α-Bi2O3 nanosheets: An efficient material for sunlight-driven photocatalytic degradation of Rhodamine B

Herein, we report the sunlight driven photocatalytic degradation of toxic organic dye, Rhodamine B using α-Bi₂O₃ nanosheets as an effective photocatalyst. The α-Bi₂O₃ nanosheets were prepared by simple annealing assisted thermal decomposition method and characterized by several techniques in order to understand its morphological, compositional, structural and optical properties. Morphological, structural and compositional investigations confirmed the formation of sheet-like morphologies, high-crystalline monoclinic crystal structure, and pure α-Bi₂O₃, respectively. The synthesized α-Bi₂O₃ nanosheets exhibited a high photocatalytic degradation of a toxic organic dye, i.e. Rhodamine B (RhB). Under optimal reaction conditions, ～95% photocatalytic degradation of RhB (10 mg/L, pH 10) was observed in 180 min using 0.75 g/L catalyst dosage under sunlight irradiation. According to the findings, the synthesized catalyst had outstanding photocatalytic properties and can be used to cleanse textile wastewater under direct sunlight.     

The structural evolution and optical properties of Mg1-xZnxAl1.8Cr0.2O4 pink ceramic pigments

In this work, pink ceramic pigments based on the composition of Mg_1-xZn_xAl_1.8Cr_0.2O₄(x = 0.0,0.3,0.5,0.7,1.0) were synthesized by using a gel polymerization method. We focused on studying the effect of A-site ion doping on the random cation distribution, microstructure and optical absorption performance. Field Scanning electron microscopy (FESEM), X-ray diffraction (XRD) and the Rietveld refinement method with a GSAS program were applied for micromorphology and cation distribution analyses. The optical performance of the pigments was studied by UV–vis and CIE L*a*b* spectrophotometry. All samples had a single spinel phase within the calcination temperature range of 800 °C–1400 °C and the primary grain size of the synthesized pigments were approximately 0.5–1 μm. The ion distribution in the tetrahedron and octahedron was largely dependent upon the calcining temperature and composition. The oxygen parameter, cell parameter, and T-O and M-O band lengths also varied with the cation distribution, leading to a change in the spinel structure and octahedron crystal field parameter and ultimately changing the optical absorption properties of the synthetic pigments. This study lays the foundation for subsequent studies of colour modification in ceramics.     

Investigation of structural,optical, and magnetic properties of Nd-doped Sr2SnO4 Ruddlesden Popper oxide

The samples of Sr_2-xNd_xSnO₄ with x = 0, 0.01, 0.02, 0.04, 0.06, and 0.10 were synthesized by a high-temperature solid-state ceramic route. Rietveld refining of X-ray diffraction results showed that all the synthesized compositions are single phase under tetragonal crystal structure. The presence of functional group and local structure has been studied using FTIR and Raman spectroscopy, respectively. XPS study of samples showed the presence of oxygen vacancy and interstitial oxygen in the sample. Optical band gap of samples analyzed by UV-Vis spectra gradually increases with dopant concentration, and Photoluminescence (PL) spectroscopy study showed most intense emission around 1064 nm. Room-temperature magnetic hysteresis curve in sample SSN2 showed ferromagnetism, slowly decreasing with Nd and becoming antiferromagnetic for higher compositions. Utilizing the absorption state observed in PL as metastable state makes it promising candidate for laser and IR detector application and the ferromagnetic/antiferromagnetic nature of sample makes it suitable candidate for spintronics device applications.     

Effects of molten-salt processing parameters on the structural and optical properties of preformed La2Zr2O7:Eu3+ nanoparticles

Molten-salt method has been used to synthesize various functional materials, but it has not been employed to adjust the structure, particle size, and properties of preformed particles. To fill the knowledge gap, in this study, we use a molten-salt medium to reprocess preformed La₂Zr₂O₇:5%Eu³⁺ nanoparticles which were already formed by a molten-salt synthesis (MSS) method. The molten-salt processing is conducted under various conditions in terms of processing time, temperature, and medium. Specifically, within the studied molten-salt processing time (0 h–24 h) at 800°C, 3 h was found to offer the best optical output. In terms of the investigated molten-salt processing temperature (650 °C–1100 °C) for 3 h, 800 °C was identified as the most desirable annealing temperature. Regarding the explored molten-salt processing media (nitrate vs. chloride) at 3 h and 800 °C, better luminescence results were obtained for nanoparticles processed in chloride. Under each processing parameter, the change of optical properties is explained based on the balance among the crystalline size, crystal structure, crystallinity, defect, and agglomeration characteristics of the molten salt processed La₂Zr₂O₇:5%Eu³⁺ particles. We expect this study will excite other scientists to further explore molten-salt processing as an effective post-synthesis method to fine-tune the structure, particle size, and properties of preformed particles to meet the demand of functional materials.     

Study of the changes in the structure and optical properties of MgxCo1-xCr2-yAlyO4 spinel caused by A/B site ion substitution

In this work, nanosubmicron blue-green pigment powder based on the composition of Mg_xCo_1-xCr_2-yAl_yO₄（0 = x ≤ 1, 0 = y ≤ 2）was prepared by a gel casting method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Rietveld refinement with GSAS (General Structure Analysis System), and UV–Vis absorption spectroscopy were used to study the phase composition, grain size, morphology, cation distribution in the crystal structure and spectral absorption of the samples. Colour parameters were also studied by using a colour measurement spectrophotometer. The studies demonstrate that the distribution of cations in the crystal structure is disordered and that divalent and trivalent cations are mixed to occupy tetrahedral and octahedral sites. Furthermore, the substitution of ions at the A/B site leads to a change in the cation distribution ratio at the tetrahedral and octahedral sites. With increasing Mg²⁺ doping concentration, the inversion parameter of the spinel increases, while with increasing Al³⁺ doping concentration, the inversion parameter of the spinel decreases. In addition, changes in the calcining atmosphere lead to a change in the oxygen vacancy content in the structure. Under the condition of a reductive atmosphere, the oxygen vacancy content significantly increases, and the inversion parameter also increases. The colour difference for the synthesized Mg_xCo_1-xCr_2-yAl_yO₄ spinel powder is related to the proportion of chromophore ions occupying tetrahedral and octahedral sites and the number of oxygen vacancies.     

Investigation of the microstructure,cation distribution and optical properties of nanoscale NixMg1-xAl2O4 spinel pigments

Nanoscale Ni_xMg_1-xAl₂O₄ spinel pigments were synthesized by a citric acid precursor combined with the gel-casting method. The microstructure, cation distribution and optical properties as a function of calcining temperature and nickel content were investigated by the X-ray diffraction (XRD) Rietveld refinement, transmission/field emission scanning electron microscopy (TEM/FESEM), X-ray photoelectron spectroscopy (XPS), colour measurement and UV–vis–NIR spectrophotometry. Upon increasing the calcining temperature, both Ni²⁺ and Mg²⁺ hindered the migration of Al³⁺ to octahedral sites. When the Ni content increased, the cation site percentage of Ni²⁺ in the tetrahedral and octahedral sites varied slightly while that of Al³⁺ and Mg²⁺ change substantially. The cation exchange resulted in an increase in the inversion parameters and a decrease in the lattice parameters with increasing temperature or Ni content. Furthermore, Rietveld refinement also showed a shrinkage of the tetrahedra and an expansion of the distorted octahedra in the spinel structure. Short-range information based on optical spectra suggests that variation in the splitting energy of tetrahedra and octahedra caused the change in the spectral absorption. This study may deepen the understanding of the structural-optical property relationship of Ni_xMg_1-xAl₂O₄ spinel, which is vital to the further colour modification of ceramics and glazes.     

Enhanced structural,optical, and photocatalytic activity of novel Cd–Zn co-doped Mg0.25 Fe1.75O4 for degradation of RhB dye under visible light irradiation

Cd_xZn_1-xMg_0.25Fe_1.75O₄ (where x = 0.00, 0.25, 0.50, 0.75, 1.00) have been successfully produced by a facile hydrothermal technique for a thorough comparison of structural, optical, and photocatalytic properties (degradation of Rhodamine B -RhB dye under visible light irradiation). X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed the formation of cubic spinel structure for all of the samples. Fourier transform infrared (FTIR) spectroscopy verified the presence of metal-oxygen (M–O) bonding in the prepared samples with two frequency bands corresponding to phonon vibrational stretching in both the octahedral and tetrahedral lattice positions. UV–Visible Spectrophotometer and photoluminescence (PL) spectroscopy investigated the bandgap variation (2.7 eV-1.7 eV) and emission spectrum peaks appearing in the range of 405–471 nm region. The comparison in the photo-degradation of Rhodamine B (RhB) revealed the superior performance (98% degradation of RhB dye in 80 min having a K value of 0.04966 with excellent reusability) of Cd_0.50Zn_0.50Mg_0.25Fe_1.75O₄ sample having 50/50 dopant ratio of Cd and Zn in the parent Mg Ferrite, attributed to the lowest bandgap, longer lifetime of charge carriers, active octahedral lattice site, electron/hole pair recombination preventions, and the least value of ohmic impedance at higher frequency.     

Phase evolution,structure, and electrochemical performance of Al-, Ga- and Ta- substituted Li7La3Zr2O12 ceramic electrolytes by a modified wet chemical route

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is one of the most promising solid-state electrolytes (SSEs) for advanced solid-state lithium batteries (SSLBs). In this work, Li_6.25Al_0.25La₃Zr₂O₁₂, Li_6.4Ga_0.2La₃Zr₂O₁₂, and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ ceramics are prepared by a modified wet chemical route. The composition of the black mixtures derived from the precursors is ascertained. The phase evolution and structural properties from the ceramic mother powders to the final ceramic electrolytes are discussed in detail. The characteristic of cubic LLZO with the space group I-43d arises in the Li_6.4Ga_0.2La₃Zr₂O₁₂ ceramic electrolyte pellet after the secondary higher-temperature (1200 °C) sintering. The Rietveld refinement reveals the roles of Al³⁺ substitution at the Li⁺ sites and Ta⁵⁺ substitution at the Zr⁴⁺ sites to adjust crystal structure. In addition, the electrochemical performance of the ceramic pellets is also investigated. Remarkably, the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ ceramic electrolyte has the most outstanding electrochemical performance, showing the high ionic conductivity of 6.88 × 10^?4 S cm^?1 (25 °C), the low activation energy of 0.42 eV and an extremely low electronic conductivity of 1.77 × 10^?8 S cm^?1 (25 °C). Overall, it is supposed that this work may help to achieve high-quality modified LLZO ceramic electrolytes, especially using the wet chemical strategy.     

Ag-Co3O4: Synthesis,characterization and evaluation of its photo-catalytic activity towards degradation of rhodamine B dye in aqueous medium

Synthesis,characterization of Co_3O_4 and Ag-Co_3O_4 composites and evaluation of their photo-catalytic activities towards photo-degradation of aqueous solution of rhodamine B dye under irradiation of visible light have been described in this paper.Co_3O_4 was prepared by solid phase mechano chemical process using Co(NO_3)_2·6H_2O and NH_4 HCO_3 as precursor materials.Ag was deposited on Co_3O_4 from AgNO_3 using Calotropis gigantea extract as reducing agent.XRD,SEM and FTIR were used for characterization of prepared composites.Photo-catalytic efficiencies of as-prepared Co_3O_4 and Ag-Co_3O_4 were evaluated for aqueous phase photo-degradation of rhodamine B.It was found that deposition of Ag on Co_3O_4 highly enhanced the photo-catalytic activity of Co_3O_4.Photo-catalytic degradation followed the Eley–Rideal mechanism.About 100% and 91% photo-degradation of 40 ml dye solution achieved at 313 K in 90 and 120 min over 0.05 g of Ag-Co_3O_4 as photo-catalyst using 100 and 200 mg·L~(-1) as initial concentration of dye respectively.     

Role of Ni2+ substituent on the structural,optical and magnetic properties of chromium oxide (Cr2-xNixO3) nanoparticles

Pristine chromium oxide (Cr₂O₃) and nickel ions (Ni²⁺) substituted Cr₂O₃ nanoparticles were synthesized using a simple co-precipitation technique. The main objective of this work is to investigate Ni²⁺ substituent's role at different concentrations on the structural, morphological, optical, and magnetic properties of Cr₂O₃ nanoparticles. Structural analyses based on X-ray diffraction (XRD), Raman and Fourier transform infra-red (FTIR) data confirmed the successful incorporation of Ni²⁺ into Cr₂O₃ nanoparticles up to x = 0.05 of Ni²⁺ content, without affecting the rhombohedral crystal structure of Cr₂O₃ nanoparticles. Rietveld refinement results showed the variation in lattice parameters and cell volumes alongwith the substitution of Ni²⁺ into Cr₂O₃ nanoparticles. Raman and FTIR spectra also depicted a considerable shift in the characteristic vibration modes of Cr₂O₃ nanoparticles due to strain-induced by Ni²⁺ substitution. Beyond x = 0.05, the structural transformation took place from rhombohedral to cubic crystal structure. Subsequently, new peaks (apart from Cr₂O₃ phase modes) have been observed at x = 0.1 of Ni²⁺ content due to the formation of secondary phase i.e., nickel chromate (NiCr₂O₄). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) illustrated the changes in the morphology of Cr₂O₃ nanoparticles with Ni²⁺ substitution. UV–Vis analysis revealed a narrowing of optical band energy (E_g) of Ni²⁺ substituted Cr₂O₃ nanoparticles from 3 to 1.85 eV as Ni²⁺ content varies from x = 0 to 0.2, respectively. Afterward, there is an increase in optical band gap energy (E_g) when Ni²⁺ content increased from x = 0.3 to 0.5, as NiCr₂O₄ started dominating the Cr₂O₃ phase. Single-phase Ni²⁺ substituted Cr₂O₃ nanoparticles exhibited a superparamagnetic behavior, whereas the multi-phase compound ascribed to both superparamagnetic and paramagnetic. These changes in optical and magnetic properties can lead to novel strategies to render applications in the field of optoelectronics and optomagnetic devices.     

One-pot synthesis of 3D porous Bi7O9I3/N-doped graphene aerogel with enhanced photocatalytic activity for organic dye degradation in wastewater

The compound Bi₇O₉I₃ has been considered as a promising candidate for organic dye degradation in wastewater, but it has relatively low photocatalytic activity and difficulties in the recycling processes. In this work, a novel floating 3D porous Bi₇O₉I₃/N-doped graphene aerogel (Bi₇O₉I₃/NGA) composite was successfully synthesized through a facile hydrothermal route. The Bi₇O₉I₃/NGA composite exhibited highly enhanced photocatalytic performance toward degrading rhodamine B under visible-light irradiation, which increased 6.0 and 2.3 times compared with the Bi₇O₉I₃ and Bi₇O₉I₃/GA, respectively. The enhancement of photocatalytic degradation activity could be ascribed to the extensively promoted charge generation and migration efficiency, visible light utilization ability and reactive oxygen species production. Besides, the special 3D macroscopic block structure of Bi₇O₉I₃/NGA allowed it to float, making it easy to recycle. The photocatalytic degradation efficiency of Bi₇O₉I₃/NGA composite still could reach up to 92.7% after four consecutive cycles and presented satisfactory stability and reusability. Moreover, a possible photocatalytic degradation mechanism was revealed by radical species trapping and semi-quantitative analyses experiments.     

Efficient sunlight and UV photocatalytic degradation of Methyl Orange,Methylene Blue and Rhodamine B,using Citrus×paradisi synthesized SnO2 semiconductor nanoparticles

In this work, tin dioxide (SnO2) Nanoparticles (NPs) were synthesized through green synthesis, using Citrus × paradisi extract as a stabilizing (capping). The extract concentrations used were 1, 2 and 4% in relation to the aqueous solution. The resulting SnO2 NPs were used for the degradation of Methyl Orange (MO), Methylene Blue (MB) and Rhodamine B (RhB), under both solar and UV radiation. The NPs were characterized via Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM-SAED), the Brunauer-Emmett-Teller (BET) theory, Ultraviolet to Visible spectroscopy (UV–Vis), and Photoluminescence spectroscopy (PL); while the photocatalytic degradation was evaluated using UV-VIS. The results showed that the Citrus × paradisi extract is a good medium for the formation of SnO2 NPs. These NPs presented quasi-spherical morphology, particle sizes of 4–8 nm, with a rutile phase crystalline structure, and with banned gap of 2.69 at 3.28 eV. The NPs had excellent photocatalytic properties under solar radiation, degrading 100% of the OM in 180 min. Furthermore, under UV radiation, 100% degradation of the three dyes was achieved in a short time; 20 min for MO, and 60 min for MB and RhB. Therefore, green synthesis is a feasible medium for the formation of SnO2 NPs with good photocatalytic properties.     

Effect of Ni2+ substitution on structural,magnetic, dielectric and optical properties of mixed spinel CoFe2O4 nanoparticles

Nanoparticles of Co_1−xNi_xFe₂O₄ with x=0.0, 0.10, 0.20, 0.30, 0.40 and 0.50 were synthesized by co-precipitation method. The structural analysis reveals the formation of single phase cubic spinel structure with a narrow size distribution between 13–17 nm. Transmission electron microscope images are in agreement with size of nanoparticles calculated from XRD. The field emission scanning electron microscope images confirmed the presence of nano-sized grains with porous morphology. The X-ray photoelectron spectroscopy analysis confirmed the presence of Fe²⁺ ions with Fe³⁺. Room temperature magnetic measurements showed the strong influence of Ni²⁺ doping on saturation magnetization and coercivity. The saturation magnetization decreases from 91 emu/gm to 44 emu/gm for x=0.0–0.50 samples. Lower magnetic moment of Ni²⁺ (2 µ_B) ions in comparison to that of Co²⁺ (3 µ_B) ions is responsible for this reduction. Similarly, overall coercivity decreased from 1010 Oe to 832 Oe for x=0.0–0.50 samples and depends on crystallite size. Cation distribution has been proposed from XRD analysis and magnetization data. Electron spin resonance spectra suggested the dominancy of superexchange interactions in Co_1−xNi_xFe₂O₄ samples. The optical analysis indicates that Co_1−xNi_xFe₂O₄ is an indirect band gap material and band gap increases with increasing Ni²⁺ concentration. Dispersion behavior with increasing frequency is observed for both dielectric constant and loss tangent. The conduction process predominantly takes place through grain boundary volume. Grain boundary resistance increases with Ni²⁺ ion concentration.     

Influence of Gd2O3 on the microstructure and properties of transparent MgAl2O4: Cr3+ ceramic

In this work, MgAl₂O₄: Cr³⁺ transparent ceramics have been synthesized by the hot press sintering techniques, and the effect of the sintering aid Gd₂O₃ and its content on the densification, microstructure, and optical, photoluminescence was studied and discussed. The relative density reached 99.29% with 0.8 wt% Gd₂O₃ as a sintering aid, and the optical transmittance at 686 nm and 1446 nm were approximately 76%. As Gd₂O₃ content continued to increase, the grain size of the ceramics became smaller and uniform, accompanied by some pores with the size of ～1 μm. The ceramics with 4.0 wt% Gd₂O₃ showed a higher transmittance, of 82% at 1446 nm. Additionally, Gd₂O₃ was helpful for Cr³⁺ in the sites of octahedral symmetry, which increased the quantum yield. The quantum yield of MgAl₂O₄: Cr³⁺ with 0.8 wt% Gd₂O₃ was about 0.175, which was 36% higher than that of ceramic without Gd₂O₃. In short, the sintering aid Gd₂O₃ not only contributed to improving the densification, homogenizing the grain size, and heightening the optical transmittance but also enhanced the quantum yield of Cr³⁺.     

Anatase TiO2 powder immobilized on reticulated Al2O3 ceramics as a photocatalyst for degradation of RO16 azo dye

The three-dimensional network of open-celled Al₂O₃ ceramic supports were first fabricated using a polymeric sponge replication technique. The polyurethane foams soaked with the highly loaded Al₂O₃ ceramic slurry were drained, slowly dried and sintered at 950 °C to complete the burn out process and to construct the ceramic preforms. They were then carefully soaked again with the moderately loaded Al₂O₃ slurry and sintered at 1500 °C to increase their strength. Finally, the photocatalyst ceramic powder covering the outer surfaces was placed layer by layer through dipping the rigid Al₂O₃ supports repeatedly in the slurry of TiO₂ powder. The dip-applied TiO₂ was sintered eventually at relatively low temperature of 700 °C to prevent phase transformation. The efficiencies of the TiO₂ coated Al₂O₃ samples were evaluated by the photocatalytic degradation of reactive orange 16 (RO16) azo dye molecules dissolved in water. Nearly complete color removals were achieved within 75 min under UVC irradiation.     

A new nanocluster polyoxomolybdate [Mo_(36)O_(110)(NO)_4(H_2O)_(14)]·52H_2O:Synthesis,characterization and application in oxidative degradation of common organic dyes

Polyoxomolybdate [Mo_(36)O_(110)(NO)_4(H_2 O)_(14)]·52 H_2 O was synthesized by a simple one-pot procedure through reducing an acidified mixture of Na_2 MoO_4·2 H_2 O and NH_2 OH·HCl. In order to create a heterogeneous catalyst system, the polyoxomolybdate was pillared with MgAl-LDH-NO_3 by direct ion exchange. These novel materials were carefully analyzed by various chemico-physical methods. The catalytic degradation of methylene blue(MB) and rhodamine B(RB) as common dyes in the presence of MgAl-LDH-1 nanoparticles with aqueous hydrogen peroxide, H_2 O_2, as an oxidizing agent was studied in aqueous solution at room temperature. More importantly, the catalyst can be recovered and reused efficiently up to five consecutive cycles with negligible loss of catalytic activity.     

Influence of silicon carbide on structural,optical and magnetic properties of Wollastonite/Fe2O3 nanocomposites

The influence of adding 10, 20 and 30% molar ratio of silicon carbide (SiC) separately to a composite of wollastonite (W) with a fixed content of 10%Fe₂O₃ prepared by wet precipitation method was studied. The crystal structure of the annealed composite powders was inspected by X-ray diffraction (XRD); revealing multi-phase structure. The highest estimated crystallite size investigated by Scherrer equation of W, SiC, WFe:SiC₁₀, WFe:SiC₂₀ and WFe:SiC₃₀ were 53.89, 54.6, 56.3, 48.5 and 54.6 nm respectively; demonstrating the formation of nanocomposites. Particles shape, size and crystallinity of the samples were studied using high resolution transmission electron microscope (HR-TEM). The band gap E_g values of the nanocomposites increased with SiC content having an intermediate value that lies between that of γ-Fe₂O₃ (maghemite) and SiC. Ferromagnetic and paramagnetic contributions were observed in the magnetic hysteresis loops for the composites. This study highlighted that the coercive field (H_ci) of the composites improved with increasing the SiC content. The innovative wollastonite/Fe₂O₃/SiC with amended magnetic properties elicited attention due to their promising application in bone filler and industrial purposes.     

Influence of Cr and Fe doping on the structure,magnetic and optical properties of nano CuCo2O4

Nano CuCo_2-xM_xO₄ (x = 0, 0.1, 0.2, M = Cr or Fe) samples were synthesized by hydrothermal method. Synchrotron x-ray diffraction data obtained for the samples were subjected to phase analysis and manifested a single-phase cubic spinel structure for Cr-doped samples, while for Fe-doped samples two phases were identified. Cation distribution and cell parameter (a) were obtained from Rietveld X-ray diffraction analysis. FTIR analysis affirmed the formation of the cubic spinel and the cation distribution obtained. The nano nature of the samples and the particle morphology were examined by high-resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). UV-diffuse reflectance revealed that all samples have two optical energy gaps. For all Fe doped samples, the optical band gaps decreased, while for Cr-content x = 0.1 the bandgaps increased then reduced for x = 0.2. Doped samples exhibited a blue or red shift depending on the kind and amount of the dopant ions. The PL intensity and the emitted colors depended on the kind and amount of the dopant ions. Magnetic measurements disclosed the paramagnetic nature of CuCo₂O₄, while a weak ferromagnetic is revealed for CuCo_2-xCr_xO₄ and a ferromagnetic nature for CuCo_2-xFe_xO₄. Lowering the bandgap upon doping could make better mobility of lattice oxygen and enhancing the catalyst reducibility. Thus, the Cr and Fe-doped samples are expected to have better catalytic activity than the pristine one.     

Optimization,structural, optical and magnetic properties of TiO2/CoFe2O4 nanocomposites

Magneto-optical TiO₂/xCoFe₂O₄ nanocomposites having various concentrations of CoFe₂O₄ (x = 2, 4 and 6 wt %) were prepared using facile mechanical mixing. X-ray diffraction was employed for the phase examination and microstructure parameters. X-ray diffraction spectra proved the formation of two separate phases: tetragonal titanium dioxide (TiO₂) and face-centered cubic cobalt iron oxide. The structure was further verified by recognizing the selected area electron diffraction (SAED) pattern recorded by a high-resolution transmission microscope. The optical investigation of the prepared nanocomposites verified that the optical band gap values varied from 3.1 eV for pure TiO₂ to 3.05 eV for TiO₂/CoFe₂O₄ (6 wt %). The refractive index, optical dielectric constant and loss factor were discussed in detail. The nanocomposites (TiO₂/xCoFe₂O₄) demonstrated ferromagnetic characteristics and their magnetic parameters were affected by the CoFe₂O₄ percentage in the composites. The sample x = 2 wt % depicted the maximum magnetic exchange bias at room temperature. Moreover, it showed maximum coercivity (H_C) and magnetic squareness ratio (SQ), which makes it suitable for spintronic applications.