Sol-gel Auto-combustion Route Research Articles

Synthesis, characterization, DFT calculations, and anticancer properties of VI-period and f-block elements-substituted zinc oxide nanopowders

Nanotechnology provides promising ways in which a wide range of new materials can be manufactured which appear to have enormous potential in the field of biomedicine and life sciences. ZnO can be applied in many physical and optical processes and used as a good anti-cancer agent. ZnO NPs are recognized as SAFE or GRAS, non-toxic and biocompatible particles. In this study, wurtzite ZnO samples co-doped by rare earth elements (Tb, Er) were prepared via sol-gel auto-combustion route and their crystallographic structure as well as their morphologies were examined using XRD and TEM techniques. The analysis disclosed that all synthesized products crystallized in a hexagonal structure and the crystallites/particles size diminished with the increase of co-doping content. The electronic structure and optical properties of the different products were assessed using DFT calculations. Doping Tb and Er rare earth elements into ZnO has a significant effect on its optoelectronic properties. The computational study showed that the co-doping of Tb and Er on pure ZnO decreased the band gap and increased the refractive index. The extinction spectrum of pristine ZnO showed a peak in the ultraviolet region at 5 eV, while those of the co-doped ZnO samples displayed stronger peaks in the infrared region (near 0.4 eV). The anticancer properties of Tb/Er co-doped ZnO nanoparticles were examined on cervical cancer (HeLa cells) and colon cancer (HCT-116) by using an in vitro MTT assay. The cell viability assay findings indicated a reduction in HeLa and HCT-116 cells after 48 hours of treatment of the synthesized samples. The treatment with co-doped ZnO nanoparticles produced chromatin condensation and formation of apoptotic bodies in HCT-166 cells, which indicates that the prepared co-doped ZnO nanoparticles induced programmed cell death in HCT-116 cells. According to these results, it can be concluded that the prepared Tb/Er co-doped ZnO nanoparticles have promising applications in developing new optoelectronic devices and also in treating cervical and colon cancers.

Influence of bismuth and cobalt doping on structural, dielectric, and magnetic properties of M-type calcium hexagonal ferrites

M-type hexagonal ferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized M-type hexagonal ferrites is still a big challenge. Herein the fabrication of M-type hexaferrite with nominal composition Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with high quality is reported by the sol-gel auto combustion route. The objective of the study is to improve the structural, spectral, dielectric, and magnetic characteristics of M-type hexagonal ferrite which was achieved through the variation of concentration of Cobalt and Bismuth. X-ray diffraction (XRD) patterns confirmed the single-phase M-type hexagonal structure. The crystallite size of all samples was found to be in the range of 42–49 nm. Other parameters such as lattice parameters a & c, unit cell volume, crystallite size, X-ray density, Bulk density, and porosity were also calculated. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metal-oxygen stretching vibrations that confirmed the formation of hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure and homogeneously distributed grains were examined. The dielectric constant was high at low frequency and then decreased with increasing frequency, while the dielectric loss was decreased appreciably with doping. The saturation magnetization ranged from 15.51 to 38.27 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was found to be in the range of 0.19–0.78. The dielectric and magnetic properties of Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with the variation of Co and Bi revealed that these materials are good candidates for modern devices.

Advancements in multiferroic, dielectric, and impedance properties of copper–yttrium co-doped cobalt ferrite for hydroelectric cell applications

This paper explores yttrium and copper co-doped cobalt ferrite [Co1−x Cu x Fe1.85Y0.15O4] synthesized via the sol–gel auto-combustion route (0.0 ⩽ x ⩽ 0.08). Investigating the impact of co-dopants on CoFe2O4, the study reveals altered cation distribution affecting the structure, multiferroic, and electrical properties. X-ray diffraction studies show nanocrystalline co-doped cobalt ferrites with lattice expansion and smaller grains due to Cu–Y co-doping. Fourier transform infrared spectroscopy confirms inverse spinel family classification with tetrahedral lattice shrinkage. Field emission scanning electron microscopy indicates a grain size of approximately 0.12 μm. Ferroelectric analysis reveals a peak saturation polarization of 23.42 μC cm−2 for 8% copper doping, attributed to increased Fe3+ ions at tetrahedral sites. Saturation magnetization peaks at 54.4706 emu g−1 for 2% Cu2+ ion substitution [Co0.98Cu0.02Fe1.85Y0.15O4] and decreases to 37.09 emu g−1 for 4% Cu substitution due to irregular iron atom distribution at tetrahedral sites. Dielectric studies uncover Maxwell–Wagner polarization and high resistance in grain and grain boundaries using impedance spectroscopy. Fabricated hydroelectric cells exhibit improved ionic diffusion, suggesting their use in potential hydroelectric cell applications.

Microstructural, morphological and magnetic behaviour of Al3+ replaced BaFe11.5Co0.5O19 hexaferrites synthesized via sol-gel auto combustion route

In this work, polycrystalline BaFe11.5-xAlxCo0.5O19 (0≤x≤2) hexaferrite samples were synthesised by means of the sol–gel technique. Thereafter, the magnetic and structural properties are thoroughly examined. Cell refinement and XRD examination verified a magnetoplumbite hexaferrite arrangement with a space group of P63/mmc for each sample. The parameters ‘a’ and ‘c’ in the lattice fall in value from 5.885 Å to 5.875 Å and from 23.117 Å to 23.049 Å, respectively. Both the average crystallite size and the unit cell volume exhibit a declining trend as the doping level increases. For M-type hexaferrites, the optimal range of c/a values is determined to be 3.923–3.928. X-ray density (dx) and bulk density (db) decline with rising doping contents until x=1.5 doping content, at which point they exhibit an increasing trend. The results showed that as the doping amount increased, the saturation and remanence magnetizations decreased. Coercivity and magnetocrystalline anisotropy are rising together. Both the anisotropy field (Ha) and the anisotropy parameter (B) exhibit a rising trend with doping content. Coercivity of 5.896 kOe, anisotropic applied field of 1.84 kOe, saturation magnetization of 42.68 emu g−1, remanence magnetization of 24.414 (emu/g), and magnetic moment per formula unit-(mB) of 11.19 μ B are the best magnetic properties obtained for the BaFe10Al1.5Co0.5O19 sample.

Structural, physicochemical and electrical properties of Co2Y-type barium hexaferrites

Y-type hexaferrite ceramic materials of nominal composition Ba2Co2CrxYxFe12-2xO22 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were synthesized by sol-gel auto combustion route. Y-type hexaferrites are technologically important ceramic materials for fabricating modern electronic devices and microwave absorbers due to their unique electrical and dielectric properties and reflection loss behavior. XRD classifies the single-phase formations with space group R m. The crystallite size of the synthesized samples was calculated in (34–41) nm range. The specific absorption band in FTIR spectra approves the (Fe–O) stretching vibrations at wavenumbers 446 and 478 cm−1. The substitution of iron by Cr3+ and Y3+ increases DC resistivity from 1.03 × 1011 to 1.17 × 1012 Ω cm by limiting the electrons jumping between ferrous and ferric ions. The activation energy and drift mobility were also calculated among the substituting content of Cr3+-Y3+. The dielectric response in 1 MHz–6 GHz frequency was determined and the effect of substitution has been observed. The Maxwell-Wagner (MW) bilayer model is used to study dispersion in dielectric parameters with reference to applied frequency. The maximum values of dielectric losses were obtained at 6 GHz in the range of 0.37–0.60. The coercivity values confirms the soft magnetic nature of synthesized samples. The microwave absorption (MW) properties of synthesized materials were improved upon Cr3+-Y3+ substitution. Minimum reflection loss RLmin = −66 dB (99.99% absorption of MW) at 1.46 GHz frequency and 1.96 mm thickness was obtained for x = 0.09 composition. All investigated samples are efficient materials for stealth technology, radar cross-reduction, EM interference shielding, and high-frequency applications.

Influence of Ni2+ ions on structural, spectral and dielectric properties of Sr–Co spinel ferrites synthesized by sol-gel auto-combustion route

Nickel substituted Sr–Co nano spinel ferrites with composition Sr0.5-xNixCo0.5Fe2O4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value.

Comparative Study of Rare Earth Nd and Sm Doping on the Structural, Morphological, Optical, Magnetic, and Electromagnetic Traits of Mg-Zn-Cu Spinel Nanoferrites

In the current study, the magnetic nanoparticles of neodymium and samarium substituted Mg-Zn-Cu, with a chemical composition of Mg0.5Zn0.5Cu0.05RxFe1.95-xO4 (x = 0.05; R = Nd, Sm) were produced via the sol-gel auto-combustion route. XRD indicates the evolution of a cubic symmetry having Fd3m space group and no impurities at the room temperature. The FESEM images show the irregularly shaped and agglomerated grains in all samples. FTIR examination reveals the stretching vibrations among the metal cations and anions at interstitial vacancies. The M-H graphs demonstrates that the prepared nanoferrites have low rentivity (0.18–0.84 emu g−1) and coercivity (11.25–34.03 Oe) indicating the formation of superparamagnetic nature. From the electromagnetic traits, the observed sample’s real magnetic permeability (μ″) and permittivity (ε′) along with dielectric loss and magnetic loss reduced with increasing applied field frequency, indicating the typical behaviour of spinel nanoferrites. This may be explained by Maxwell-Wagner interfacial polarisation and the electron hopping among the ferrous and ferric ions. The variations in coercivity, anisotropy constant, and electromagnetic traits provide strong evidence that all of the samples are thermally stable and have the potential to be used in solenoids and transformers, and also, in the more resistive devices that operate at the high frequency.

GO optimization strategies for improved capacity retention in transition metal oxides based ternary nanocomposites for high-performance supercapacitors

This work presents the optimization of GO in transition metal oxide based ternary nanocomposites (NiO/ZnO@(GO)x)for electrode materials in supercapacitor applications. The nanocomposites were synthesized using a straightforward sol-gel auto combustion route followed by sonication. It was observed from XRD analysis that crystallite sizes of NiO/ZnO@(GO)x nanocomposites vary between 49 and 24 nm. According to morphological study, the TEM images depict a hybrid nanoarchitecture with NiO/ZnO nanoparticles dispersed on graphene sheets. The maximum specific capacitance of 1833.9Fg−1 was obtained for NZG3 (NiO/ZnO with 6% GO).Furthermore, largest capacity retention of 98.7% was achieved for NZG3 after 6000 continuous cycles. NZ demonstrated 96% capacitance retention, for NZG1 it was 97.2% and capacity retention for NZG3, it was 98.7%. Therefore,optimized concentration of GO in NiO/ZnOnancomposite to achieve maximum specific capacitance and cyclic stability was found to be forNZG3 nanocomposite. The Rs values attained were found to be 6.7 Ω, 5.8 Ω, 5.4 Ω, 4.4 Ω and 4.9 Ω for NZ, NZG1, NZG2, NZG3 and NZG4 respectively whereas Rctvalues for NZ and NZG electrodes i.e. NZG1, NZG2, NZG3 and NZG4 10.0 Ω, 9.4 Ω,8.5 Ω,7.8 Ω and 8.1 Ω respectively, demonstrating that GO plays an important role in enhancing conductivity.

Dielectric and magnetic response of Cu-Co-Sm ferrite impregnated with graphene nanoplatelets for high-frequency device applications

This work studied a composite of graphene nanoplatelets (GNPs) impregnated copper-cobalt-samarium ferrites Cu0.5Co0.5Fe1.97Sm0.03O4/GNPs synthesized via sol-gel auto-combustion route. The structural, electrical, dielectric, and optical properties of the as-prepared composites were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), EDX, I-V characteristics, impedance measurement, raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) analysis, and UV–visible spectroscopy. XRD confirmed that the spinel ferrites had a crystalline single-phase FCC structure with the lattice constant of around 8.33 Å, and the crystallite size range from 54.10 nm to 51.85 nm. SEM analysis confirmed the homogenous dispersion of spinel ferrites in graphene sheets, and EDX confirmed the presence of all elements in ferrite composites with GNPs. Furthermore, the spinel matrix was confirmed by the Raman and UV-visible analysis. A minimum particle size of 21.73 nm was determined using TEM, and the minimum value of activation energy (0.01 eV) was obtained from IV characteristics for ferrite composite with 2.5% GNPs. Further, our ferrite composites with GNPs demonstrated improved electroconductive properties, with conductivity ranging from 5.88×10−8S/cm to 1.04×10−6S/cm at 673 K. The real & imaginary part of permittivity, dielectric constant (ε’), and impedance (Z) were also improved with the addition of GNPs. At low frequencies, a permeability loss value of 0.81 was obtained for the ferrite composite with 5% GNPs. VSM analysis confirmed that the saturation magnetization decreased in ferrite composites with graphene nanoplatelets. The minimum value of skin depth of 1.03 mm was observed at 1.25 % GNPs. Our ferrite composites with GNPs exhibited minimal eddy current at high frequencies, making them promising candidates for high-frequency device applications.

Structural, morphological, dielectric, and spectral properties of Sr-Mg-Ho X-type magnetic nano materials suitable for microwave absorption application

Holmium (Ho3+) substituted Sr2Mg2Fe28O46 X-type hexa-ferrites were synthesized using the sol-gel auto-combustion route. The single phase of Sr2Mg2Fe28-xHoxO46 where 0.00 ≤ x ≤ 0.20, Δx = 0.05, X-type hexa-ferrites was confirmed using XRD peaks. The crystalline size was studied from XRD data and found to be in the 11 nm–24 nm range. The micro strain increased with the substitution of Ho3+. FTIR exposed the specific stretching vibration and absorption peaks in the 400 cm−1 - 600 cm−1 range. The force constant (ko) decreased from 1.74 N/cm to 1.65 N/cm with the increasing concentration of Ho3+. The grain size range is 371–493 nm, measured by SEM analysis, and plate-like structure plays a crucial role in enhancing the permeability of magnetic material. Transmission electron microscopy (TEM) analysis showed the hexagonal structure of X-type ferrites (x = 0.20). The results of the X-ray photoelectron spectroscopy (XPS) experiment confirmed the presence of all metal ions in the given composition with their required valences. The dielectric constant, dielectric loss, and tangent loss are found to increase with the substitution of the Ho3+ ion. In addition, the higher values of dielectric parameters and dielectric loss suggest that the material may suitable for high-frequency applications and best for microwave absorbers. Our aim is to discuss the characteristics and applications of microwave absorption materials, understand their behavior, and contribute to the development of upcoming novel devices. The resonance peak's appearance shows that these materials are best for multilayer chip inductors and EMI attenuation.

Impact of samarium on structural and dielectric properties of U-type hexaferrites synthesized by a sol-gel auto combustion route: Analysis of XPS, Raman and FTIR spectra

In this work, the impact of rare earth element samarium "Sm" substitution on Ba4Co2SmxFe36-xO60 U-type hexaferrites was studied in detail. Five compositions with step size x = 0.00, 0.025, 0.050, 0.075 and 0.1 were synthesized. These five series were prepared using the sol-gel auto-combustion method and the samples were sintered for 6 h at 1250 °C. The synthesized samples were characterized by XRD, FTIR, Raman Spectroscopy, X-ray photoelectron Spectroscopy and vector network analyzer (VNA). The structure crystallography of Ba4Co2SmxFe36-xO60 was examined via XRD. The impact of Sm3+ substitution was assessed across all lattice parameters. Lattice constants 'a' and 'c' were found between 5.886 and 5.881 Å and 113.179 to 113.037 Å, respectively. FTIR was used to learn more about the crystal structure and atomic vibrations between 400 and 1000 cm−1 wave number, where higher frequency bands appear at 570 cm−1 (tetrahedral site) and the lower frequency band occurred at 424 cm−1 due to the metal-oxygen stretching vibration (Fe-O) bond at the octahedral site. Each spectrum supported a U-type hexagonal structure i.e. an investigation of the chemical and intermolecular bonds via Raman spectra. XPS confirms the presence of elements in materials. Different dielectric parameters were observed in the 1 MHz to 6 GHz range of all prepared samples. Cole-Cole graphs of prepared materials highlighted the influence of grain boundaries. A solitary semicircle in the impedance of a specific section of grain boundaries was evidenced through Cole-Cole plots. Dielectric properties strongly depend on electron hopping between Fe2+ and Fe3+ ions. The optimized parameters suggest the utility of these materials in microwave devices, multilayer chip inductors and high-frequency electrical circuit applications to reduce skin effects.

Exploring the synergistic effects of La3+ substitution on dielectric performance of manganese cobalt ferrite: Implications for advanced electronic applications

La3+ substituted Mn0.5Co0.5Fe2O4 ferrites were synthesized through sol-gel auto-combustion route. The impacts of varying doping concentrations (0.03, 0.06 and 0.09) were studied on synthesized samples' structural, optical, morphological, vibrational, and dielectric properties. The spinel cubic phase of synthesized samples was confirmed by X-ray diffraction (XRD) analysis; increased La3+ concentration has altered the structural parameters of prepared ferrites. Diffuse Reflectance Spectroscopy (DRS) shows a decrease in band gap with increasing concentration of La3+. Morphology has been reviewed by Field Effect Scanning Electron Microscope (FE-SEM), and elemental composition was confirmed by Energy Dispersive X-ray (EDAX) spectra. In addition, M − O stretching bonds were verified employing Fourier Transform Infrared (FTIR) spectroscopy. Raman Spectroscopy shows five modes, further confirming the spinel structure. The XPS spectra verified the +2 oxidation state of Manganese. Finally, the dielectric constant, tangent loss, and AC (Alternating Current) conductivity were analyzed with temperature at several frequencies. The experimental results have unveiled intriguing findings: the dielectric constant exhibited its maximum value at the lowest frequency within the investigated range, and it demonstrated an increasing trend with the rising temperature at a specific frequency. Notably, introducing La3+ through substitution has led to a noteworthy enhancement in the dielectric constant, underscoring the novel impact of this dopant on the material's electrical properties. A positive correlation existed between AC conductivity and temperature; as the temperature increases, so does the AC conductivity. Also, it was found to be maximum at maximum frequency value for all samples. Additionally, it can be deduced that raising the La3+ concentration in crystal improves the dielectric characteristics of Manganese Cobalt ferrites.

Efficient photocatalysis of Zn1-2xEuxDyxO nanoparticles towards the degradation of hazardous Rhodamine B dye

Industrial waste is the principal source of highly toxic organic and heavy metals. Treating such effluence is highly required to provide a clean ecosystem for living organisms. Photocatalysis is one of the most efficient, economical, and time-efficient ways for the removal of industrial wastes. In the current search, we propose to prepare a series of Zn1-2xEuxDyxO samples (x = 0.00–0.05), using the simple sol-gel auto-combustion route. The XRD results indicated a hexagonal structure for all samples. The presence of europium and dysprosium elements and their successful doping into the ZnO were proved by XRD and EDX analyses. The mean crystallite size and the values of band gap energy were altered by the Eu and Dy doping. The photocatalytic action of Zn1-2xEuxDyxO samples was assessed for Rhodamine B degradation. The experiments indicated a degradation with an efficiency of 99.1%, 95.1%, and 97.4% for Zn0.98Eu0.01Dy0.01O, Zn0.94Eu0.03Dy0.03O, and Zn0.90Eu0.051Dy0.05O samples, respectively within 90 min. The Zn0.98Eu0.01Dy0.01O sample exhibited the maximum photocatalytic efficiency with an excellent rate constant (r = 0.054 min−1) among all samples. The obtained findings demonstrated that the Eu and Dy co-doping at a specific concentration is a useful way to reach an effective photocatalytic activity of ZnO nanoparticles.

Mg1-xNixGayFe2-yO4 nano catalysts for green hydrogen generation with highly efficient photo/electro catalytic water splitting applications

The production of nanomaterials for renewable energy as fossil fuel substitutes is anticipated as a viable solution to the pressing issues of environmental pollution and energy scarcity. We fixated on the development of Mg1-xNixGayFe2-yO4 (x = y = 0.0–0.03; steps: 0.01) nanocatalysts by sol-gel auto-combustion route (SGAC) for the hydrogen generation through overall photo and electrocatalytic water splitting. The spinel cubic phase with Fd3m space geometry was established from XRD results. FESEM images shows cubic and spherical formed grains with definite grain boundaries and grain size of 164 and 184 nm for the MgFe2O4 and Mg0.98Ni0.02Ga0.02Fe1.98O4 nanomaterials. Soft magnetic behavior with superior saturation magnetization (Ms) and moderate coercivity (Hc) of 2.72–29.24 emu/g and 51.23–257.86 Oe was obtained for all of the developed nanocatalysts. According to the research findings, Mg0.98Ni0.02Ga0.02Fe1.98O4 nanocatalyst shows the highest photocatalytic activity of 11.38 mmol gcat−1. The as-synthesised photocatalysts' repeatability and stability were evaluated throughout repeated runs of a 4-h reaction period conducted under identical circumstances. On the other hand, the electrocatalytic studies were carried via 3-electrode arrangement (i.e., working, counter and reference) in 0.5 M H2SO4 and 0.1 M KOH electrolytes for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). The overpotential for the MgFe2O4, Mg0.99Ni0.01Ga0.01Fe1.99O4, Mg0.98Ni0.02Ga0.02Fe1.98O4, and Mg0.97Ni0.03Ga0.03Fe1.97O4 electrocatalysts at 10 mA/cm2 were −0.866, −0.82, −1.02 and −0.92 V. Consequently, owing to these photocatalytic and electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient for hydrogen generation. However, MgFe2O4, and Mg0.99Ni0.01Ga0.01Fe1.99O4 nanomaterials show high zone of inhibition (ZOI) against Bacillus subtilis and Pseudomonas aeruginosa and therefore, making it valuable also for biological usages.

Photocatalytic and electrocatalytic hydrogen production promoted by Nd/La substituted cobalt–nickel magnetic nanomaterials

The current work concentrates on the design of Nd/La doped Co0.7Ni0.3Fe2O4 nanocatalysts for the green, clean, and sustainable generation of hydrogen through overall photocatalytic and electrocatalytic water splitting routes using sol-gel auto-combustion route. The spinel symmetry with a Fd3m geometry and cubic polycrystalline nature was observed for the developed catalysts. Spherical formed agglomerated nanoparticles having average grain size of 127.10 and 120.08 nm was confirmed for the produced Co0.7Ni0.3Fe2O4 and Co0.7Ni0.3Nd0.02La0.02Fe1.96O4 catalysts through the FESEM results. Maximum saturation magnetization (Ms) of 64.81 emu/g and coercivity (Hc) of 1234.54 Oe were attained by undoped Co0.7Ni0.3Fe2O4 catalyst. This shows the superior magnetic behaviour of our prepared catalysts, for magnetic recording applications. The estimation of photocatalytic hydrogen production for the prepared photo nanocatalysts was conducted under ambient conditions, with an irradiation from a UV-visible light having wavelength range of 200–2400 nm. The prepared Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 photocatalyst shows the maximum photocatalytic activity of 12.57 mmol gcat−1. Also, the photocatalytic hydrogen evolution, repeatability, and stability of all the prepared catalysts were analyzed at three successive cycles. The third cycle showed a little drop in photocatalytic hydrogen evolution to 11.26 mmol gcat−1 as compared to the first cycle. On the other hand, the electrocatalytic activity of produced electrocatalysts were determined towards the electrocatalytic HER via a three-electrode system in 0.5 M H2SO4 electrolyte. The produced Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 nanocatalyst shows excellent electrocatalytic HER activity as compared to other samples. Hence, with photocatalytic/electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient and suitable for the production of clean and green hydrogen energy sources.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.

Investigation on bio-synthesized Ni- and Al-doped cobalt ferrite using lemon juice as eco-fuel

Pure and doped cobalt ferrite (CoFe2O4) nanoparticles were prepared using sol-gel auto-combustion route with the aid of lemon juice as eco-fuel. In this study, Ni2+ and Al3+ ions were chosen as the dopants. The cubic spinel crystal structure of the synthesized ferrite samples was elucidated from the powder X-ray diffraction analysis. The crystallographic parameters associated with the samples were obtained from the Rietveld profile refinement of the diffraction patterns. The precise lattice parameter obtained from the Nelson-Riley extrapolation method is found nearly matches with the lattice parameter obtained from the Rietveld refinement of respective samples. The average crystallite size and microstrain accompanying with the samples were estimated from various methods such as via the Debye-Scherrer method, Williamson-Hall analysis and size-strain plot. By employing Tauc’s plot method, the optical parameters such as the direct bandgap, sub-bandgap and the Urbach energy of all the samples were calculated by analyzing the UV-Visible reflectance spectra. The room temperature magnetic properties of all the samples were estimated from the vibrating sample magnetometry. The nature of magnetic hysteresis revealed the semi-hard ferrimagnetism of the prepared cobalt ferrite samples. Also, the variation of magnetic properties with doping was analyzed. The weakening of interaction among the ions in tetrahedral and octahedral sites causes a decrease in the values of remanent magnetization, saturation magnetization and coercivity of doped samples.

Structural, surface, magnetic, and dielectric properties of Ni0.3Cu0.3Zn0.4Fe1.4Cr0.6O4 spinel ferrite nanocrystals prepared by sol-gel auto combustion route

Structural, surface, magnetic, and dielectric properties of Ni0.3Cu0.3Zn0.4Fe1.4Cr0.6O4 spinel ferrite nanocrystals prepared by sol-gel auto combustion route

Impact of magnetic spinel ferrite content on the structure, morphology, optical, and magneto-dielectric properties of BaTiO3 materials

Abstract In this study, the influence of magnetic content of NiFe1.93Dy0.07O4 spinel ferrite on the structural, morphological, optical, and magneto-dielectric properties of BaTiO3 materials was investigated. NiFe1.93Dy0.07O4 magnetic nanoparticles and BaTiO3 dielectric materials were firstly synthesized using the hydrothermal method and sol–gel auto-combustion route, respectively. Then, different contents of the magnetic nanoparticles were added to BaTiO3 to form a series of BaTiO3/(NiFe1.93Dy0.07O4) x samples (abbreviated as BTO/(NDFO) x ) with x = 0, 2, 5, 10, 20, and 100 %. The analysis of the structure via X-ray diffraction (XRD) technique revealed a transformation from a tetragonal structure for the pristine BTO sample to a cubic structure upon the inclusion of magnetic nanoparticles. The morphological observations and chemical composition analyses via scanning electron microscope (SEM) coupled with EDX system showed the successful formulation of biphasic products. The optical properties were investigated, and it was found that the inclusion of the magnetic phase diminishes the bandgap energy (E g ) of final BTO/(NDFO) x samples. Furthermore, vibrating sample magnetometer (VSM) was used to investigate the magnetization properties. The values of saturation magnetization (M S ) and remanent (M r ) magnetization are rising with the increase of magnetic phase content. However, the coercivity (H c ) does not show a regular variation with the increase of NDFO content. The dielectric properties were also investigated for different BaTiO3/(NiFe1.93Dy0.07O4) x samples. The obtained results showed that the real permittivity (ε′) and dielectric tangent loss (tan δ) increased with increasing temperature. Remarkably, the addition of magnetic content provokes a reduction in tan δ values compared to the pristine BTO sample. The lowest values of tan δ and highest frequency stability were noticed in the sample added with 10 % of magnetic phase. The impedance and modulus were also determined and discussed.

Zircon-Type CaCrO4 Chromite Nanoparticles: Synthesis, Characterization, and Photocatalytic Application for Sunlight-Induced Degradation of Rhodamine B.

The degradation of organic dye pollutants is a critical environmental issue that has garnered significant attention in recent years. To address this problem, we investigated the potential of CaCrO4 chromite (CCO) as a photocatalyst for the degradation of cationic and anionic dye solutions under sunlight irradiation. CaCrO4 was synthesized via a sol-gel auto-combustion route and sintered at 900 °C. The Rietveld refined XRD profile confirmed the zircon-type structure of CaCrO4 crystallized in the tetragonal unit cell with I41/amd space group symmetry. The surface morphology of the sample was investigated by field emission scanning electron microscopy (FESEM), which revealed the polyhedral texture of the grains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) studies were carried out to analyze the elemental composition and chemical states of the ions present in the compound. Fourier transform infrared (FT-IR) spectroscopy analysis revealed the vibrational modes corresponding to the tetrahedral and dodecahedral metal oxide bonds. The optical band gap was approximated to be in the range of 1.928 eV by using the Tauc relation. The CaCrO4 catalyst with different contents (5, 20, 35, and 50 mg) was investigated for its photocatalytic performance for the degradation of RhB dye solution under sunlight irradiation using a UV-Vis spectrometer over the experimental wavelength range of 450-600 nm. The degradation efficacy increased from 70.630 to 93.550% for 5-35 mg and then decreased to 68.720% for 50 mg in 140 min under visible light illumination. The comparative study demonstrates that a higher degradation rate was achieved for cationic than anionic dyes in the order RhB > MB > MO. The highest deterioration (93.80%) was achieved for the RhB dye in 140 min. Equilibrium and kinetic studies showed that the adsorption process followed the Langmuir isotherm and pseudo-second-order models, respectively. The maximum adsorption capacity of 21.125 mg/g was observed for the catalyst concentration of 35 mg. From the cyclic test, it has been observed that the synthesized photocatalyst is structurally and morphologically stable and reusable. The radical trapping experiment demonstrated that superoxide and hydroxyl radicals were the primary species engaged in the photodegradation process. A possible mechanism for the degradation of RhB has been proposed. Hence, we conclude that CaCrO4 can be used as an efficient photocatalyst for the remediation of organic dye pollutants from the environment.