Substituted Cobalt Ferrite Nanoparticles Research Articles

Tailoring the structural, magnetic and dielectric properties of cobalt ferrites by chromium substitution

Ferrites are renowned for their extensive use in a variety of industries, from manufacturing to the biomedical field. In the current study chromium substituted cobalt ferrite nanoparticles (CoCrxFe2-xO4,x = 0, 0.25, 0.5, 0.75, and 1) were synthesized by utilizing the sol–gel auto combustion method. Various analytical tests confirm the effect of Cr doping concentration on cobalt ferrites. The structural and morphological analysis of samples were done using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) respectively. The samples' pure spinel structure was confirmed by XRD analysis. Magnetic characterization at room temperature and low temperature were carried out using Quantum Design's PPMS. The dielectric properties of the samples were examined using a Hioki 3532 LCR hitester. The results demonstrate the effect of chromium substitution in cobalt ferrites and suggest the possible uses of the prepared samples.

Temperature annealing dependence of structural, magnetic, and antibacterial properties of silver substituted cobalt ferrite nanoparticles produced by coprecipitation route

In this study, silver-substituted cobalt ferrite (Ag0.02Co0.98Fe2O4) nanoparticles were successfully sensitized by the coprecipitation method. Annealing temperature treatment was used to modify the physical properties, i.e., 200 °C, 300 °C, 400 °C, and 500 °C. XRD analysis showed an increase in the annealing temperature, the crystallite size increased from 19.78 to 24.11 nm, and the grain size increased from 54.75 to 61.39 nm. The FTIR spectrum showed two prominent absorption bands around k ∼577 and k ∼381 cm−1, allowing metal oxide absorption in the tetrahedral and octahedral sites. There is a redistribution of cations which is more significant at the tetrahedral sites than at octahedral sites, toward a perfect spinel structure. An increased annealing temperature increased the saturation magnetization and coercive field from 31.80 to 50.60 emu g−1 and 651 to 1,077 Oe, respectively, attributable to an increase in the magnetocrystalline anisotropy constant. The evaluation of S. aureus and E. coli showed that Ag0.02Co0.98Fe2O4 indicated the zone of inhibition (ZOI) around the disks due to its antibacterial properties. The most significant on S.aureus and E.coli were 12.73 mm (mortality of 88%) and 12.43 mm (mortality of 80%), respectively, for Ag0.02Co0.98Fe2O4 annealed at 200 °C that have the minor grain size materials.

Synthesis of Zinc Substituted Cobalt Ferrite Nanoparticles by Using Sol-Gel Method as Antibacterial Material

The synthesis of zinc-substituted cobalt ferrite (Co0.9Zn0.1Fe2O4) using the sol gel method has been successfully carried out. The thermogravimetric analysis and differential thermal analyzer curve shows that at 400°C the Co0.9Zn0,1Fe2O4 sample has formed the final phase of nanoparticles. Therefore, the modification of physical properties was carried out by annealing treatment at temperature of 450°C, 550°C, 650°C, and 750°C. The X-rays diffraction show that all samples are in a single phase with a face center cubic space group Fd-3m structure according to the ICDD 221086. The crystal size increased with the annealing temperature 33.69 nm to 45.88 nm. The Co0.9Zn0.1Fe2O4 showed as excellent antibacterial properties on Staphylococcus aureus and Escherichia coli. The most superior antibacterial activity to Staphylococcus aureus was Co0.9Zn0,1Fe2O4 sample which was annealed at 650°C with a clear zone diameter of 39.81 mm. Meanwhile, the Escherichia coli bacteria which had the most superior antibacterial activity were Co0.9Zn0,1Fe2O4 samples which were annealed at 450°C with a clear zone measuring 21.04 mm.

Synthesis of Ni0.5Co0.5Fe2O4 Ferrite and Effect of Annealing Temperature on the Structural, Morphological and Dielectric Analysis

In the current work, we have synthesized nickel substituted cobalt ferrite nanoparticles using Pechini's method. The presence of single-phase synthesized nanoparticle is confirmed at annealing temperature around 1000 oC and the crystallinity nature further improves at 1150 oC. The average crystallite size is found to increase with increasing annealing temperature. The strain in the crystalline particles also found to decrease with increasing temperature as confirmed through XRD analysis. The cuboidal morphology with considerable size is observed in nanoparticles by FESEM images. The EDAX spectrum further confirms the presence of pure single phase of desired elements in grown nanoparticles. The dielectric properties were studied using impedance spectroscopy, recorded from 100 Hz to 1 MHz at room temperature for different annealed temperatures. The change in the frequency dependent dielectric properties with increasing annealing temperature are in accordance with the Maxwell-Wagner two layers model for space charge theory and correlated barrier hopping (CBH) model.

Observation of dielectric dispersion and relaxation behavior in Ni2+-substituted cobalt ferrite nanoparticles

Combined experimental and theoretical analysis reveals the superior properties of Co1−xNixFe2O4 nanoparticles – a putative candidate for energy-harvesting applications.

Temperature Annealing Dependence of Structural, Magnetic, and Antibacterial Properties in Silver Substituted Cobalt Ferrite Nanoparticles Produced by Coprecipitation Route

Temperature Annealing Dependence of Structural, Magnetic, and Antibacterial Properties in Silver Substituted Cobalt Ferrite Nanoparticles Produced by Coprecipitation Route

Dielectric and Magnetic Studies La+3 doped Cobalt Nano Ferrite

La3+ substituted cobalt ferrite nano-particles with the chemical composition LaxCoFe2-xO4 (here,x=0, 0.05, 0.1, 0.15 and 0.2) were synthesized using auto-combustion method. Structural and morphological studies were probed using X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). Formation of rare-earth doped cobalt ferrite was confirmed using the X-ray diffraction studies. Average crystallite size (D) was found to be varying from 43.71nm to 55.37nm with the increase in La3+ concentration. Frequency dependent dielectric properties of synthesized samples were measured from 100 Hz to 1 MHz at room temperature using a precision HIOKI make LCR HI-TESTER. Dielectric dispersion was observed at lower frequencies for the synthesized samples. Magnetic properties were studies using Vibrating Sample Magnetometer (VSM), all the synthesized samples exhibited well defined magnetic hysteresis curves, there by confirming the magnetic behaviour of the sintered samples.

Low temperature rapid sol–gel auto-combustion synthesis and structural, morphological and magnetic study of nickel substituted cobalt nano ferrites

ABSTRACT The nickel substituted cobalt ferrite nanoparticles were synthesized via the sol–gel auto-combustion method. The single cubic spinel structure formation was confirmed from X-ray diffraction and Fourier transforms infrared spectroscopy study. The effect of lattice strain on crystalline size was studied using Williamson–Hall and the size-strain plot method. A microstructural study was performed using high-resolution field emission scanning electron microscopy. The magnetic properties were studied at room temperature using a vibrating sample magnetometer. The saturation magnetization obtained for pure cobalt nano ferrite was 79.66 emu/g comparable with the value for the bulk sample. The anisotropic constant and anisotropy field were found to be erg/cm3 and 88.66 kOe respectively for pure cobalt ferrite. The high value of saturation magnetization, anisotropic constant and anisotropy field of cobalt ferrite are important parameters for the application of prepared samples in data recording devices.

Laser assisted hydrothermal synthesis of magnetic ferrite nanoparticles for biomedical applications

In this work, copper substituted cobalt ferrite nanoparticles Co1-xCuxFe2O4 (×=0, 0.3, and 0.7), has been synthesized via laser assisted hydrothermal synthesis (LAHS) methods. The XRD patterns showed single phase spinel structure, comparative study between the two preparation methods, effect of laser irradiation on the structural properties, and average crystallite size that is evaluated from most intense peak (311) utilizing Scherrer formula. Further studies for laser assisted hydrothermal as-prepared ferrite samples using each of Field emission-scanning electron microscope (FE-SEM) which revealed the study of topography, shape, particle size, vibrating sample magnetometer (VSM) with in 15kOe as maximum field. That was used to study the magnetic properties and confirmed the super-paramagnetic property of the prepared ferrite nanoparticles. Coercivity (Hc), remanence (Mr), saturation magnetization (Ms) and sequarness ratio were directly extracted from hysteresis loops. Moreover, results showed that the magnetic characteristics are on the basis of each particle size as well as cation distribution. In addition, the antibacterial property of the prepared nanoparticles against S. aureus and E. coli found to be improved after substitution of Cu in Co ferrite matrix.

Structural, morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles

In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural, morphological and dielectric properties are reported. Zirconium substituted cobalt ferrite Co1-xZrxFe2O4 (x = 0.7) nanoparticles were synthesized by sol-gel route. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope (HRSEM) analysis are reported. Scherrer plot, Williamson–Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The atoms vibration modes of as synthesized nanoparticles were recorded using Fourier transform infrared (FTIR) spectrometer in the range of 4000–400 cm-1. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out. Relative dielectric permittivity, loss tangent and AC conductivity were measured in the frequency range 50 Hz to 5 MHz at temperatures between 323 and 473 K. The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal.

Effect of metal substitution (Zn, Cu and Ag) in cobalt ferrite nanocrystallites for antibacterial activities

Metals-substituted cobalt ferrite nanocrystallites with nominal composition of Co1-xMxFe2O4 (M = Zn, Cu, Ag; x = 0.2) were synthesized by a sol–gel auto combustion method. The crystal structure, morphological, elemental composition and magnetic properties of the samples were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman Spectroscopy, High resolution scanning electron microscopy (HRSEM), Energy dispersive X-ray spectroscopy (EDX), and Vibrating sample magnetometer (VSM) analysis. XRD pattern confirm the single phase cubic spinel structure of the synthesized particles with size varying from 13 to 19 nm. The Scherer and Williamson-Hall (W-H) method were applied to determine crystallite size and strain present in the sample. The FT-IR spectra showed the existence of metal–oxygen stretching bands. The antibacterial activity of transition metal-substituted cobalt ferrite nanoparticles against the six bacteria were qualitatively measured by performing well diffusion test. The results revealed that Cu substituted cobalt ferrite nanoparticles exhibit higher antibacterial activity than other substituents (Ag and Zn) which could be used in drug delivery systems as well as in other biomedical and biotechnology applications.

Effect of Magnesium Substitution on Structural, Magnetic and Biological Activity of Co(1-x)Mg(x)Fe2O4 Nano-colloids

Citrate coated magnesium substituted cobalt ferrite nanoparticles Co(1-x)Mg(x)Fe2O4 (where, x = 0.0, 0.25, 0.50, 0.75, 1.0) were prepared by sonochemical method. X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy and Fourier transform infrared spectroscopy results confirmed the formation of spinel structures for all concentration values of substitution (x = 0.0–1.0). Furthermore, saturation magnetization was decreased upon increasing magnesium content. Hemolysis assay in vitro confirmed safety of nanoparticles for systemic administration and was non-significant upon increasing magnesium content when compared to untreated control. In vitro cytotoxicity screening against HepG2 cells revealed that cytotoxicity had an inverse relation with increasing magnesium concentration. Highly significant result was observed in the presence of x = 0.25 with percentage viability of 33.5 ± 2.28%. Similarly, antibacterial studies showed highly significant bacterial inhibition against pathogenic strains in the presence of x = 0.25. The results reveal the optimal value of magnesium co-doped functional magnetic materials and their application in biomedicine.

Improved Electrical Properties Displayed by Mg2+-Substituted Cobalt Ferrite Nano Particles, Prepared Via Co-precipitation Route

In this reported study, magnesium-substituted cobalt ferrite nanoparticles (Co1−xMgxFe2O4, x = 0.0, 0.20, 0.35, 0.50) have been investigated. The samples were prepared via a wet chemical co-precipitation route and were calcinated at 800 °C for 6 h. The structural, electrical, and dielectric properties of these samples were studied using XRD, SEM, FTIR, impedance analyzer, and LCR meter. The XRD diffractograms established the development of FCC spinel arrangement with decreasing crystallite size from 20 to 30 nm without any additional impurity peak confirming the purity of the samples synthesized. The FTIR spectra established the existence of tetrahedral (A) and octahedral (B) lattice sites in the structural arrangement. The SEM images showed uniform nano-spherical particle formation with minimum porosity. No extra phase or impurity was found, confirming the effectiveness of the co-precipitation route. The dielectric properties of the synthesized samples measured at ambiance temperature against frequency range of 103 Hz to 5 MHz showed massive enhancement of dielectric constant (on the order of 104 at 100 Hz) which was comparable to traditional ceramics (having a dielectric constant in the range of 104–106), which are often rendered suitable for capacitor applications. Furthermore, the low values of dielectric loss tangent at high frequencies verified its potential usage in microwave applications. A significant contribution of both long- and short-range order in hopping as well as an increase in grain boundary density was confirmed by complex electric modulus analysis. The DC electrical resistivity measurement against increasing temperatures was done, showing a typical decreasing trend with increasing temperature, validating the semiconductor nature of synthesized nanoparticles with varying compositions. The drift mobility was further calculated from the DC resistivity data.

Effect of Gd3+ substitution on proton relaxation and magnetic hyperthermia efficiency of cobalt ferrite nanoparticles

In this study, Gadolinium substituted Cobalt Ferrite nanoparticles (CoFe2-xGdxO4, 0 ≤ x ≤ 0.4) were prepared via hydrothermal route using triethylamine as reducing agent at 180°C for 12 h. X-ray diffraction studies revealed the single phase cubic spinel structure for both Cobalt ferrite (CF) and Gadolinium substituted Cobalt Ferrite (CFG) nanoparticles (x ≤ 0.24). An increase in the Specific absorption rate (SAR) was observed with increase in Gd concentration. Further with increase in the molar concentration (x > 0.24), gadolinium hydroxide was observed as the secondary phase, which was also confirmed by the Gd–O stretching vibrations observed in Fourier transform Infrared spectroscopy. The evolution of Gadolinium hydroxide showed a strong influence in the relaxivity (r1) and hyperthermia potential. Field emission scanning electron microscopy revealed that CF and CFG (x ≤ 0.24) nanoparticles were spherical in nature with particle size ranging from 10 to 25 nm, whereas the particle size increases above 30 nm for CFG (0.3 ≤ x ≤ 0.4) nanoparticles along with the presence of columnar shaped particles. Magnetic measurements confirmed the pseudo single domain, ferri-magnetic nature of CF and CFG nanoparticles. The magnetization data revealed a change in direction of magnetization towards easy axis with increasing Gd concentration. The orientation of magnetization direction towards easy axis had induced change in the hyperthermia potential. Proton relaxation studies of CF and CFG nanoparticles revealed that there is a strong interaction between the relaxivities r1 and r2. The specific absorption rate of CF and CFG nanoparticles were observed to be in the range from 91.49 W g−1 to 232.17 W g−1 at applied Hf of 4.19 × 109 Am−1 s−1.

Synthesis and Characterisation of Copper Substituted Cobalt Ferrite Nanoparticles by Sol-Gel Auto Combustion Route

In the present study, the structural, functional, morphological and magnetic characteristics of copper substituted cobalt ferrite nanoparticles were investigated. The samples of Co1-xCuxFe2O4 at x = 0.06, 0.08 and 0.1 M were prepared by Sol-gel auto combustion route. X-ray diffraction technique was used to confirm the phase formation and structural analysis which matches with the JCPDS Data. The average crystallite size was found to be ∼25, ∼19 and ∼18 nm for x = 0.06, 0.08 and 0.1 respectively. The Micro Raman Spectroscopy revealed the stretching vibrations at 274 cm−1, 660 cm−1, and 466 cm−1, which are characteristic of Spinel Ferrites. From the FTIR analysis, the band observed at 3457cm−1 and 1650 cm−1 is assigned to hydrogen bonded O-H group and ionic stretching of C-H bond. The band assigned at 1105 cm−1, is due to Co – O and Cu - O or Fe – O vibrations. The existence of water adsorption band and metal oxygen band confirms the existence of Co and Cu in the synthesized sample. The surface morphology of samples was imaged by the field emission scanning electron microscope. The substitution of Cu2+ in the parent systems caused a significant reduction in particle size. The compositional analysis was done, which confirmed that the concentration of copper was increased in the samples. The samples were subjected to magnetic characterization because magnetic behavior is also affected by substitution of Copper in Cobalt ferrite. Magnetic hysteresis study at room temperature confirmed the reduction in saturation magnetization (MS = 14.25 to 8.33 emu/g.) and reduction in coercivity (HC = 602.64 to 380.94 Oe) when size is reduced. As the concentration of Cu into CoFe2O4 matrix increases, particle size decreases and the saturation magnetization decreases.

Structural and Magnetic Studies of Zinc Substituted Cobalt Ferrite Nanoparticles prepared by Sol–Gel Technique

All Magnetic nanoparticles are newly explored materials due to its large surface to volume ratio, smaller grain size, quantum confinement effect, large uni-axial anisotropy and superparamagnetism. In the present study, Zinc substituted cobalt ferrite nanoparticles are prepared by sol-gel auto-combustion method with copper concentration varies from 0.0 to 0.0. Structural studies are taken by XRD, it was confirmed that the sample has pure cubic spinel phase structure and the crystallite size decreases from 25nm to 15nm as the Zn content increases. Raman spectroscopy confirming the spinel structure and in the case of Co1-xZnxFe2O4, the Raman bands show a shoulder-like feature at the lower wavenumber which are Raman active bands in Fe3O4 all the tetrahedral and octahedral sites are occupied by Fe ions. From FTIR Analysis, the peak observed at 433 cm−1 and around 580 cm−1 it confirms the metal oxygen vibration at octahedral and tetrahedral site. Morphological analysis shows that the spherical sized particles with pores due to the evolution of gases during the annealing process at higher temperature. The magnetic studies reveals that as the ratio of metal nitrates increases, the coercivity and remanence decreases following a hysteresis path. By the above characterization technique we were successfully able to confirm the substitution of Zinc in the octahedral sites of cobalt ferrite.

Antibacterial and Antifungal Activity of Novel Synthesized Neodymium-Substituted Cobalt Ferrite Nanoparticles for Biomedical Application

Neodymium (Nd)-substituted cobalt ferrite nanoparticles (NPs), i.e., CoNdxFe2−xO4 (0.0 ≤ x ≤ 0.2) NPs, were synthesized by the sonochemical method. The compositional characterization was done by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Antistaphylococcal activity was found to be enhanced, i.e., survival rate was 50%, 45%, 40%, and 30% with the increase in the ratio of Nd (0.0 ≤ x ≤ 0.2), whereas anticandidal activity was found efficient, i.e., 9%, 20%, 22%, and 40% survival rate at all the four ratios. The morphogenesis studies indicated that the synthesized metal–ligand, improves the antimicrobial capacity by binding them strongly to the microbial walls. To the best of our knowledge, this is the first report which demonstrates the series of CoNdxFe2−xO4 (0.0 ≤ x ≤ 0.2) NPs being active towards Staphylococcus aureus and Candida albicans and encourages its potential candidature for pharmaceutical and biomedical purposes.

Dielectric, impedance, AC conductivity and low-temperature magnetic studies of Ce and Sm co-substituted nanocrystalline cobalt ferrite

Abstract In this study, we report frequency and temperature dependent dielectric, electrochemical impedance and low temperature magnetic properties of Sol-gel auto-combustion synthesized rare-earth (Ce and Sm) co-substituted cobalt ferrite, CoCexSmyFe2-x-yO4 (x = y = 0.00, 0.1, 0.12 and 0.25). The surface morphology and particle size as obtained by XRD studies was confirmed by HRTEM measurements for a representative sample. The dielectric properties such as dielectric constant, loss tangent and AC conductivity have been measured using LCR meter, variation of dielectric parameters with substituent concentrations, frequency range from 0.1 to 10 MHz at room temperature (RT) and temperatures 100–400 °C have been well supported by Maxwell-Wagner interfacial polarization. The AC conductivity increased with applied frequency suggesting that the conduction mechanism is owing to small polaron hopping between cations. Impedance studies shows that, the addition of RE (Ce and Sm) cause a decrease in the Z′ value, with increasing frequency which can be attributed to the space charge polarization effect in the material. Low temperature magnetic measurements in ZFC-FC mode and magnetic isotherms at 20 and 310 K reveals the ferromagnetic nature of RE (Ce, Sm) substituted cobalt ferrite nano particles. The coercive field has been increased at low temperature 20 K compared to that at 310 K, the samples shows super paramagnetism beyond room temperature.

Synthesis and structural characteristics of Co1-xCuxFe2O4 magnetic ferrite nanoparticles using hydrothermal technique

In this work, copper substituted cobalt ferrite nanoparticles withchemical formula Co1-xCuxFe2O4 (x=0, 0.3, and 0.7), has beensynthesized via hydrothermal preparation method. The structure ofthe prepared materials was characterized by X-ray diffraction (XRD).The (XRD) patterns showed single phase spinel ferrite structure.Average crystallite size (D), lattice constant (a), and crystal density(dx) have been calculated from the most intense peak (311).Comparative standardization also performed using smaller averageparticle size (D) on the XRD patterns of as-prepared ferrite samplesin order to select most convenient hydrothermal synthesis conditionsto get ferrite materials with smallest average particle size.

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 CoNd0.08Fe1.92O4 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).