Vibrating Sample Magnetometer Studies Research Articles

Synthesis of nickel-cobalt ferrite/graphene oxide nanocomposites

Current investigation is an attempt to study the structural, optical, magnetic and dielectric properties of Ni0.5Co0.5Fe2O4/graphene oxide (NCF/GO) nanocomposites. NCF/GO nanocomposites were synthesized through the ultrasonication technique. NCF nanoparticles (NPs) and GO (with varying weight percentages of GO) were synthesized through sol–gel auto-combustion and modified Hummer’s method, respectively. The effect of nickel–cobalt ferrite NPs incorporation on graphene oxide was studied using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and Impedance Analyzer. electrical and dielectric measurements. XRD and FTIR studies showed and confirmed the formation of both spinel for the NCF NPs and amorphous graphene oxide for NCF/GO nanocomposites. The crystallite size and lattice parameter for NCF NPs were found in the range of 21–47 nm and 8.33–8.36 Å, respectively. The optical band gap was found in the range of 1.73–1.83 eV with increasing GO concentration. VSM studies revealed that the saturation magnetization (Ms) value for NCF/GO nanocomposites is found to be decreased from 59 emu/g (for NCF) to 30 emu/g (for 60 wt% of GO) with increased GO weight percentage. There was a drastic variation observed in the value of coercivity (Hc) for NCF and NCF/GO nanocomposites. However, it remains almost constant within NCF/GO nanocomposites. Dielectric studies showed the exponentially decaying nature of dielectric constant and loss tangent with logarithmic frequency. Further, the dielectric constant is increased with increasing GO content. A maximum dielectric constant is observed for NCF/GO nanocomposites with 60 wt% of GO. The AC conductivity is found to be increasing with an increase in GO weight percentage and showed its sharply increasing nature at higher frequencies.

Optical, conductivity, dielectric, and magnetic properties of polymer nanocomposite based on PAM/cs matrix and ZnFe2O4 NPs for use in magneto-electronic and energy storage capacitor devices

In this study, a cast synthesis approach was used to create flexible nanocomposite films made of polyacrylamide (PAM), chitosan (Cs), and zinc ferrite nanoparticles (ZnFe2O4 NPs). XRD analysis was used to examine the composite structure. They demonstrated the effective interaction between ZnFe2O4 NPs and PAM/Cs blend. As the concentration of nanomaterial in the host polymer matrix grew, it was observed that the PAM/Cs matrix's direct and indirect energy band gaps decreased while its absorbance of ultraviolet–visible radiations increased. The nanocomposite's AC conductivity was significantly higher than that of the blend, and 2.5 wt percent of the nanocomposite showed the highest electrical conductivity. It was observed that as frequency raised, the ε′ and ε″ declined though the concentration of nanoparticles enhanced these characteristics. Because of the high dielectric permittivity of ZnFe2O4, the values of ε′ and ε″ raised as ZnFe2O4 were higher. The outcome of the vibrating sample magnetometer (VSM) demonstrated the ferromagnetic property of the produced nanocomposites. Furthermore, the VSM study shows that as the nanoparticles content increases, the PAM/Cs/ZnFe2O4 nanocomposites' Ms, Hc, and Mr also increase. These PAM/Cs/ZnFe2O4 films were shown by the experimental results to be promising candidates for bandgap-regulated materials, electromagnetic interference shielders, frequency tunable nanodielectric, and flexible dielectric substrates for future microelectronic, optoelectronic technologies, and capacitive energy storage.

Structural and magnetic properties of Fe and Ni co-doped SnO2 nanoparticles prepared by co-precipitation method

In this research work Fe and Ni co-doped Tin oxide (SnO2) nanoparticles have been prepared by co-precipitation method. The samples were prepared at various combination of Fe and Ni from 0% up to 10%. The produced nanoparticles were studied by x-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–vis Spectrophotometer, Fourier Transformation Infrared Spectroscopy (FTIR) and Vibrating Sample Magnetometer (VSM). The XRD study reveals the formation of rutile structure of the undoped and doped SnO2 nanoparticles with the average crystallite size of 1.5–10.8 nm. Metal oxide bonding is confirmed through FTIR measurement. Optical band gap redshift (3.9 to 3.64 eV) with doping of Fe and Ni atom is observed. SEM image confirms the formation of spheroidal nanoparticles and size of the nanoparticle varies from 36 to 15 nm. The VSM study shows the ferromagnetic phase transition at 7% Ni, Fe doped SnO2 nanoparticles. This ferromagnetism arises for the oxygen vacancies and defect states. Further, increase of doping concentration of 10%, nanoparticles show the phase transition from ferromagnetic to paramagnetic. Such transition can be applicable in hyperthermia treatment and memory devices.

Bioinspired ferromagnetic CoFe2O4 nanoparticles: Potential pharmaceutical and medical applications

Abstract The primary goal of this work was to develop a cost-effective, non-toxic, eco-friendly, and simple approach for the green synthesis of CoFe2O4 nanoparticles (NPs) using Aloe vera leaf extract by the sol–gel auto-combustion method. In order to figure out their structural, morphological, and magnetic properties, the synthesized NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), dynamic light scattering (DLS), zeta potential, and vibrating-sample magnetometer (VSM). XRD analysis showed that particles had a single-phase spinel crystalline structure with an average crystalline size of 33.5 nm. Under VSM studies, the produced NPs exhibit a soft ferromagnetic property. SEM revealed that the as-prepared NPs were agglomerated due to their magnetic behavior. To the best of our knowledge, the anticandidal, antibiofilm, antibacterial, and anticancer activities of CoFe2O4 NPs toward drug-resistant gram-positive and gram-negative bacteria, as well as fungal strains, have been comprehensively investigated for the first time. The synthesized NPs had a minimal inhibitory concentration of 0.25–0.75 mg/ml against the tested pathogens. CoFe2O4 NPs inhibited the biofilm formation by 37.3–61.8% in selected strains at concentrations of 0.125–0.5 mg/ml. It was observed that the NPs not only suppress biofilm formation but also eradicate established mature biofilms by 50.9–64.49% that was further supported by SEM. SEM analysis shows that NPs significantly inhibit the colonization and aggregation of tested biofilm strains. Light microscopic analysis revealed that NPs completely inhibit the development of hyphae and filaments in Candida albicans, which significantly attenuates their pathogenicity. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and 4′,6-diamidino-2-phenylindole (DAPI) staining demonstrate that NPs significantly inhibit the proliferation of HCT-116 and HeLa cells. Furthermore, the SEM images of treated cells showed wrinkled and damaged cell walls, indicating the disruption and disorganization of the membrane. This study showed that the synthesized NPs were effective in inhibiting the growth of drug-resistant bacteria, candida, and their preformed biofilms as well. Thus, these NPs with broad-spectrum applications could be exploited in medical settings to diminish biofilm-based infections caused by these pathogenic strains.

Biosynthesis of a tri‐metallic nanoalloy for magnetic and biomedical applications

The tri‐metallic magnetic nanoalloy synthesized via the eco‐friendly procedure discussed here contains cobalt (Co), nickel (Ni), and zirconium (Zr) metals in a 3:1:1 M ratio (Co3O4.NiO.ZrO2 nanoalloy). Two different plant extracts which are rich in biologically active compounds from Spermacoce hispida and Vernonia cinereum were combined to get a multispecies nanoalloy with magnetic properties and medicinal values. The Fourier transform infrared, X‐ray diffraction, and transmission and scanning electron microscopes analyses confirmed the spherical shape of the bioinspired Co3O4.NiO.ZrO2 nanoalloy. The average size of our nanoalloy was 32 nm, but the individual nanoparticles are between 21 and 73 nm in size. A vibrating sample magnetometer study of the magnetic characteristics of the nanoalloy reveals strong saturation magnetization (12.42 emu/g), low retentivity (Mr), and low coercivity (Hc) (282.36 Oe). The higher saturation magnetization in nanoalloy is attributed to their larger particle size, a high degree of crystalline structure, and slight external spinning deformation. The low coercive field (Hc) value reveals the unique soft nature of our nanoalloy. The disc diffusion study confirms that a 6.3 μg/mL solution of the nanoalloy kills almost 96% of the harmful bacteria like Bacillus subtilis (29 mm), Bacillus cereus (26 mm), and Escherichia coli (21 mm). It shows a moderate effect of 85% killing factor against Staphylococcus albus (17 mm), Pseudomonas aeruginosa (13 mm), and Klebsiella pneumoniae (15 mm) bacteria.

Electron spin resonance and induction heating studies of zinc substituted (Mn, Co) ferrite nanoparticles for potential magnetic hyperthermia applications

This study presents an investigation on the various spin relaxation processes taking place at X-Band microwave energy in Zn substituted MnFe2O4 and CoFe2O4 and their induction heating studies. The material properties of these citric acid assisted sol-gel synthesized nanoparticles have been explored using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscope, Vibrating sample magnetometer (VSM) and Electron spin resonance spectroscopy. XRD and Rietveld refinement confirm the face centered cubic spinel structure of the synthesized samples, which is further supported by the observation of absorption bands characteristic of the spinel ferrites in the FTIR spectra. The remanence, coercivity and effective magnetocrystalline anisotropy values from VSM studies show lower value with zinc substitution which is desirable for biomedical application. Various spin resonance parameters like gyromagnetic ratio, peak to peak linewidth, resonance field, spin-lattice and spin-spin relaxation times have been calculated. The induction heating studies of the samples in an alternating magnetic field have been carried out using a field strength of 4.58 × 109 Am-1s-1. All the investigated MNPs are able to raise the temperature to the therapeutic limit of 42–45 °C. The specific absorption rate (SAR) which describe the heating potential of the MNPs is calculated using four different concentrations of each sample - 5 mg mL-1, 10 mg mL-1, 15 mg mL-1 and 20 mg mL-1. SAR values are found to decrease with increase in concentration and achieve the highest value of 303 W/g for Co0.5Zn0.5Fe2O4 nanoparticles with 5 mg mL-1 concentration. The ability of the MNPs to give rise to the therapeutic temperature points toward their suitability as an effective heat mediator in magnetic hyperthermia treatment of cancer.

Effects of calcination temperatures on structural, functional, morphological, and magnetic properties of strontium ferrite (SrFe2O4) nanoparticles

In this proposed work, the strontium ferrite (SrFe2O4) nanoparticles were successfully synthesized in the presence of strontium nitrate (Sr (NO3)2) and ferric nitrate (Fe (NO3).9H2O) as primary sources by using chemical co-precipitation method. The prepared powders were kept different calcinations temperature (650, 750 and 850 ​°C) and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) techniques. The XRD patterns demonstrated the cubic and orthorhombic phase of spinel formation and FTIR transmittance spectra confirmed the presence of strontium ferrite related molecular functional groups. Further, SEM micrograph showed spherical nanoparticles with less agglomerated structure. VSM studies revealed the hard magnetic properties with the highest saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) of 22.17 emu/g, 11.807 emu/g and 5662.6 ​Oe respectively by VSM.

Green-synthesized Nickel oxide nanoparticles: Magnetic and biomedical applications

In this work, cubic Nickel oxide (NiO) nanoparticles (NPs) were prepared by a hotplate combustion process using Calotropis gigantea (crown flower) leaf extract as fuel. The synthesized NPs were characterized by analytical techniques like Powder X-ray diffraction (PXRD), UV–visible spectroscopy (UV–vis), Transmission electron microscope (TEM), Scanning electron microscope (SEM), and Vibrating sample magnetometer (VSM). PXRD results confirmed the formation of single-phase crystalline NiO NPs with an average crystallite size of 17.06 nm. Further, SEM and TEM analysis shows the formation of hexagonal-shaped NiO NPs with agglomeration. The energy bandgap of 3.04 eV was observed for the NiO NPs by optical studies. The vibrational stretching mode of Ni-O (431 cm−1) was validated by FTIR analysis. VSM studies reveal room temperature ferromagnetic property. The as-prepared NPs were subjected to a cytotoxicity test against liver cancer (HepG2) cell line using an MTT assay and significant anticancer activity was observed. Furthermore, an antibacterial assay indicates gram-negative bacteria is more defiant of antibiotic drugs than gram-positive bacteria.

Tuning the Optical Properties of ZnO by Co and Gd Doping for Water Pollutant Elimination

In the present study, pure, Co, Gd, and Co/Gd di-doped ZnO nanoparticles were synthesized via the co-precipitation synthesis route. The prepared samples were characterized through different techniques such as the X-ray diffraction method (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, photoluminescence (PL)spectroscopy, and an impedance analyzer and vibrating sample magnetometer (VSM). The XRD pattern shows ZnO’s wurtzite hexagonal crystal structure; moreover, the shifting of characteristic peaks toward the lower angle indicates the inclusion of Co and Co/Gd in the ZnO host lattice. SEM micrographs show various morphologies such as rods, the agglomeration of particles, and spherical nanoparticles. The UV-Vis spectroscopy reveals that the absorption increased in the visible region and there was a substantial redshift for the doped samples. The bandgap decreased from 3.34 to 3.18 eV for the doped samples. The PL spectra show near-edge and inter-band transitions; the origin of inter-band transitions is attributed to the defect states present within the bands. The dielectric constant is strongly frequency dependent and decreases with Co and Co/Gd doping, while the electrical conductivity increases. A VSM study indicates that pure ZnO is diamagnetic, while the Co and Co/Gd doped ZnO nanoparticles showed ferromagnetic behavior. Under UV-visible light irradiation, the Co/Gd-ZnO nanoparticles showed higher photocatalytic activity than the ZnO nanoparticles. The enhanced photocatalytic activity may be attributed to a decreased bandgap with doping.

Synthesis, Structural and Antibacterial Activity of Zn1-xNixFe2O4 Nanoparticles

In present work, nickel doped zinc ferrite nanoparticles were prepared via hydrothermal technique. The prepared nanopowders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectroscope (FTIR), vibrating sample magnetometer (VSM) and antimicrobial activity. The XRD analysis revealed that the presence of sharp diffraction peaks and cubic-structure of the prepared samples. SEM analysis revealed that there is a significant degree of agglomeration in the samples, whereas VSM studies revealed the magnetic behaviour and cation distribution in the prepared samples. The prepared nanopowder has also been evaluated for its antimicrobial properties against Gram-negative bacteria (Enterobacter aerogenes) and Gram-positive bacteria (Enterococcus faecalis). An increasing in the ratio of nickel to zinc in ferrite nanoparticles led to an evident rise in their activity. These nanoparticles with enhanced structure and antimicrobial properties could find applications in hygiene, therapeutic and textile fields.

Synthesis and Characterization of some metals (Sn, Ni, Zn and Co) doped with CdO Nanoparticles by Co-Precipitation method for super capacitor applications

In this present investigation, a set of pure and some metals doped Cadmium oxide nanoparticles were synthesized by the way of co-precipitation method. The precursor materials used in this current work were cadmium nitrate, tin (II) chloride, nickel acetate, zinc acetate dihydrate and cobalt (II) chloride has been make uses of a precursor materials. The as-synthesized nanopowders were characterized by XRD, FTIR, UV-Vis and SEM analysis. The X-Ray Diffraction patterns revealed a polycrystalline having the characteristic peaks are well matched with the phase purity of cubic structure. Scanning Electron Microscope exhibit surface morphology, Fourier Transform Infrared spectrum has affirmed the presence of the functional groups present in the pure and metals doped cadmium oxide nanoparticles. The room temperature photoluminescence (PL) and Ultra Violet-Vis near Infra measurement studies were carried out to optical properties and band gap of the materials. The band gaps of the materials were observed to be 2.47 eV for pure CdO, 2.32 eV for metals doped CdO which were appraise from Tauc’s plot. The average particle diameter of CdO nanoparticles was measured in the nanometer range using a dynamic light scattering (DLS) particle size analyzer. The magnetic properties to express vibrating sample magnetometer studies (VSM). The uppermost electrochemical capacitance implementation is using Cyclic Voltammetry analysis, which indicates capable electrode materials for electrochemical super capacitor applications.

Room-Temperature Ferromagnetism in Cu/Co Co-Doped ZnO Nanoparticles Prepared by the Co-Precipitation Method: For Spintronics Applications

In current work, pure ZnO and Zn0.96–xCu0.04CoxO (0 ≤ x ≤ 0.05) nanoparticles were synthesized by the co-precipitation method. Structural analysis and phase determination of the formed nanoparticles was carried out using X-ray diffraction (XRD) and Williamson–Hall plots. The hexagonal wurtzite structure was manifested by all the samples with divergent microstructures. The change in lattice parameters, bond length, dislocation density, and lattice strain indicates that Cu and Co were successfully incorporated. Average crystallite size was found to be in the range of 32.16–45.42 nm for various doping concentrations. Field emission scanning electron microscopy results exhibited that the surface morphology is an amalgam of spherical-like and hexagon-like structures. Spherical-shaped grains were homogeneous and evenly distributed all over the structure. Fourier transform infrared spectra indicated that the absorption bands were blue-shifted with increasing Co concentration. The UV–visible absorption spectra showed high absorption in the UV region and weak absorption in the visible region. An increase in the energy band gap for the maximum absorption peak was observed from 3.49 eV for ZnO to 3.88 eV for Zn0.91Cu0.04Co0.05O. The Burstein–Moss effect explained the noticed blue shift in absorption spectra and energy band gaps. The vibrating sample magnetometer study revealed the change in the diamagnetic behavior of pure ZnO to the ferromagnetic behavior of the prepared nanoparticles at room temperature for different doping concentrations. In the current study, we have developed the room-temperature ferromagnetism (RTFM) for Cu and Co co-doped ZnO nanoparticles. Since RTFM is the key objective for dilute magnetic semiconductors, therefore it can be served as the desirable expectant for spintronics applications with improved functionalities and device concepts.

Photocatalytic Dye Degradation and Bio-Insights of Honey-Produced α-Fe2O3 Nanoparticles

Iron oxide nanoparticles are produced using simple auto combustion methods with honey as a metal-stabilizing and -reducing agent. Herein, α-Fe2O3 nanoparticles are produced using an iron nitrate precursor. These prepared samples are analyzed by an X-ray diffractometer (XRD), FTIR spectroscopy, UV-DRS, and a field-emission scanning electron microscope (FESEM) combined with energy-dispersive spectroscopy and a vibrating sample magnetometer (VSM). The XRD results confirm a rhombohedral structure with an R3c¯ space group single-phase formation of α-Fe2O3 in all samples. FESEM images reveal the different morphologies for the entire three samples. TEM analysis exhibits spherical shapes and their distribution on the surfaces. XPS spectroscopy confirms the Fe-2p and O-1s state and their valency. The VSM study shows strong ferromagnetic behavior. The prepared α-Fe2O3 nanoparticles exhibit exceptional charge carriers and radical production. The prepared sample retains excellent photocatalytic, antifungal and antibacterial activity.

Environment friendly synthesis of nickel ferrite nanoparticles using Brassica oleracea var. capitate (green cabbage) as a fuel and their structural and magnetic characterizations

Environment friendly green synthesis, alternate to the chemical approach has been discussed in the current study. Extract of readily available plant, Brassica oleracea var. capitate was used as a natural fuel (reducing and capping agent) to synthesize nickel ferrite (NiFe2O4) nanoparticles by using sol-gel auto combustion method. The samples were calcined at 300 °C and 500 °C. X-Ray diffraction (XRD) analysis was used to confirm the crystalline structure of the synthesized NiFe2O4 nanoparticles. Scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), UV–Visible diffused reflectance spectroscopy (UV–vis DRS), and vibrating sample magnetometer (VSM) analysis were used to interpret the morphological, elemental, optical and magnetic properties of the synthesized nanoparticles. The single phase crystalline nature was revealed by XRD analysis, with average crystallite sizes of 18.16 nm and 24.57 nm. The surface morphology showed the spherical shape with average particle size 26.62 nm and 37.54 nm. Phase purity of the samples were identified using EDX analysis. FTIR was also used to verify the formation of pure phase ferrites. The optical band gap was determined using UV–vis DRS spectra, which was found to decrease from 2.68 eV to 2.64 eV as the calcination temperature was raised. The ferromagnetic property of the samples was clearly demonstrated by VSM studies. The value of saturation magnetization was found to increases from 30.49 emu/g to 35.20 emu/g as the calcination temperature was raised. The increasing trend in coercivity with increasing particle size indicated the single domain ferromagnetic nature of nanoparticles. Additionally a comparison study of all available NiFe2O4 synthesized via green routes was carried out. Better magnetic properties and higher band gap was observed than previously reported NiFe2O4 nanoparticles synthesized by green routes.

Synthesis, characterization, and mechanical properties of oxygen-deficient ferro-diamagnetic transitional barium iron oxide perovskite/polydimethylsiloxane composites

We studied the auto-combustion synthesis and fabrication of an oxygen-deficient perovskite-type barium iron oxide and polydimethylsiloxane (BaFeO3-δ/PDMS) composite and tested its feasibility as a magnetic composite. The perovskite was found to exhibit a polycrystalline nature with polymorphic structural distributions, an altered chemistry, and a completely unusual ferro-to-diamagnetic transitional property, as demonstrated by X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometer studies, respectively. Field emission scanning electron microscopy results revealed that the PDMS completely encapsulated the BaFeO3-δ powder.

Synthesizing and Optimizing Rutile TiO2 Nanoparticles for Magnetically Guided Drug Delivery.

IntroductionTitanium dioxide nanoparticles (TiO2 NPs) have shown tremendous potential in targeted drug-delivery applications. Among various mechanisms, magnetically guided transport of drugs is one such technique for the said purpose. TiO2 NPs being diamagnetic or sometimes exhibiting very weak ferromagnetism can be modified by treating them with suitable magnetic materials.MethodsRutile TiO2 NPs were synthesized and doped with Iron Supplement FericipXT and rare-earth metals like cerium, erbium and neodymium via sol–gel technique. FericipXT-coated rutile TiO2 NPs were synthesized in three different core-shell ratios (1:3, 1:1 and 3:1). The resulting samples were characterized via X-ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and High-Resolution Transmission Electron Microscopy (HR-TEM).ResultsXRD of FericipXT-doped TiO2 NPs showed a rutile phase for 1% and 3% doping; however, only a small fraction of the maghemite phase was obtained for 5% doping. The XRD plots of Ce-doped, Er-doped and Nd-doped TiO2 NPs showed a variety of phases of TiO2 NPs (such as anatase/rutile/mixed) along with the oxide phases of the corresponding rare-earth metal. The presence of various iron titanium oxides and iron oxides was found in core-shell NPs. HR-TEM images confirmed the formation of 1:3, 1:1 and 3:1 core-shell TiO2 NPs. VSM studies showed that the resulting NPs depicted magnetism in the form of superparamagnetism, ferromagnetism and even paramagnetism.DiscussionThe doping to 3% does not affect the original phase of the resulting TiO2 NPs as depicted from the XRD; however, a doping of 5% and more resulted in extra phases corresponding to the dopant added. FericipXT was loaded over TiO2 NPs in amorphous form. Among all the samples synthesized, FericipXT-coated TiO2 NPs demonstrated the best magnetic ability. It was deduced that coating with a magnetic material drastically improves the magnetic character of the host NPs.

Tailoring the Magnetic and Optical properties of MgO Nanoparticles by Cobalt doping

In this work, Cobalt (0-10) % doped MgO nanoparticles are prepared for magnetic and optical studies. X-ray diffraction studies show the particle size increases from 3.10 nm to 9.50 nm with increasing Cobalt concentration in MgO samples. The secondary phases are observed beyond 5% Cobalt in the host MgO which indicates the solubility limit of dopant in this material. SEM analysis further reconfirms the purity and spherical morphology of nanoparticles in all samples. Its result also reveals that the smallest particles have the largest oxygen vacancy concentration as compared to other samples. The dopant and size-induced effects are observed for electronic absorption spectra and bandgap of the samples. UV-visible absorption spectra show a quantum confinement effect as the optical band gap decreases with the increase of the particle size. The optical band gap of the nanoparticles ranges from 4.68 eV to 3.15 eV which is very less in comparison with the bulk MgO band gap up to 7.2eV. Vibrating sample magnetometer studies at room temperature clearly show the ferromagnetic behavior for pure MgO nanoparticles in contrast with the paramagnetic behavior for other samples. It is suggested that the presence of the ferromagnetic behavior in pure MgO nanoparticles are due to the presence of oxygen vacancies.

Vanadium-Doped Molybdenum Diselenide Atomic Layers with Room-Temperature Ferromagnetism.

Diluted two-dimensional magnetic semiconductors with high Curie temperature are highly sought after because of their potential applications in spintronics. Development of new techniques for preparation of high quality diluted magnetic semiconductors is critical for their applications. In this study, vanadium-doped molybdenum selenide, a new diluted magnetic semiconductor, was synthesized by a single-step chemical vapor deposition method. The merit of this method is that the molybdenum and vanadium precursors can be supplied to the growth substrate uniformly. Photoluminescence measurements reveal that the band gap of MoSe2 decreases after doping, which can be attributed to the formation of impurity energy band caused by p-type doping at the valence band maximum. Thus, the V-doped MoSe2 still maintains the semiconducting characteristics. Vibrating sample magnetometer studies clearly show the ferromagnetism of V-doped MoSe2 at room temperature. DFT calculations illustrates the joint contribution of V dopants and nearby atoms to the magnetic moments. This study provides future prospects for the multifunctional application of two-dimensional materials.

Synthesis, structural and magnetic characterization of spherical high entropy alloy CoCuFeNi particles by hydrogen reduction assisted ultrasonic spray pyrolysis

Abstract The present study focuses on the synthesis, structural and magnetic characterization of CoCuFeNi high entropy alloy particles. The hydrogen reduction assisted ultrasonic spray pyrolysis method was used to synthesize nanocrystalline quaternary CoCuFeNi particles in a single step. The effect of synthesis temperature on the structure, morphology and the size of particles was investigated. The syntheses were performed at 700 °C, 800 °C, and 900 °C with 0.1 M concentration of metal nitrate salts precursor solution. The structure and morphology of products were characterized through X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and vibrating sample magnetometer studies. Diffraction pattern based calculations revealed that crystallite sizes of CoCuFeNi particles were in the range of 15.6–26.7 nm. Scanning electron microscopy and energy dispersive spectroscopy investigations showed that particles were agglomerated from crystallites and in spherical morphology with equiatomic elemental composition. According to vibrating sample magnetometry results, soft magnetic properties were observed for CoCuFeNi particles. X-ray photoelectron spectroscopy results showed that the surface has a thin layer of copper oxide.

Physical properties of nanosized (x)NiO/(1−x)CdFe2O4 composites

This study investigates the optical and magnetic properties of nanosized (x)NiO/(1−x)CdFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 1) composites. The samples were synthesized using the wet coprecipitation technique. The X-ray Diffraction patterns demonstrated the formation of Nickel Oxide (NiO) and Cadmium Ferrite (CdFe2O4) phases without any chemical reaction between them. Fourier Transform Infrared results confirm the formation of pure NiO, pure CdFe2O4, and nanosized NiO/CdFe2O4 composites. Transmission Electron Microscopy micrographs show agglomeration between the nanoparticles, demonstrating the magnetic interaction between the oxide and ferrite phases. High-Resolution Transmission Electron Microscopy results verify the presence of NiO and CdFe2O4 phases in each nanosized composite without impurities, which is consistent with the XRD data. The ultraviolet–visible spectroscopy results confirmed that HCl is a better solvent than ethanol in investigating the optical properties of nanosized oxide/ferrite composites. Photoluminescence spectra exhibited asymmetricity owing to the presence of various emission peaks, which reveals the distribution of defect states within the bandgap of the nanosized composites. The Mössbauer spectra of the nanosized composites comprised an asymmetrical doublet at 300 K and an asymmetrical centered doublet within minor sextets at 77 K. Vibrating Sample Magnetometer study showed a shift at 77 K, which can be attributed to the spontaneous exchange bias effect. The magnetic parameters extracted from the M − H loops of all the synthesized nanosized composites at 77 K are higher than those at 300 K.