Augmenting the photocatalytic performance of cobalt ferrite via change in structural and optical properties with the introduction of different rare earth metal ions

In the present study, synthesis of different rare earth (RE) doped cobalt ferrite nanoparticles was done via facile sol-gel auto-combustion method using four different RE metal ions: Eu, Gd, Dy and Nd. The RE substituted cobalt ferrite nanoparticles were then characterized using FT-IR, powder XRD, HR-TEM, SAED, EDX, VSM and DRS techniques. From the characterization results, a significant variation in the structural, magnetic and optical properties of pure cobalt ferrite was observed with the introduction of different RE metal ions. This change in the properties was emerged due to the distortion of the ferrite crystal lattice due to replacement of smaller ionic radii Fe³⁺ ions with the comparatively larger ionic radii RE³⁺ metal ions. The catalytic activity of the fabricated RE doped cobalt ferrite nanoparticles was studied for the photo-Fenton degradation of cationic and anionic dyes. Under visible light irradiation, the as prepared RE doped nanoparticles exhibited great enhancement in the photo-Fenton degradation of dye molecules as compared to pure cobalt ferrite nanoparticles. The enhancement in the degradation rate was ascribed to the generation of defects in the crystal lattice, lower crystallite size and reduced band gap energy values which facilitated the facile transfer of photo-generated holes and electrons. Best catalytic results were obtained for CoNd_0.08Fe_1.92O₄ for SO dye (k?=?2.23?×?10^?1 min^?1) which were found to be around 9 times higher than the pure cobalt ferrite nanoparticles (k?=?0.23?×?10^?1 min^?1).     

Effect of chromium addition on the structural,morphological and magnetic properties of nano-crystalline cobalt ferrite system

Nano-crystalline chromium doped cobalt ferrite powders have been synthesized by PEG assisted hydrothermal route. The structural, morphological and magnetic properties of the products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and vibrating sample magnetometer (VSM). X-ray analysis showed that the samples were cubic spinel. SEM images reveal that the samples' surfaces exhibit well-defined crystalline nanoparticles of spherical shapes with small agglomeration. The addition of Cr³⁺ ions caused a decrease in the average crystallite size, magnetization and the coercive field of the sample. The observed decreases in saturation magnetization and coercivity are explained on the bases of exchange interactions.     

Rietveld structure refinement,cations distribution and magnetic features of CoFe2O4 nanoparticles synthesized by co-precipitation,hydrothermal, and combustion methods

Cobalt ferrite nanoparticles were synthesized by chemical co-precipitation, hydrothermal and sol gel auto-combustion methods. X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM) were used to investigate the structural characteristics and magnetic properties of cobalt ferrite nanocrystals. X-ray patterns revealed the production of a broad single cubic phase with the average crystallite size of 16, 18 and 178 nm for co-precipitation, hydrothermal and combustion methods, respectively. The FTIR measurements between 400 and 4000 cm⁻¹ confirmed the intrinsic cation vibrations of spinel structure. The FE-SEM micrographs of the synthesized samples indicated the presence of two distinct groups of grains exhibiting different sizes and, different shapes for hydrothermal route. The results of magnetic hysteresis at a room temperature showed that the magnetic properties depend on the particle size and shape of particles, whereas the role of particle size is more significant.     

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.     

Morphological,structural, surface,thermal, chemical,and magnetic properties of Al-doped nanostructured copper ferrites

Aluminum-doped copper ferrite nanoparticles synthesized via thermal decomposition were analyzed for Al³⁺ substitution effects. Nanocrystalline doped copper ferrite with a crystallite size <9 nm was characterized using several advanced techniques, including X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The degree of thermal decomposition used for doping copper ferrite at the nanoparticle level correlates well with the quantitative, dimensional, and structural characterizations. The Scherrer equation and Williamson–Hall method were employed to determine the general lattice strain and constants. Structural properties, such as the oxygen positional parameters, radii of the octahedral and tetrahedral sites, hopping lengths, bond lengths and angles, site bonds, and edge lengths, were determined using XRD patterns. The improved A–B super-exchange interaction was demonstrated by the discrepancy in the theoretically anticipated bond angles. The analysis of magnetic hysteresis (M − H) using a vibrating sample magnetometer (VSM) and XPS confirmed the improvement in the super-exchange interaction. XPS results suggest that Fe and Cu in the crystal lattice are in the form of Fe^III and Cu^II, respectively. The investigation of the degree of inversion, state, and composition using XPS aids to understand the properties of the nanostructured copper ferrites. The saturation and remnant magnetization were determined from hysteresis loops at 1.8 T obtained using the VSM at room temperature. The noncollinear spin and efficient sublattice interactions are responsible for the decrease in M_s and M_r.     

Anisotropy investigation of cobalt ferrite nanoparticles embedded in polyvinyl alcohol matrix: A Monte Carlo study

The magnetic properties of the cobalt ferrite/polyvinyl alcohol nanocomposites have been studied experimentally and theoretically. For investigation the impact of polymeric matrix on magnetic properties of magnetic nanoparticles, four different processes have been considered for synthesizing the polymer based nanocomposites by co-precipitation method. The effective magnetic anisotropy obtained by Monte Carlo simulation and law of approach to the saturation magnetization showed a significant decrease relative to the bulk and bare cobalt ferrite nanoparticles. The polymeric matrix interacted with the surface of particles by different strength and made them approximately non-interacting. The as synthesized samples characterized by X-Ray diffractions (XRD) and Fourier transform infrared spectroscopy (FT-IR). Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM).     

Structural,optical, thermoelectrical,and magnetic study of Zn1‐xCoxO (0 ≤ x ≤ 0.10) nanocrystals

In this work, we have prepared Co‐doped ZnO nanocomposites by zinc nitrate and cobalt sulfate as new precursors via the coprecipitation method and the samples were followed to identify the morphological, optical, structural, and magnetic properties. The XRD patterns revealed the crystalline nature of nanoparticles with hexagonal wurtzite structures, which meant that Co impurity did not disturb the structure of pure ZnO and the minimum crystallite size of nanoparticles was calculated to be around 37 nm. The XRD patterns also showed the lattice parameter increase owing to the incorporation of a Co dopant. The TEM results revealed the sphere‐like particles whose size varied between 56 and 88 nm in diameter at a 4% level of impurity. DRS analysis identified that the band gap energy decreased from 3.18 eV for the pure substance to 2.36 eV for the 10% impure substance. VSM analysis exhibited that the saturation magnetization value increased to 8.4 × 10^?3 emu/g for the highest Co content of 10%, which indicated the ferromagnetic behavior of NPs.     

A comparative study of magnetic,photocatalytic and dielectric properties of NiO nanoparticles synthesized by sol-gel and composite hydroxide mediated method

In this study, Nickel oxide (NiO) nanoparticles were synthesized by conventional sol-gel (SG) route using citric acid as an end-capping agent and composite-hydroxide-mediated (CHM) approach. XRD and FTIR confirmed the formation of NiO nanoparticles and the average crystallite size was found to be 68 and 34 nm for SG and CHM method, respectively. Raman spectroscopy revealed higher intensity of one-phonon longitudinal optical (1LO) mode in CHM nanoparticles which is attributed to the presence of defects such as Ni or oxygen vacancies. The two-magnon (2 M) band at 1472 cm⁻¹ confirmed antiferromagnetic (AFM) nature of SG nanoparticles whereas its suppression in CHM nanoparticles indicate superparamagnetic (SPM) nature of the nanoparticles due to decrease in average crystallite size. The magnetic measurements also confirmed the AFM and SPM state of SG and CHM nanoparticles, respectively in accordance with Raman spectroscopy. A sharp and low blocking temperature peak in ZFC/FC also indicates smaller and uniform sized NiO nanoparticles synthesized by CHM method. Optical studies revealed a large value of energy band gap for CHM nanoparticles due to their small average crystallite size and is attributed to quantum confinement effect. A higher photocatalytic performance was observed for CHM nanoparticles due to their large surface area and higher concentration of oxygen vacancies in accordance with Raman spectra. A higher dielectric constant was also observed for CHM nanoparticles due to increased number of grains per unit volume in smaller crystallites. In summary, CHM is one of the most simple synthesis approach that provides fine single-phase NiO nanoparticles at low calcined temperature with improved magnetic, photocatalytic and dielectric properties as compared to SG method.     

Photocatalytic and antibacterial characteristics of decorated polyester textile with ceramic nanoparticles of cobalt ferrite

In this study, a multifunctional textile profiting from photocatalytic activity, magnetic, and antibacterial properties was generated through decorating polyester fabric with cobalt ferrite (CoFe₂O₄) nanoparticles using the co-precipitation technique. The X-ray diffraction (XRD) results supported the successful decoration of fabrics with CoFe₂O₄ magnetic nanoparticles. Field emission electron scanning microscopy (FESEM) images accompanied by energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the morphology, dispersion, and chemical structure of particles on the surface. The mean particle size of cobalt ferrite was measured to be approximately 40 nm. Vibrating sample magnetometer (VSM) results confirmed the ferrimagnetic behavior of the decorated fabrics with saturation magnetization (M_s) and coercivity (H_c) of 1.8 emu/g and 1902 Oe, respectively. The UV–vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) data indicated the appropriate performance under visible light irradiation and postponed electron-hole recombination of the decorated fabric, respectively. The maximum MB degradation efficiency of 97% after 180 min of visible light illumination was obtained. The active species trapping analyses indicated that hydroxyl radicals (^●OH) were the effective species in the photocatalytic degradation mechanism. The decorated sample with the best photocatalytic activity revealed more than 99% reduction in the number of colonies against gram-negative and gram-positive bacteria after 24 h contact time, which validated its excellent potential for antibacterial applications. Outstanding photocatalytic and antibacterial characteristics of the decorated textile with cobalt ferrite nanoparticles turn it into promising composite material for self-cleaning purposes.     

Magnetic properties and hyperfine interactions of Co1-2xNixMnxFe2O4 nanoparticles

Co1-2xNixMnxFe2O4 (0.0≤x≤0.5) nanoparticles (NPs) were prepared via citrate assisted microwave combustion route. XRD analysis confirmed the cubic structure (spinel) of all samples. Average crystallite size of products (obtained from (311) diffraction line) was in the range of 32.9–43.4 nm. The intense peak appearing at around 531 cm⁻¹ in FT-IR was attributed to the formation of a spinel ferrite. Magnetic properties of the products were investigated by room temperature vibrating sample magnetometer and Mössbauer spectroscopy. The magnetic parameters have been found to strongly depend on the Ni and Mn concentrations. The saturation magnetization continuously decreases with the increasing of the concentration (x). We found that Ni_0.5Mn_0.5Fe₂O₄ NP has superparamagnetic character at room temperature. This result was also verified by Mössbauer analysis. Scanning electron microscopic analysis revealed the cubic morphology of all products, EDX and elemental mapping analyses confirmed the expected composition of each product.     

Magnetic properties of MnZn ferrite nanoparticles obtained by SHS and sol-gel autocombustion techniques

MnZn ferrite nanoparticles have been synthesized by self-propagating high temperature synthesis (SHS) and sol-gel autocombustion techniques. The crystallite size, microstructure and magnetic properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. The results showed that single phase manganese ferrite could be achieved directly without any post calcination. However, the crystallite size of the sol-gel autocombusted sample (44 nm) was finer than that of the SHS (57 nm). The SHS synthesized MnZn ferrite with the larger crystallite size exhibited the larger magnetization of 50.6 emu/g than that of 20.9 emu/g for the sol gel autocombusted nanoparticles, despite of its more structure inversity.     

Effect of the rare-earth substitution on the structural,magnetic and adsorption properties in cobalt ferrite nanoparticles

Rare-earth (RE) substituted cobalt ferrite CoFe_1.9RE_0.1O₄ (RE=Pr³⁺, Sm³⁺, Tb³⁺, Ho³⁺) nanoparticles are synthesized by a facile hydrothermal method without any template and surfactant. The effects of RE³⁺ substitution on structural, magnetic and adsorption properties of cobalt ferrite nanoparticles are investigated. Structure, morphology, particle size, chemical composition and magnetic properties of the ferrite nanoparticles are studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), high solution transmission electron microscopy (HRTEM), energy-dispersive spectrometer (EDS), Fourier transform spectroscopy (FTIR), Raman spectra and vibrating sample magnetometry (VSM). The results indicate that the as-synthesized samples have the pure spinel phase, uniform crystallite size and narrow particle size distribution. Meanwhile, the RE³⁺ substitution leads to the decrease in the particle size, magnetization and coercivity of the CoFe₂O₄ ferrite. Notably, it demonstrates that the RE³⁺ doping can apparently enhance the adsorption capacity for Congo red (CR) onto ferrite nanoparticles. Adsorption equilibrium studies show that adsorption of CR follows the Langmuir model. The monolayer adsorption capacities of CoFe_1.9Sm_0.1O₄ and CoFe_1.9Ho_0.1O₄ are 178.6 and 158.0 mg/g, respectively. The adsorption kinetics can be described by the pseudo-second-order model.     

Microwave combustion synthesis,magneto-optical and electrochemical properties of NiMoO4 nanoparticles for supercapacitor application

Nickel molybdate (NiMoO₄) nanoparticles (NPs) were synthesized by a simplistic one-pot microwave combustion method using urea as the fuel. The produced NPs have been examined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) analysis, scanning electron microscope (SEM), energy dispersive X-ray (EDX), high-resolution transmission electron microscopy (HR-TEM) analysis. Further, optical and electronic properties were determined by UV-Visible and Photoluminescence (PL) analysis, respectively. The magnetic performance of the NiMoO₄ NPs was investigated by vibrating sample magnetometer (VSM) and the surface chemical composition was identified by X-ray photoelectron spectroscopy (XPS). The electrochemical activities of the NiMoO₄ NPs were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD) analysis. From the results, the CV curves indicated the occurrence of redox couples and besides with the EIS data (Nyquist plot), confirmed the supercapacitor nature of the synthesized NiMoO₄. The prepared NiMoO₄ exhibits a high specific capacitance and rateability. This electrode grants a high specific capacitance of 450?F?g^?1 at 2?mA?cm^?2 and the well permanency with a cycling proficiency of 94% after 1000 cycles. These results clearly showed that the synthesized NiMoO₄ NPs have potential application for the forthcoming flexible and lightweight energy storage.     

Effects of magnesia addition on structural, morphological and magnetic properties of nano-crystalline nickel ferrite system

Nano-crystalline magnesia doped nickel ferrite powders have been synthesized by the combustion route. The structural, morphological and magnetic properties of the products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and vibrating sample magnetometer (VSM). X-ray analysis showed that all samples were cubic spinel. The increase in magnesia concentration resulted in a decrease in the average crystallite size, lattice constant, unit cell volume, X-ray density, ionic radii, the distance between the magnetic ions and bond lengths on tetrahedral sites and octahedral sites of the as prepared ferrite. The combustion method led to formation of spongy and fragile network structure. Increasing amounts of magnesia brought about remarkable changes in the microstructure and porosity of nickel ferrite. Doping of nickel ferrite by magnesia led to a decrease in its saturation magnetization. The minimum saturation magnetization value of nickel ferrite due to the doping 1 wt.% MgO attained 44.18 emu/g.     

Microstructural,magnetic, and hyperfine characterizations of Cu-doped cobalt ferrite nanoparticles

We have investigated the structural and magnetic properties of polycrystalline Cu-substituted cobalt ferrite (Cu_xCo_1−xFe₂O₄: x = 0.00, 0.15, 0.30, 0.45, 0.60) nanoparticles, synthesized via chemical coprecipitation method. The prepared samples were of single phase as confirmed by X-ray diffraction analysis. The mean crystallite size ranged from 44 to 65 nm was obtained using Scherrer's formula. M-T curves revealed that the Curie temperature of all the samples was above room temperature and it was found to decrease with increasing Cu concentration, which was supported by Mössbauer spectra. Field cooled (FC) hysteresis curves showed ferrimagnetic nature at 5 K and room temperature. It was observed that careful variation of Cu concentration in cobalt ferrite lead to weak A-B interaction with tunable magnetic properties.     

Erbium substituted nickel–cobalt spinel ferrite nanoparticles: Tailoring the structural,magnetic and electrical parameters

In this article, we have reported an effective, rapid as well as economical Er³⁺ substituted Ni_0.4Co_0.6Fe₂O₄ ferrite nanoparticles synthesized via surfactant-assisted co-precipitation route. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), dielectric properties, current-voltage (I–V) measurements, and vibrating sample magnetometry (VSM). XRD and FTIR confirmed the face-centered (FCC) spinel structure of all compositions of the synthesized spinel ferrite nanoparticles. The deviations in the lattice constant granted with the variation in size of the guest (Er³⁺) and host (Fe³⁺) cations. These ferrites were also subjected for electrical, magnetic and dielectric investigations. I–V measurements showed that resistivity values decreased from 6.20 × 10⁷ Ω cm to 0.03 × 10⁷ Ω cm with the increased Er³⁺ contents. Saturation magnetization increased from 35.99 to 39.95 emu/g. This high value of saturation magnetization suggested the possible utilization of such ferrites for practical applications such as microwave and recording devices fabrication. Interestingly, the magnetic and dielectric properties of nickel-cobalt ferrite nanoparticles showed ample improvement upon Er³⁺ substitution. The results clearly indicate the potential of Er⁺³ substituted spinel ferrite particles in various advanced technological devices fabrication.     

Water-Dispersible Pd–N-Heterocyclic Carbene Complex Immobilized on Magnetic Nanoparticles as a New Heterogeneous Catalyst for Fluoride-Free Hiyama,Suzuki–Miyaura and Cyanation Reactions in Aqueous Media

Catalysis Letters - Pd–N-heterocyclic carbine complex immobilized on magnetic nanoparticles is synthesized and characterized by different techniques such as FT-IR, XPS, TEM, EDX, FESEM, VSM,...     

Structural,magnetic and catalytic properties of La2-xBaxCuO4 (0 ≤ x ≤ 0.5) perovskite nanoparticles

Barium doped La₂CuO₄ perovskite nanoparticles were synthesized via microwave assisted combustion method. The effects of Ba²⁺ doping on structural, optical, magnetic and catalytic activity of La₂CuO₄ have been studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and vibrating sample magnetometer (VSM) techniques. The XRD patterns of pure La₂CuO₄ and La_1.9Ba_0.1CuO₄ confirmed the formation of perovskite structure without impurities. However, with increasing Ba²⁺ content in the range 0.2–0.5, phase transformation from orthorhombic to tetragonal structure, occurred. The average crystallite size of orthorhombic and tetragonal phases were in the range 45.2–52.2?nm and 0.5–41?nm, respectively. The appearance of FT-IR bands at around 685 and 517?cm^?1 were correlated to the La-O and Cu-O stretching modes of orthorhombic La₂CuO₄ phase. The direct band gap estimated using Kubelka–Munk (K–M) method decreased with the increase in Ba²⁺ content (1.88–1.64?eV), due to the formation of sub-bands in the energy band gap. Magnetic measurements of doped La₂CuO₄ samples showed either para- or ferro-/para- magnetic behaviour at room temperature. The catalytic activity (oxidation) tests carried out in a batch reactor operating under atmospheric conditions indicated that the prepared catalysts, in particular (La_1.7Ba_0.3CuO₄), showed excellent catalytic activity.     

Effect of La-Ni substitution on structural,magnetic and microwave absorption properties of barium ferrite

In this paper, La-Ni substituted barium ferrite nanoparticles were prepared by a co-precipitation method. The morphology, structure, magnetic and microwave absorption properties of samples were accomplished by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analysis. From the results evaluation, it can be seen that the magnetoplumbite structure for all of the samples have been formed and the average crystallite sizes of Ba_1−xLa_xFe_12−xNi_xO₁₉ nanoparticles within in the range of 50.9–65.5 nm. Ba_0.9La_0.1Fe_11.9Ni_0.1O₁₉ exhibits a remarkable reflection loss of −13.5 dB at 13.05 GHz with a matching thickness of 1.5 mm. The reflection loss results indicate that Ba_0.9La_0.1Fe_11.9Ni_0.1O₁₉ nanoparticles may be used as a potential for thin microwave absorbers.     

Synthesis and magnetic properties of nano-sized Cu0.5Ni0.5Fe2O4 via citrate and aloe vera: A comparative study

In this report, Cu_0.5Ni_0.5Fe₂O₄ nanoparticles were synthesized by solgel using eco-friendly aloe vera extract and citric acid separately and their properties were discussed. Structural, Functional, morphological, magnetic properties of the samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM). XRD exhibited the samples have single phase cubic spinel with average size of 46.4?nm and 35.45?nm. Two characteristics bands of ferrite were confirmed by FTIR. TEM indicated different morphology of the samples with some regularity. VSM data showed that higher coercivity for the sample prepared by aloe vera extract.