Formation Of Spinel Structure Research Articles

Effects of Lanthanum Substitution and Annealing on Structural, Morphologic, and Photocatalytic Properties of Nickel Ferrite.

Nanoparticles of NiLaxFe2-xO4 ferrite spinel incorporated in a SiO2 matrix were synthesized via a sol-gel method, followed by annealing at 200, 500, and 800 °C. The resulting materials were characterized via XRD, AFM, and BET techniques and evaluated for photocatalytic activity. The XRD diffractograms validate the formation of a single-phase cubic spinel structure at all temperatures, without any evidence of secondary peaks. The size of crystallites exhibited a decrease from 37 to 26 nm with the substitution of Fe3+ with La3+ ions. The lattice parameters and crystallite sizes were found to increase with the rise in La3+ content and annealing temperature. Isotherms were employed to calculate the rate constants for the decomposition of malonate precursors to ferrites and the activation energy for each ferrite. All nanocomposites have pores within the mesoporous range, with a narrow dispersion of pore sizes. The impact of La content on sonophotocatalytic activity was evaluated by studying Rhodamine B degradation under visible light irradiation. The results indicate that the introduction of La enhances nanocomposite performance. The prepared Ni-La ferrites may have potential application for water decontamination.

Facile production of Ag-Co3O4/rGO nanocomposite and its enhanced photocatalytic and electrochemical activities for practical applications

In this study, authors produced Co3O4, Ag-Co3O4 nanoparticles and Ag-Co3O4/rGO nanocomposites through a facile, one-step and cost-effective hydrothermal route; and thoroughly analyzed these materials using a variety of complementary techniques, including XRD, SEM/TEM, XPS, FTIR, VSM, UV–Vis, PL, photocatalytic and electrochemical measurements. The formation of cubic spinel structure in Ag-Co3O4/rGO nanocomposite was investigated by X-ray diffraction. The estimated average crystalline size in case ofCo3O4, Ag-Co3O4, and Ag-Co3O4/rGO samples was found to be 11.2, 14.1 and 17.5 nm, respectively. As a comparison to Co3O4 and Ag-Co3O4 nanoparticles, the absorption edge of Ag-Co3O4/rGO nanocomposite was significantly shifted towards the visible region, and hence the band gap is narrowed due to highly conducting Ag and rGO incorporation. The photo-generated electrons and holes were rapidly transferred from Co3O4 to Ag and rGO, leading to reduced PL intensity ofAg-Co3O4/rGO nanocomposite. Authors evaluated the photocatalytic efficiency of synthesized Ag-Co3O4/rGO nanocomposite, which exhibited an enhanced photodegradation potential against RhB dye. Authors also examined the electrochemical activity of as-obtained Ag-Co3O4/rGO nanocomposite using cyclic voltammetry and galvanostatic charge-discharge cycle analysis, demonstrating its employability in supercapacitors as it possessed excellent specific capacitance.

Dielectric and thermal behavior investigation of Mn-Zn nano ferrite-fluid for transformer oil applications

Manufacturing of novel transformer oil-based nanofluids has become necessary to improve dielectric and cooling properties. The current study was carried out to examine the dielectric and thermal characteristics of transformer oil incorporated by Mn0.5 Zn0.5 Fe2O4 nanoparticles (Mn-Zn ferrite NPs) that were synthesized by an auto-combustion technique. The microstructure and morphology of the synthesized Mn-Zn ferrite NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and high-resolution transmission electron microscopy (HRTEM). The formation of a single-phase cubic spinel structure for the Mn-Zn ferrite NPs was confirmed by XRD results. The average crystallite sizes of about 26.7 nm obtained from XRD are very close to the measured value obtained from HRTEM. VSM measurements ensure a high saturation magnetization of 57 emu/g for the Mn-Zn ferrite sample and which makes it a very good candidate as a transformer oil filler. The as-synthesized Mn-Zn ferrite NPs were then introduced into transformer oil with concentrations up to 0.4 g/L to form Mn-Zn nano ferrite-fluid. The dielectric properties of the prepared nano ferrite-fluid samples were investigated by measuring the dielectric constant (ε′) and dissipation factor (tan δ) in the frequency range of 30 Hz − 1 MHz. Moreover, the AC breakdown voltage of the investigated nano ferrite-fluid samples was measured at a constant 500 V/s ramp, and it showed a pronounced enhancement with the addition of Mn-Zn ferrite NPs. It reached 80 % for 0.2 g/L of NPs. Moreover, the convective heat transfer of the nano ferrite-fluid was examined through the heating–cooling process, which is indicating a significant reduction in the thermal time constant in cooling with the introduction of the Mn-Zn ferrite NPs into the oil.

Synthesis and characterization of structural, magnetic and electrical properties of Mn substituted Co-Zn ferrite

Spinel – type Zn0.5Co0.5 - xMnxFe2O3 ferrites were synthesized via solid-state reaction method with x values of 0.0, 0.1, 0.2, 0.3, and 0.4. X-ray diffraction was used to identify the crystallographic structure, which revealed the formation of a single-phase cubic spinel structure. The lattice parameter of Co-Zn ferrite samples was measured with a maximum value of 8.76 Å, and the density decreased with increasing concentration. The average grain size decreased with increasing Mn concentration. The Vibrating sample magnetometry (VSM) technique confirmed the soft ferromagnetic character of the entire sample, with a maximum magnetic saturation value of 73.67 emu/g, which was decreased with increasing Mn concentration. The magnetic coercivity (Oe) value led to a slightly hard magnetic phase with increasing Mn concentration, with a maximum value of 6.22. AC resistivity and permeability decreased with increasing frequency but were more activated at lower frequency, which is typical for ferrite behavior. The resistivity and dielectric constant correlated with the value of porosity and bulk density with increasing Mn percentage.

Facile synthesis of ternary g-C3N4/polyacrylic acid/CoFe2O4 nanocomposites for solar light irradiated photocatalytic and supercapacitor applications

The present work reports an enhanced photocatalytic and electrochemical performance of g-C3N4 assisted PAA on CoFe2O4 (g-C3N4/PAA/CoFe2O4) ternary nanocomposites (NCs). XRD analysis confirms the formation of a single-phase cubic spinel structure of CoFe2O4. The recombination of photogenerated charge carriers is greatly inhibited by the incorporation of PAA and g-C3N4 on CoFe2O4 and thus improves their separation efficiency. The size and size distribution of the pristine CF NPs is considerably influenced by the incorporation of PAA and g-C3N4 which was confirmed by SEM and TEM analysis, respectively. The ternary NCs (g-C3N4/PAA/CoFe2O4) exhibit superior photocatalytic degradation (91%) against crystal violet dye under direct solar light irradiation when compared with binary PAA/CoFe2O4 (79%) NCs and pristine CoFe2O4 (32%) NPs. GCD measurement shows that g-C3N4/PAA/CoFe2O4 NCs exhibits a high specific capacitance value (1470 F/g) than that of PAA/CoFe2O4 NCs (572 F/g) and CoFe2O4 (214 F/g) NPs at a current density of 1 A/g which is due to the synergistic effect of g-C3N4 assisted PAA on CoFe2O4. Hence, it can be concluded that the resulting g-C3N4/PAA/CoFe2O4 NCs will deliver an excellent catalytic and electrochemical performance and hence we believe that our findings provide a new platform for efficient photocatalytic and supercapacitor applications.

Effect of Firing Temperatures on Phase Formation, Microstructure, Dielectric and Magnetic Properties of Ni0.6Zn0.4Fe2O4 Ceramics Synthesized by the Solid-State Combustion Technique

In this study, the effect of firing temperatures on phase formation, microstructure dielectric and magnetic properties of Ni0.6Zn0.4Fe2O4 (NZFO) ceramics were investigated. The NZFO powder were synthesized by the solid-state combustion technique using glycine as a fuel to reduce the reaction temperature. All samples were calcined in the range of 900 °C–1100 °C for 2 h and sintered in the range of 1175 °C–1275 °C for 2 h. A pure ferrite phase was found in the powders calcined above 1000 °C and the average particle size of NZFO powders was increased from 0.39 µm to 0.59 µm when the calcination temperature was increased. The x-ray diffraction (XRD) analysis results confirmed the formation of pure spinel structure with cubic phase in all the ceramic samples. The average grain size (5.54–2.80 µm) was slightly decreased, and the dielectric constant (239–13) tended to decrease with increasing sintering temperature. As the sintering temperature increased to 1250 °C, it was found that the lattice parameters (8.366–8.387 Å), the density (5.29–5.35 g/cm3), and saturation magnetization (81.51–93.92 emu/g) tended to increase after that decrease.

Efficiency of nanostructured CuxCo3-xO4 and NixCu1-xCo2O4 electrodes as electrocatalysts for the oxygen evolution reaction–revisited

Binary and ternary cobalt-based spinel oxides have been shown to possess enhanced electrocatalytic activity and stability towards the oxygen evolution reaction (OER), however their performance is inconsistent. In this work, copper and nickel-copper substituted cobalt spinel oxides, CuxCo3-xO4 (x = 0, 0.25, 0.5, 0.75 and 1) and NixCu1-xCo2O4 (x = 0.25, 0.5, 0.75, 0.9 and 1), were prepared by the thermal decomposition method to re-examine their properties. We used several physical and chemical characterization methods to understand their behavior. The formation of spinel structure was confirmed by X-ray diffraction analysis, however, CuxCo3-xO4 remains monophasic only up to x = 0.75. CuCo2O4 was found to contain an additional CuO phase. The lattice parameters were determined as a function of the composition and found to increase with increased Cu and Ni content in the cobalt spinel lattice, which supports Cu and Ni incorporation in the spinel structure. For CuxCo3-xO4 electrodes, the lattice parameter gradually increased when cobalt is replaced by copper in the composition. NixCu1-xCo2O4 lattice parameters are higher than those of CuxCo3-xO4 but do not display a particular trend with replacement of Cu by Ni. The XPS analysis indicates the existence of various chemical species on the surface of the electrodes with a significant amount of NiO being detected on the surface of Ni-containing samples. The core-level spectra of all metal cations indicate the presence of mixed-valence states in the spinel structure. The roughness factor was determined by measuring the double layer capacitance of the electrodes using cyclic voltammetry and the data obtained was verified by performing electrochemical impedance spectroscopy (EIS) in a region of low faradaic current. The incorporation of Cu and Ni significantly increased the surface area of cobalt oxide. The current density obtained from cyclic voltammetry (CV) data is reported as a function of the geometric and the real surface areas for each sample, which revealed that Co3O4 possesses the highest current density than other Cu or Cu and Ni-containing cobalt spinel oxides towards OER when corrected for differences in surface area. However, the addition of Cu could be viewed as beneficial as it provides a lower onset potential for OER and results in a relatively high current density compared to Co3O4. NixCu1-xCo2O4 materials have a similar current density per unit geometric area, however, when corrected for real surface area these electrodes display lower catalytic activity for OER than CuxCo3-xO4 (x = 0 to 1). The presence of a significant surface NiO species may have affected the catalytic activity of Ni-containing samples. The data will be discussed in the context of variable material performance found in the literature.

Magneto-Optical Properties of Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 Nano Ferrite for Application of Soft Magnetic Material

Abstract: Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 spinel ferrite powder is successfully synthesized using sol-gel auto combustion technique. The structural, optical and magnetic properties investigated by using X-ray Diffractometer, FTIR Spectrometer, Scanning Electron Microscope and Vibrating Sample Magnetometer (VSM). XRD analysis confirmed that formation of Nano crystalline cubic spinel structure of the sample. The crystallite size of synthesized nanoparticles is about 29.45nm. The IR study support the confirmation spinel structure of Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 sample. Band gap energy Eg obtained using UV-Visible absorption data is about 2.4238 eV. The magnetic properties have been studied from VSM data shows that

Green synthesis of cobalt ferrite and Mn doped cobalt ferrite nanoparticles: Anticancer, antidiabetic and antibacterial studies

CoFe2O4 are important magnetic NPs with high coercivity and moderate magnetization.These properties of CoFe2O4 NPs show variation when doped with various metals. Recent studies explained that Cobalt ferrites doped with metal ion like Mn+2, have attracted increasing attention in many applications, particularly in biomedical applications. A relatively simple way is employing plants and their extracts as precursors instead of toxic chemicals to produce NPs with desirable characteristic. In current study we report green synthesis and characterization of magnetic (CoFe2O4, MnCoFe2O4, CoFe2O4@S.C, MnCoFe2O4@S.C) nanoparticles using ethanolic extract of Swertia Chirata. To enhance application as biocompatible magnetic nano drug delivery vector and cell targeting efficacy of drugs, Glimepiride (GLM), Dexamethasone (DXM), Fexofenadine (FEX) and Levofloxacin (LVX) 1were loaded on synthesized NPs.Synthesized CFNPs has been broadly characterized and applied for in vitro anticancer, antidiabetic and antibacterial potential. For synthesis of CoFe2O4 (CF), CoMnFe2O4 (CFM), CoFe2O4@S.C (SCF) & CoMnFe2O4 @S.C (SCFM), stochiometric amounts 5mmol of CoCl2·6H2O (0.284g) and 10mmol FeCl3·6H2O (0.378g) were dissolved in 13mL of deionized water. To this sodium acetate (3.05g) and urea (0.6g) were added until complete dissolution. Afterward n-heptane was added, and contents were then transferred to Teflon lining autoclave at 180°C for 4h. Black powder CoFe2O4 NPs after washing, were dried and calcined at 450oC for 2h. XRD diffractogram of CF have proved the single-phase cubic spinel structure formation for all samples. Swertia Chirata formulations were shown to have effective in vitro antidiabetic activity. CF, CFM & SCFM showed good inhibition of α-glucosidase with very low concentration 6µg/mL, 5µg/mL and 4µg/mL as compare to 12.41µg/mL of acarbose. SCF showed that the value slightly higher than 16µg/mL compared to standard. Drug loaded CFNPs (L-CFNPs, F-CFNPs, D-CFNPs & G-CFNPs) also effectively inhibited α-glucosidase. IC50 value for CFNPs inhibition of α-glucosidase was 12.4µg/mL.All synthesized CF NPs showed cytotoxic potential against breast cancer cells MCF-7. About 50-60% cell viability and cytotoxicity 40% were observed for bare CFNPs as compare to Doxorubicin with related toxicity 80% and 20% cell viability.Among synthesized samples almost all samples without conjugation of any drug showed activities against at least one bacterial strain. CFM, SCF, SCFM were active against S. aureus at concentration 100µg/mL, 100µg/mL, and 50µg/mL respectively. The synthesized CF NPs showed significant cytotoxic potential against MCF-7 breast cancer cell line. Further, drug loaded samples displayed lesser cell viability and slightly increased cytotoxicity in range of 40-50% in comparison with bare CFNPs. However, higher toxicity was observed for CFMGS towards MCF-7 cells with results nearly equal to Doxorubicin with significant decrease in viability.CF, CFM & SCFM showed good inhibition of α-glucosidase with very low concentration 6µg/mL, 5µg/mL and 4µg/mL as compare to 12.41µg/mL of acarbose.Among synthesized samples almost all samples without conjugation of any drug showed activities against at least one bacterial strain.

Investigation of Cr3+ doped Zn-Co nanoferrites as potential candidate for self-regulated magnetic hyperthermia applications

Controlling the Curie temperature (TC) in the range from 42 °C–46 °C in magnetic hyperthermia (MH) therapy is an essential research topic because overheating can cause irreversible damage to healthy tissue. When TC is in the above temperature range, the magnetic nanoparticles reach a paramagnetic state, effectively turning off the MH treatment. In this work, we synthesized Zn-Co nanoparticles of representative composition Zn0.54Co0.46CrxFe2-xO4, where the Fe3+ cations are carefully replaced by Cr3+ ions, which allow a precise tuning of TC and hence the self-regulation of MH. The x-ray diffraction analysis of the prepared nanoparticles confirms the formation of a single-phase cubic spinel structure. The average crystallite of the nanoparticles increases with Cr3+ doping, while the Tc and saturation magnetization decrease considerably from 78 °C (x = 0.1) to 27 °C (x = 0.6) and 46.6 emu g−1 (x = 0.1) to 15.3 emu g−1 (x = 0.6), respectively. Besides MH potential of the investigated samples as revealed from specific absorption rate (SAR) assays and the maximum temperature reach (Tmax), vary from 7 W g−1 and 37.3 °C, for x = 0.6, to 38 W g−1 and 62.9 °C, for x = 0.1, we found that the composition Zn0.54Co0.46Cr0.4Fe1.6O4 is more promising with SAR of 22 W g−1 and Tmax = 42.3 °C, which is precisely lies in the safe temperature range to automatically activate the self-regulation during the magnetic hyperthermia treatment. The results reveal an excellent combination between size distribution and Cr3+ content in Zn-Co-based ferrite, which has a great potential for self-regulated magnetic hyperthermia applications.

Synthesis and investigation of structural, elastic, and electrical properties of cobalt and magnesium substituted Ni–Zn spinel ferrite nanoparticles

The sol–gel auto-combustion approach was used to create Ni0.4M0.2Zn0.4Fe2O4 (M = Ni2+, Mg2+, and Co2+) nanoparticles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy (EDS), and an inductance–capacitance–resistance (LCR) meter were used to analyse the samples’ structural, elastic, and electrical properties. In all samples, the XRD patterns obtained indicated the formation of a monophasic cubic spinel structure with no identifiable impurity phase, which was supported by EDS investigations. The introduction of substituting ions, specifically Mg2+ and Co2+, into Ni–Zn ferrite nanoparticles results in an increase in the lattice parameter. The lattice parameter for Ni–Zn is 8.377 Å, while for the substituted nanoparticles it is 8.389 and 8.388 Å for Mg2+ and Co2+ respectively. Additionally, the crystallite size of the substituted nanoparticles increases to 46.57 nm from 40.75 nm for Ni–Zn. However, the x-ray density of the substituted nanoparticles decreases to 5.180 and 5.337 g cm−3 for Mg2+ and Co2+ respectively, from 5.358 g cm−3 for Ni–Zn. The elastic parameters, such as the Young’s modulus, Debye temperature, bulk modulus, and rigidity modulus, were calculated. The good elastic characteristics of Ni–Zn ferrite were confirmed and may be explained by the lower lattice parameter values and smaller crystallite sizes. Temperature and frequency effects on dielectric behaviour and AC electrical conductivity (σ AC) were investigated. At ambient temperature, the dielectric characteristics, specifically the dielectric constant (ϵ′) and loss tangent (tanδ), were computed over a frequency range of 100–2 MHz. The compositions display normal dielectric properties, which are attributed to the interfacial polarisation following the Maxwell–Wagner model. The AC conductivity of nanoparticles was shown to decrease when Mg2+ and Co2+ were substituted into Ni–Zn ferrite. Furthermore, the AC conductivity diminishes with decreasing frequency, which is a sign of ionic conductivity. There was a direct relationship between the temperature and the values of ϵ′, tanδ, and σ AC for different ions.

Feasibility of superparamagnetic NiFe2O4 and GO-NiFe2O4 nanoparticles for magnetic hyperthermia

Superparamagnetic Ni-ferrite and their composite with graphene oxide nanoparticles are synthesized using simple hydrothermal method. The morphology and the crystal structure measurements show formation of spinel structure with cubic/octahedral shape nanoparticles with average particles size of 16.63 nm and 12.87 nm for NiFe2O4 and GO-NiFe2O4 respectively. The magnetic properties show superparamagnetic behavior at room temperature with saturation magnetization of 50 and 35 emu/g and Coercivity of 35 and 25 Oe for NiFe2O4 and GO-NiFe2O4 respectively. The zero-field cooling and field cooling magnetization dependence on temperature measurements yield blocking temperature of 315 and 257 K for NiFe2O4 and GO-NiFe2O4 respectively. Those values confirm the superparamagnetic behavior of the samples. Moreover, the blocking temperature of the NiFe2O4 is within the therapeutic temperature range of magnetic hyperthermia therapy. The feasibility of hyperthermia reveals heating power of 165 and 15 W/g for NiFe2O4 and GO-NiFe2O4 respectively, which is comparable and even much better than the previous published work by others. Therefore, the findings open new route for the potential of NiFe2O4 and GO-NiFe2O4 nanoparticles for hyperthermia and to be tested for in vitro/ in vivo hyperthermia in the future.

Carbonaceous MnFe2O4 nano-adsorbent: Synthesis, characterisation and investigations on chromium (VI) ions removal efficiency from aqueous solution

Carbonaceous manganese ferrite nanoparticles were prepared at relatively lower temperature using co-precipitation method followed by a single-step pyrolysis process. Synthesized nanoparticles were further characterized by different spectroscopic and microscopic techniques. The X-ray Diffraction (XRD) study confirmed the formation of single phase cubic spinel structure and the presence of graphitic carbon of plane (002) and the size of the prepared nanostructure was of 36 nm. With the confirmation of formation of carbonaceous MnFe2O4 and the number of oxygen functionalities such as hydroxyl and C-O-C groups emanating from the carbon matrix, as confirmed by the Fourier Transform Infrared (FT-IR) studies motivated their usage to remove Cr (VI) ions from aqueous solution. The study parameters such as influence of time, adsorbent dosage, concentration and pH are explored along with isotherm and kinetic studies. The carbonaceous nanoparticle was able to remove Cr (VI) by ∼80% at native pH, with a carbonaceous MnFe2O4 dose of 10 mg, and the initial concentration 10 ppm of contaminant with the contact time, 80 min and is found promising for the practical applications.

Structural, magnetic, and antibacterial activity of the pure, Zn-doped, and Zn-doped/sugar-assisted coprecipitation synthesized semicrystalline Co3O4 compound

Undoped, Zn-doped, and Zn-doped/sugar-assisted semi-crystalline structures of Co3O4 were made by introducing a facile precipitation approach. The synthesized compounds were tested for surface characteristics, magnetic properties, and antibacterial activity. Powder X-ray diffraction (XRD) analysis confirmed semi-crystalline behavior and spinel structure formation in all synthesized compounds. Using scanning electron microscopy (SEM) characterization, microstructure formation along with the large agglomeration of spherical particles, uniform distribution of spherical particles, and spherical-flake-like particle structures were noticed for the pure, Zn-doped, and Zn-doped/sugar-assisted Co3O4 samples, respectively. From the vibration sample magnetometry (VSM), Zn-doped/sugar-assisted Co3O4 was found to have relatively lower saturation magnetization when compared to pure Co3O4 and Zn-doped Co3O4 material. The antibacterial performance of the synthesized compounds against the bacteria Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus) has been tested. The above-mentioned germicidal responses showed a relatively larger inhibition zone for the Zn-doped and Zn-doped/sugar-assisted Co3O4 compared to the undoped Co3O4 sample. The obtained diameter inhibition zone values of all synthesised compounds are comparable to the standard positive and negative control.

Ni-doped Mg-Zn nano-ferrites: Fabrication, characterization, and visible-light-driven photocatalytic degradation of model textile dyes

Novel Ni2+-doped NixMg0.5Zn0.5-xFe2O4 [x = 0.0 to 0.5] nano-ferrites have been successfully prepared by the facile co-precipitation method. The XRD data demonstrated the formation of a single-phase cubic spinel structure. The optical band gap of the synthesized samples was found to increase with increasing Ni2+ content from 1.72 eV (x = 0.1) to 1.82 eV (x = 0.5). Samples with Ni2+ doping exhibit a transition from superparamagnetic to soft ferromagnetic activity. Ni0.5Mg0.5Fe2O4 catalyst has been found to have enhanced degrading efficiencies of 95.92 and 90.21% against methylene blue and xylenol orange in visible light, respectively. The main reactive species, as determined by scavenging activity, were hydroxyl radicals.

Effect on magnetic behaviour of Ag and Cd doped cobalt ferrite nanoparticles prepared by glycine-assisted sol-gel auto combustion method

The nanocomposites of the Silver (Ag) and cadmium (Cd) based, cobalt ferrite having formula AgxCdxCo1–2xFe2O4 (where x = 0.0, 0.05, and 0.1) have been successfully prepared by glycine-assisted Sol-gel derived auto combustion technique. The synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), UV–visible spectrum, and Vibrating Sample Magnetometer (VSM). The XRD and FTIR results reveal the formation of a single-phase cubic spinel structure with crystallite sizes 14–19 nm. SEM analysis of surface morphology revealed spherical and cubic-shaped nano-particles. FTIR spectra indicated two fundamental absorption peaks around 580 cm-1 and 460 cm−1. This confirmed the existence of m-o bonding in the synthesized products corresponding to the stretching vibration of tetrahedral (A) and octahedral (B) lattice sites. According to UV-Visible analysis, it is observed that the optical band gap energies vary from 1.88 eV to 1.52 eV as the Ag/Cd concentration increased. From VSM data, the magnetic behavior of prepared specimens is studied and the corresponding variations in the (Ms), (Hc), (Mr), and Mr/Ms values are analyzed. This prepared composites materials are recommended for magnetic storage applications.

Structural and optical properties of gadolinium doped-magnetite nano-crystal for photocatalytic application

Doped ferrite materials offer a combination of enhanced magnetic properties, multifunctionality, higher Curie temperature, biocompatibility, and potential energy applications. Their unique characteristics make them appealing for research in diverse fields, including materials science, electronics, biomedical engineering, and energy technology. In present work, Gadolinium-doped magnetite samples are synthesized following the co-precipitation method. The effects of doping on the structural and optical properties of Fe3O4 are studied. Structural parameters of the samples such as cell parameters, cell volume crystalline size, x-ray density, and average micro-strain are calculated from the analysis of x-ray diffraction (XRD) data via Rietveld refinement method. An increase in crystalline size and cell volume is observed while a reduction in micro-strain is observed with increase in doping concentration. The particle size estimated from FE-SEM data ranges from 9 to 16 nm and is in good agreement with XRD data and confirms the formation of nanoscopic phase of the particles. The presence of characteristic peaks concerned with tetrahedral and octahedral site vibrations in the Fourier transform infrared spectroscopy data approve the formation of inverse spinel structure. The distribution of Gd in the samples is determined with Energy dispersive x-ray analysis. The optical studies show that the direct and indirect band gaps decrease from 4.07 to 3.95 eV and 3.79–3.65 eV, respectively. These values of band gap are indicated the potential use of the synthesized nanoparticles for photocatalytic application.

Complex dielectric-impedance spectroscopic studies of magnetite added chitin biopolymer

We have successfully synthesized magnetic chitin (MCH) by incorporating iron oxide nanoparticles into biodegradable and abundantly naturally available chitin by the coprecipitation method. X-ray diffraction (XRD) characterization revealed formation of cubic inverse spinel structure of Fe3O4 nanoparticles. In addition to this, other characterization studies like energy dispersive X-ray analysis (EDX) and vibrating sample magnetometry (VSM) were also performed to have an insight into the compositional and functional nature of the structure. A detailed spectroscopic study of complex impedance and dielectric constant for a wide frequency range of ~1 Hz to 10 MHz at discrete temperatures ~300–400 K has been performed by us for the first time on MCH in order to understand various relaxation processes. From permittivity, we have estimated the height of the potential barrier to be ~95.8 ± 0.3 meV. Impedance measurements yielded an activation energy of ~35.85 meV. Thermogravimetric analysis (TGA) of the sample showed exceptionally high thermal stability of the sample with percentage of residual mass at 800 ℃ being ~73% in MCH, which is quite high in comparison to the pristine chitin. An S shaped curve obtained through VSM measurement confirmed the superparamagnetic nature of the nanocomposite. The study assumes significance in the present scenario of rising awareness about the environment and demand to explore alternative green materials with numerous biomedical/environmental applications ranging from drug delivery vehicles in COVID-19 treatment to food packaging.

Structural, Frequency and Temperature Dependent Dielectric Properties of Zn2+ Substituted Ni-Co Based Spinel Ferrite (ZnxNi0.8−xCo0.2Fe2O4)

Zinc substituted nickel-cobalt ferrites, i.e., ZnxNi0.8−xCo0.2Fe2O4 (x = 0.0, 0.05, 0.10 and 0.20) with average crystallite size 100 nm were synthesized by citrate-gel auto-combustion method to investigate effects of Zn2+ substitution on the structural and dielectric properties. Both X-ray diffraction (XRD) and IR spectroscopy studies confirms the formation of pure cubic spinel structure. Variation of lattice parameter infers Vegard’s law linear dependence with the addition of Zn2+ concentration. The temperature-dependent behavior of dielectric and modulus spectra has been studied within the frequency range 100 Hz-100 kHz for different temperatures between 100 K and 400 K. It was concluded that the dielectric responses of ZnxNi0.8−xCo0.2Fe2O4 are found to be frequency dependent and thermally activated. Also, In the Zn doped ferrites variations of dielectric loss (tan δ) and the imaginary part of electric modulus (M") show the presence of the non-Debye type of dielectric relaxation. Rise in Zinc concentration leads to a decrease in dielectric constant (ε r) due to the declining of Fe3+–O–M2+ conducting network (M is Co or Ni). Here, we report a low loss tangent factor of the order of for the sample Ni0.6Zn0.2Co0.2Fe2O4 make this composition suitable for high frequency-applications at room temperature. The activation energy is calculated from electric modulus formalism and DC electrical conductivity and found to increase with further substitution of Zn2+ concentration.

Enhanced Electrochemical Performance of Rare-Earth Metal-Ion-Doped Nanocrystalline Li4Ti5O12Electrodes in High-Power Li-Ion Batteries

A comprehensive and comparative exploration research performed, aiming to elucidate the fundamental mechanisms of rare-earth (RE) metal-ion doping into Li4Ti5O12 (LTO), reveals the enhanced electrochemical performance of the nanocrystalline RE-LTO electrodes in high-power Li-ion batteries. Pristi ne Li4Ti5O12 (LTO) and rare-earth metal-doped Li4-x/3Ti5-2x/3LnxO12 (RE-LTO with RE = Dy, Ce, Nd, Sm, and Eu; x ≈ 0.1) nanocrystalline anode materials were synthesized using a simple mechanochemical method and subsequent calcination at 850 °C. The X-ray diffraction (XRD) patterns of pristine and RE-LTO samples exhibit predominant (111) orientation along with other characteristic peaks corresponding to cubic spinel lattice. No evidence of RE-doping-induced changes was seen in the crystal structure and phase. The average crystallite size for pristine and RE-LTO samples varies in the range of 50-40 nm, confirming the formation of nanoscale crystalline materials and revealing the good efficiency of the ball-milling-assisted process adopted to synthesize nanoscale particles. Raman spectroscopic analyses of the chemical bonding indicate and further validate the phase structural quality in addition to corroborating with XRD data for the cubic spinel structure formation. Transmission electron microscopy (TEM) reveals that both pristine and RE-LTO particles have a similar cubic shape, but RE-LTO particles are better interconnected, which provide a high specific surface area for enhanced Li+-ion storage. The detailed electrochemical characterization confirms that the RE-LTO electrodes constitute promising anode materials for high-power Li-ion batteries. The RE-LTO electrodes deliver better discharge capacities (in the range of 172-198 mAh g-1 at 1C rate) than virgin LTO (168 mAh g-1). Among them, Eu-LTO provides the best discharge capacity of 198 mAh g-1 at a 1C rate. When cycled at a high current rate of 50C, all RE-LTO electrodes show nearly 70% of their initial discharge capacities, resulting in higher rate capability than virgin LTO (63%). The results discussed in this work unfold the fundamental mechanisms of RE doping into LTO and demonstrate the enhanced electrochemical performance derived via chemical composition tailoring in RE-LTO compounds for application in high-power Li-ion batteries.