onto reduced graphene oxide: fabrication of Ni–carbon–rGO nanocomposite for effective adsorption and separation

The magnetic Ni nanoparticles encapsulated in carbon shells were anchored on to reduced graphene oxide. The excellent removal ability of organic dyes and enhanced separation efficiency make NGC a useful candidate for waste water treatment.

One-step preparation of hydrophilic carbon nanofiber containing magnetic Ni nanoparticles materials and their application in drug delivery

A one-step process for the synthesis of hydrophilic carbon nanofibers (CNFs) through CO2 hydrogenation on NiNa/Al2O3 was developed for the loading and targeted delivery of the anticancer drug doxorubicin (DOX). CNFs that were synthesized on NiNa/Al2O3 for 9h at 500°C exhibited an adequate magnetic response and a large content of hydrophilic oxygen-containing functional groups on the carbon surface, resulting in excellent colloidal solution. The CNF material exhibited a highly efficient capacity for DOX adsorption, particularly at pH 9.0. The loading and release of DOX was strongly pH dependent, possibly due to electrostatic and π–π stacking interactions between DOX and CNF sample. The Langmuir isotherm and pseudo second-order kinetics of DOX-loaded CNFs were well-modeled for the process of DOX adsorption. DOX-loaded CNF targeted cancer cells more selectively and effectively than free DOX and exhibited a marked tendency to kill HeLa cancer cells and reduced toxicity to normal human primary fibroblast (HPF) cells.

Experimental investigations in heat transfer and friction factor of magnetic Ni nanofluid flowing in a tube

A magnetic nanofluid was prepared by dispersing magnetic Ni nanoparticles in distilled water. The nanoparticles were synthesized by chemical co-precipitation method and characterised by X-ray diffraction and atomic force microscopy. The average particle size was measured by the dynamic light scattering method. Thermal conductivity and absolute viscosity of the nanofluid were experimentally determined as a function of particle concentration and temperature. In addition, the Nusselt number and friction factor were experimentally estimated as a function of particle concentration and Reynolds number for constant heat flux condition in forced convection apparatus with no phase change of the nanofluid flowing in a tube. The experiments were conducted for a Reynolds number range of 3000–22,000, and for a particle concentration range from 0% to 0.6%. The results indicate that both Nusselt number and friction factor of the nanofluid increase with increasing particle volume concentration and Reynolds number. For 0.6% volume concentration, the enhancement of Nusselt number and friction factor is 39.18% and 19.12%, respectively, as compared to distilled water under the same flow conditions. It was verified the classical Gnielinski and Notter–Rouse correlations under predict the Nusselt number of the nanofluid; therefore, new generalized correlations are proposed for the estimation of the Nusselt number and friction factor based on the experimental data.

Inverse magnetic proximity effects in superconducting In-Ni and Sn-Ni nanoparticle assemblies

We report on experimental evidence of non-s-wave pairing in In and Sn nanoparticle assemblies. The superconducting transition temperature TC of the In and Sn nanoparticles varies noticeably with the particle diameter. Surprisingly, TC shifts to a noticeably higher temperature when magnetic Ni nanoparticles are introduced into the vicinity of the superconducting nanoparticles. The TC increases further when the magnetic Ni nanoparticles are brought even closer to the superconducting nanoparticles. There is a critical Ni composition and a critical spatial separation between the magnetic and superconducting nanoparticles that must be reached before their magnetic proximity will suppress the superconductivity. A qualitative mechanism is proposed to understand the present observations.

Enhanced Superconducting Parameters of Zero-Dimensional Sn Nanoparticles by Magnetic Proximities

We report on the results of ac magnetic susceptibility measurements made on Sn and Sn–Ni nanoparticle assemblies. The thermal profiles of the magnetic susceptibility of the nanoparticle assemblies can be described by Scalapino’s expression. Inverse magnetic proximity effect is observed, as the T C of the superconducting Sn nanoparticles is found to be noticeably increased, when magnetic Ni nanoparticles are introduced into the vicinity of the superconducting Sn nanoparticles. Closing up the spatial separations between Sn and Ni nanoparticles leads to a further increase in T C.

In situ modification of Fe and Ni magnetic nanopowders produced by the electrical explosion of wire

Iron and nickel spherical magnetic nanoparticles (MNPs) with mean diameter 50–80 nm were prepared by the electric explosion of wire. The advantage of this method is that it provides a very high production rate up to 200 g/h and requires low energy consumption of 25 kW h/kg. The as-prepared MNPs were modified in situ in hexane, toluene, chloroform, and the solutions of polystyrene in toluene, in an inert atmosphere at room temperature in order to provide both the stability at ambient conditions and tunable surface properties. Hexane was an inert liquid for Fe and Ni MNPs. In the case of toluene the surface of as-prepared Fe or Ni MNPs acted as a catalyst for the condensation reaction of aromatic organic compounds forming irregular polycyclic structures. The treatment with toluene led to the deposition of carbon and formation of “hair-like” ordered structures on the surface of the MNPs. Chloroform chemically interacted with Fe MNPs, forming FeCl2. The treatment of MNPs with the solution of polystyrene in toluene resulted in the adsorption of polymer and the formation of 3–6 nm polymeric coatings on the surface. The obtained magnetic properties (like the magnetization value for Ni MNPs up to 52 emu/g and Fe MNPs up to 179 emu/g) at room temperature make these MNPs competitive candidates for nanocomposites for microwave and other technological applications.

Facile synthesis of a Ni(ii)-immobilized core-shell magnetic nanocomposite as an efficient affinity adsorbent for the depletion of abundant proteins from bovine blood.

In this study, a facile and efficient separation of abundant proteins from bovine blood using core-shell structure nanoparticles with a magnetic core and an immobilized metal affinity ligand iminodiacetic acid (IDA) chelating Ni(ii) is presented. Firstly, Fe3O4 magnetic nanoparticles (MNPs) were synthesized through a solvothermal method and then were conveniently surface-modified with 3-(methacryloyloxy) propyltrimethoxylsilane as anchor molecules to donate vinyl groups. Next a high density poly(4-vinylbenzylchloride) (PVBC) shell was synthesized on the surface of silica-coated Fe3O4 MNPs via distillation-precipitation polymerization. After the PVBC shell reacted with iminodiacetic acid (IDA) in alkaline aqueous solution, the magnetite was charged with Ni2+ to form Ni(ii)-IDA functionalized hybrid Fe3O4@PVBC@IDA-Ni MNPs. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and a vibrating sample magnetometer (VSM) were employed to evaluate the size, morphology and magnetic property of the resulting magnetic nanospheres. The high saturation magnetization (48.1 emu g-1) provides the materials with the convenience of magnetic separation under an external magnetic field and they can be subsequently reused. The core-shell Fe3O4@PVBC@IDA-Ni MNPs exhibit excellent performance in the separation of protein bovine hemoglobin (BHb), and the binding capacity is as high as 1988 mg g-1. In addition, the Fe3O4@PVBC@IDA-Ni MNPs can be used in selective removal of abundant protein Hb in the bovine blood samples. This opens a novel route for its future application in removing abundant protein in proteomic analysis.

Sputtering deposition of magnetic Ni nanoparticles directly onto an enzyme surface: a novel method to obtain a magnetic biocatalyst

A simple one-step method based on the sputtering deposition of Ni nanoparticles (NP) has been developed for the production of magnetic biocatalysts, avoiding the complications and drawbacks of methods based on chemical functionalisation or coating of magnetic NP. This new technique provided high levels of recovery, reusability and catalytic activity for the lipase-Ni biocatalyst.

Pulsed Plasma Synthesis of Iron and Nickel Nanoparticles Coated by Carbon for Medical Applications

Fe and Ni magnetic nanoparticles coated by carbon were synthesized between the Fe–Fe and Ni–Ni metal electrodes, submerged in ethanol using pulsed plasma in a liquid method. Iron coated carbon (Fe@C) nanoparticles have an average size of 32 nm, and Ni@C nanoparticles are 40 nm. Obtained samples exhibit a well-defined crystalline structure of the inner Fe and Ni cores, encapsulated in the graphitic carbon coatings. Cytotoxicity studies performed on the MCF-7 (breast cancer) cell line showed small toxicity about 88–74% at 50 µg/mL of Fe@C and Ni@C nanoparticles, which can be significant criteria for use them in medical cancer treatment. In addition, appropriate sizes, good magnetic properties and well-organized graphitic carbon coatings are highlight merits of Fe@C and Ni@C nanoparticles synthesized by pulsed plasma.

Fabrication of magnetic Ni nanoparticles functionalized water-soluble graphene sheets nanocomposites as sorbent for aromatic compounds removal

The magnetic Ni nanoparticles functionalized water-soluble graphene sheets nanocomposites (Ni@GSs-C(CH3)2COONa) were fabricated via a facile and mild strategy. We designed a simple and efficient approach (the addition of cyano radicals) to improve the water solubility of nanocomposites. The Ni@GSs-C(CH3)2COONa nanocomposites had great potential as an effective absorbent for removing aromatic compounds from waste water owing to their rapid absorption rate, high absorption capacity, convenient magnetic separation and re-use property.

Fabrication and characterisation of multiwalled carbon nanotubes decorated by magnetic Ni nanoparticles

Magnetic carbon nanotube (CNT) composites have been successfully fabricated by employing a microwave assisted method after sensitisation and activation. The phase structures and morphologies of the composites were characterised in detail by transmission electron microscope and X-ray powder diffraction. The results show that sensitisation and activation are absolutely necessary for a dense layer of magnetic nanoparticles obtained on the surface of CNTs. Magnetic measurements using a vibrating sample magnetometer demonstrate that the prepared composites are ferromagnetic.

One-step preparation of carbon nanotubes with nickel as the core

CNTs with core-shell structure were successfully synthesized by a microwave-assisted polyol method, and magnetic Ni nanoparticles were employed as a catalyst. The preparation method is fast and simple. The structures, morphology and magnetic properties of the as-synthesized samples were investigated using Raman spectrometer, X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), respectively. The XRD results suggested that Ni particles used as a catalyst in our experiment were nano-sized. In this paper, magnetic Ni nanoparticles were employed as a catalyst, and an electric spark on metal Ni nanoparticles with the microwave eddy current effect could induce CNTs’ formation with the further reaction. The length of hollow carbon nanotubes was micro-sized and the diameters of most of the CNTs were varying from 18 to 20 nm according to the TEM images. Magnetic measurements demonstrated that CNTs with core-shell structure indicated a characteristic ferromagnetic behavior compared with Ni nanoparticles.

Chemical Synthesis and Characterization of Nickel Powder

The synthesis of magnetic Ni nanoparticles is being investigated by the reduction of NiO nanoparticles in the presence of hydrogen gas. In this study, nanocrystalline NiO particles have been synthesized by a homogenous carbonate precipitation method employing nickel electrolyte (NiSO4) as the source of nickel and ammonium hydrogen carbonate as the precipitating agent. Nickel electrolyte (NiSO4) was obtained after processing of sea nodules by the roasting-ammonia leaching-solvent extraction method. The physicochemical characterization of NiO and Ni particles, i.e., bright field image by transmission electron microscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray analysis, Fourier transform-infrared (FT-IR) study, and magnetic measurements by vibration sample magnetometer (VSM) are studied. The particles are observed to be superparamagnetic.

One-step synthesis of carbon nanotubes with Ni nanoparticles as a catalyst by the microwave-assisted polyol method

Carbon nanotubes (CNTs) were firstly synthesized by the microwave-assisted polyol method and magnetic Ni nanoparticles were employed as a catalyst in the process. The structures, morphologies and magnetic properties of the as-synthesized samples were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. Our results indicated that CNTs can be synthesized after the observation of a small electric spark with Ni particles used as a catalyst. TEM showed that the length of the hollow carbon nanotubes was of the order of micron. VSM demonstrated that Ni/CNTs composite was ferromagnetic characteristic with hysteretic behavior at room temperature.

Development of a Novel and Bi-Functional Quantum Dots as FRET Energy Donor

A novel CdTe/Ni QDs which combined both magnetism and fluorescence was successfully synthesized and its optical properties were investigated. Ni magnetic nanoparticles (MNPs) were synthesized and used as magnetic core, CdTe quantum dots (QDs) were applied as fluorescent shell material, the qualified magnetic CdTe/Ni quantum dots (mQDs) were achieved via layer-by-layer process using 1,6-hexylenediamime as linker, surface charge types of MNPs and mQDs were confirmed with a delsa nano beckman coulter. Morphology of the prepared Ni MNPs and CdTe/Ni mQDs was characterized by transmission electron microscopy (TEM), and optical properties were investigated with fluorescence spectrum (FS). Qualified CdTe/Ni mQDs with high fluorescence and narrow maximum emission peak width were obtained under the optimum conditions. Surface zeta-potential of CdTe QDs and Ni MNPs were estimated to be -36.2 and 27.97mV, respectively. TEM data indicated that ca 20nm of Ni MNPs and ca 25nm of CdTe/Ni mQDs were prepared, respectively; the size-increasing indicated the formation of CdTe shell on the Ni MNPs core. Narrow half peak width of emission peak was detected and calculated to be about 50nm via FS. High fluorescence intensity of CdTe/Ni mQDs was determined and brilliant yellow solution was observed when excited under UV360nm. The synthesized CdTe/Ni mQDs showed excellent magnetic property, and can be magnetically concentrated with a common magnet. The obtained data indicated that the prepared bi-functional CdTe/Ni mQDs possess excellent magnetic and fluorescent properties, and it can be used as a energy donor in DNA sensing based on fluorescence resonance energy transfer (FRET).

Magnetic alignment of Ni-coated single wall carbon nanotubes in heat transfer nanofluids

Thermal conductivity (TC) of heat transfer nanofluids containing magnetic-metal-coated carbon nanotubes can be significantly enhanced (>60%) by applied magnetic field. In this paper, we report the observed real images of Ni-coated single wall carbon nanotubes in water and oils (polyalphaolefin, polyol ester) under magnetic field by high speed microscopy, and correlate them with TC measurements. Initially, the nanotubes are randomly dispersed in the fluid, however, on longer holding in magnetic field the nanotubes gradually stretch and are finally aligned. The chain length in the images is found to be around 30∼150 μm, which is much longer than the real length of individual nanotubes (5∼40 μm), indicating that nanotubes are aligned and form some chains and clusters. Because of the semicontinuous nature of Ni magnetic nanoparticles, as well as the viscosity resistance of the fluid itself, it takes some time for the Ni-coated nanotubes to respond to the applied magnetic field and align. Time dependent TC experiments indicate that alignment process dominates the TC enhancement rather than microconvection. Finally, scanning electron microscopy images also show that the Ni coated nanotubes are aligned well under the influence of a magnetic field. Transmission electron microscopy images indicate that nickel remains stable and attached onto the nanotubes after the magnetic field exposure and movements.

Chemical synthesis of monodisperse γ-Fe–Ni magnetic nanoparticles with tunable Curie temperatures for self-regulated hyperthermia

Magnetic nanoparticles (MNPs) possessing low Curie temperatures (TC’s) offer the possibility for self-regulated heating of cancer cells, where the TC acts as an upper limit to heating to prevent damage to neighboring healthy tissue. We report the synthesis of monodisperse metastable fcc γ-phase Fe–Ni MNPs possessing tunable TC’s, whose stoichiometries have been predicted from metastable extensions to an equilibrium Fe–Ni phase diagram. Metastable alloys have been predicted within the constructs of the T0 construction in the Fe–Ni eutectoid phase diagram. Fe–Ni MNPs have been synthesized via chemical reduction in Fe- and Ni-precursors with stoichiometries ranging from Fe90Ni10 to Fe70Ni30. Mn-precursors have been added to further reduce the alloy’s TC. MNP morphology and structure have been confirmed by x-ray diffraction and transmission electron microscopy while magnetic properties were investigated using vibrating sample magnetometry. Fe70Ni30 MNPs were found to have a TC of 82 °C and specific magnetization of 66 emu/g. Addition of 1 wt % Mn to Fe75Ni25 reduced the TC to 78 °C, which is the lowest reported for fcc Fe–Ni alloys. We also report a model for radio frequency self-regulated heating, in which the maximum achievable temperature of water-MNP suspensions (TC<100 °C) or octyl ether-MNP suspensions (TC>100 °C) is approximately the TC of the MNPs suspended in the solution.

Thermodynamic Phase Formation of Morphology and Size Controlled Ni Nanochains by Temperature and Magnetic Field

A series of highly uniform one-dimensional Ni nanochains, with diameters ranging from 20 to 200 nm, have been synthesized by a facile, template-free, wet chemical method at diverse temperature and magnetic field. Our results indicate that the crystallite size, diameter and length of the prepared nanochains depend critically on the reaction temperature. The characteristic thermodynamic cohesive energies, ΔED and ΔEL, are obtained for the formation of the Ni nanochains. In addition, the chain length also depends on the applied field because of the Zeeman energy of the magnetic Ni nanoparticles. For the morphology control, an external field is required in order to obtain axially aligned rather than dendritic nanochains. The size-dependent magnetic properties are studied systematically. The saturation magnetization is shown to reduce inversely with the chain diameter, attributable to a core−shell structure. The thickness of the shell which encloses the ferromagnetic Ni core is determined to be about 2.3−3.4 nm.