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In this research paper, we have reported the thermal, structural, magnetic and optical properties of unsubstituted and aluminum substituted zinc ferrite nanoparticles. These substituted and unsubstituted ferrite nanoparticles were prepared by cost effective co-precipitation method. The co-precipitated unannealed nanoparticles of the typical sample were subjected to thermogravimetric analysis (TGA) to probe the annealing temperature. The X-rays diffraction (XRD) technique was used for the determination of structural parameters. XRD patterns of all compositions of Al x ZnFe 2-x O 4 nanoparticles confirmed the FCC structure of these spinel ferrite nanoparticles. Besides the main crystal structure determination, many other lattice parameters and their variations with respect to increased Al3+ contents in ZnFe 2 O 4 were also calculated from XRD data and have been discussed in detail in this article. The morphology of the synthesized materials has been studied by scanning electron microscopy (SEM) and average particles size found < 100 nm. The variation in electrical and magnetic parameters with increased Al3+ contents was studied in detail. The analysis of magnetic properties concluded that the prepared nanoparticles have good magnetic properties. At the end the optical studies of the nanoparticles proved that these spinel ferrites also have photocatalytic applications. The photocatalytic degradation of methylene blue in the presence of these samples has been studied and discussed. The ferrites particles could be separated from contaminated water simply by magnetic bars. Therefore these particles can be used and recycled easily for photocatalytic applications. The aim of work was to study the structural, electrical, magnetic and catalytic behavior of the material. [ABSTRACT FROM AUTHOR]

Abstract In this work erbium (Er3+) substituted cobalt zinc ferrite having general formula Co 0.70 Zn 0.30 Er x Fe 2-x O 4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were fabricated using micro-emulsion technique. The substitution of Er was done for the purpose of tuning the optical band gap. Er+3 substituted nanoparticles were annealed at 700 °C for 7 h. A typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 was utilized to make the nanocomposites material with reduced graphene oxide (rGO), that was prepared by facile chemical route. The main purpose of graphene was to enhance the conductivity of ferrite particles. All these ferrite particles and a composite were characterized by X-rays diffraction (XRD), UV–Visible spectroscopy and SEM for structural elucidation and morphology studies. Single phase spinel structure was confirmed by XRD analysis and crystallized size calculated by Scherer formula was found in the range 35–60 nm. SEM confirmed the well dispersed ferrite particles among graphene sheets. All the Er-substituted ferrite particles were subjected to dielectric parameters study. One typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 particles and its composites with rGO were utilized for photocatalysis study using methylene blue as model organic compound in the presence of visible light. Current-voltage (I-V) measurements of ferrites nanoparticles and their composites with graphene were also studied. The results of all these techniques were agreed with each other and suggested the various potential applications of these nanoparticles. Highlights • Rare earth Er3+-substituted Cobalt-Zinc Nano-ferrites were prepared. • XRD confirmed the FCC structure of all compositions. • Graphene@ ferrite composites exhibited better photocatalytic properties. [ABSTRACT FROM AUTHOR]

Transition metal spinel type mixed oxides (FeCo 2 O 4 , MnCo 2 O 4 and ZnCo 2 O 4) nano-catalysts have been synthesized via co-precipitation route. The samples were characterized using XRD and FE-SEM techniques to determine structure and morphologies respectively. Furthermore, FTIR and BET analysis were carried out in order to confirm the structure and calculate surface areas of the samples. The photocatalytic potency of synthesized nano-catalysts have been examined for aqueous solution of methylene blue under visible light. It is found that photocatalytic activity of simple transition metal oxides was enhanced by making their binary/ternary metal oxides. FeCo 2 O 4 exhibited highest photocatalytic efficiency among the prepared spinel structures while MnCo 2 O 4 possess lowest efficiency. The photocatalytic behavior of mixed transition metal oxides can be accredited to its spinel structure, small particle size and large surface area. XRD and BET results revealed the small crystallite and particle size of spinel mixed oxides. The small crystallite size of spinel mixed oxides nano-structures contributes to increased photocatalytic activity by increasing the surface area of photocatalyst, decreasing the chance of reunion of charge carriers. It is observed that these binary oxide nano-structures have potential applications in heterogeneous photo decay of environmental contaminants and can act as propitious materials for resolving environmental issues and establishing green environment. • Spine oxide nano-catalysts were prepared via facile route. • Crystallite size was found < 10 nm. • All prepared nano-catalysts exhibited good photocatalytic activity. [ABSTRACT FROM AUTHOR]

A multipurpose, environment-friendly, and effective catalyst for control of environmental contaminants is an enduring interest in recent years. In the present study, lanthanum substituted spinel ferrite (La x MnFe 2-x O 4) nanoparticles were synthesized using an eco-friendly, low cost-effective reverse-micelle synthesis strategy. Thermal analysis was done to annualize the annealing temperature of prepared precipitates. X-ray diffraction (XRD) study revealed the well-defined cubic spinel structure of La x MnFe 2-x O 4 with the presence of a very minute secondary phase by the introduction of La3+ ion. Fourier transform infrared spectroscopy (FTIR) study confirmed the M − O metal-oxygen bond stretching at tetrahedral and octahedral sites. Surface morphology analyzed by field emission scanning electron microscopy (FESEM) revealed the narrow size distribution having nanoparticles size of nearly 60 nm. From the bandgap study, an enhanced redshift of 2.40 eV directed its semiconductor photocatalysis behavior. The degradation efficiency of pristine MnFe 2 O 4 and La3+ ion substituted MnFe 2 O 4 material was investigated using a contaminant crystal violet dye. Higher degradation efficiency, kinetic investigation smart degradation mechanism, and simple recovery suggested that the newly designed La3+ ion substituted MnFe 2 O 4 photocatalytic material is best for environmental remediation. [ABSTRACT FROM AUTHOR]

• Dy x MnFe 2- x O 4 nanoparticles decorated over mesoporous silica were synthesized. • High BET surface area of catalyst responsible for excellent adsorption. • The prepared catalyst also exhibited good photocatalytic activity. An efficient, environment-friendly and economical catalyst to control contaminants of environment is an enduring interest in recent years. In this study, a new composite, Dy x MnFe 2- x O 4 nanoparticles decorated over mesoporous silica was synthesized and utilized for removal of organic pollutant. Highly crystalline nature of Dy x MnFe 2- x O 4 nanoparticles and amorphous nature of material was confirmed by XRD (X-ray diffraction) technique. Infrared spectra of fabricated material before and after adsorption of dye molecules evidenced the successful adsorption of dye molecules by fabricated adsorbent. From field emission scanning electron microscopic (FESEM) images of Dy3+ substituted MnFe 2 O 4 composite with mesoporous silica, it was clearly observed that ferrite particles of size 20−30 nm were decorated on the surface of mesoporous silica particles and distributed well over spherical silica balls homogeneously. Its magnificent mesoporous nature was revealed from BET (nitrogen adsorption-desorption measurements) analysis. Surface area, pore volume and average pore size was found 387.95 m2/g, 0.390 cm3/g and 4.02 nm respectively. Tri-modal pore size distribution showed its effective utilization in adsorption. The abundant (Si OH) hydroxyl groups of mesoporous silica, the broad diffraction hump of silica depicted its superior loading capacity of target molecular specie inside its porous network. From band gap analysis, a red shift of 2.43 eV exhibited semiconductor photocatalysis of Dy x MnFe 2- x O 4 nanoparticles. Degradation efficiency of bare MnFe 2 O 4 , Dy x MnFe 2- x O 4 and mesoporous silica-based composite was tested using crystal violet dye. Its explored adsorption-photocatalysis synergy, degradation mechanism, kinetic investigation, easily recovery and remarkable recycling ability suggested that the new fabricated composite is best for environmental remediation. [ABSTRACT FROM AUTHOR]

The narrow optical band gap, higher electrical conductivity, and wider-absorption range are three key features that a good photocatalyst must possess. Herein, we have fabricated Cu-doped MnO 2 (Mn 1-x Cu x O 2) nanostructure by facile wet chemical approach and formed its nanocomposite with r-GO (Mn 1-x Cu x O 2 /r-GO) via ultra-sonication approach. The successful replacement of host metal ions (Mn4+) with the dopant metal ions (Cu2+) was supported with the PXRD, FT-IR, and EDX characterizations. The effect of Cu-doping on the band gap and r-GO matrix on the conductivity of the fabricated nanocomposite was also evaluated via Tauc plots and I–V tests, respectively. The photocatalytic efficiency of the fabricated photocatalysts was tested and compared against the methylene blue (MB) under visible light irradiation. The photocatalytic experiments revealed that Mn 1-x Cu x O 2 /r-GO photocatalyst exhibited superior photocatalytic aptitude than that of pristine MnO 2 and Mn 1-x Cu x O 2 photocatalysts. More precisely, the Mn 1-x Cu x O 2 photocatalysts degraded 86.89% MB dye at the rate of 0.021 min−1 after a 90-min exposure to the visible light. Observed superior catalytic activity of the nanocomposite can be attributed to the synergistic effects between the Cu doped MnO 2 and r-GO nanosheets that resulted in its narrow band-gap (2.19 eV) and excellent conductivity (2.217 × 10−2 Scm−1). [ABSTRACT FROM AUTHOR]