Aqueous Co-precipitation Method Research Articles

Synthesis of Silane Functionalized LDH-Modified Nanopowders to Improve Compatibility and Enhance Corrosion Protection for Epoxy Coatings.

Novel modified Zn-Al LDH/epoxy coatings are synthesized and applied to steel substrates, providing active corrosion protection and improved barrier properties. This protective coating is made by combining Epon 828 as a polymer matrix with modified layered-double-hydroxy (LDH) nanoparticles acting as corrosion inhibitor containers. To synthesize the coatings, nitrate was intercalated into Zn-Al-LDH layers through an aqueous co-precipitation method to obtain Zn-Al LDH-NO3, and decavanadate replaced nitrate within the LDH layers through an anion exchange process to obtain Zn-Al LDH-(V10O28)6-. The intercalated LDH was functionalized by silanization with (3-aminopropyl)triethoxysilane (APTES) to increase the compatibility of the LDH inhibitor nanocontainers with epoxy resin and produce a protective coating. To protect the mild steel substrate, functionalized LDH nanopowders were dispersed into the epoxy resin, mixed with a polyamide hardener (Epikure 3571), and applied and cured to the metal surface. Surface morphology, structure, and chemical composition were determined for the modified LDH nanopowders using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Corrosion protection of the coating system was studied using long-term immersion testing and potentiodynamic polarization studies in a 3.5 wt.% NaCl solution.

“Adsorptive removal of Congo Red dye from its aqueous solution by Ag–Cu–CeO2 nanocomposites: Adsorption kinetics, isotherms, and thermodynamics”

Eliminating synthetic dyes and organic contaminants from water is crucial for safeguarding human health and preserving the environment. In this study, we explored the effectiveness of Ag–Cu–CeO2 nanocomposites as adsorbents to remove Congo Red dye from water. Three compositions of Ag–Cu–CeO2 nanocomposites (10:20:70, 15:15:70, and 20:10:70) have been synthesized by the aqueous coprecipitation method. A comprehensive analysis was performed by different techniques including X-ray diffraction, Fourier transform infrared spectroscopy, BET surface area determination, Thermogravimetric analysis, Scanning electron microscopy, and TEM. The synthesized nanocomposites have a dimension of 5 ± 1 nm and a high surface area (51.832–78.361 m2g-1).Among these, the nanocomposite with composition 15:15:70 showed the highest adsorption capacity of 4.71 mg/g adsorption (96.83 % removal) from the 0.8 × 10−4 M (55.6 mg/l) Congo Red solution at pH values of 2 at 20 °C with contact time of 3h. The adsorption data is best fitted in the Freundlich adsorption isotherm and pseudo-second-order kinetic model. The negative values of enthalpy variation (−27.57, −26.43, and −16.73 kJ/mol) demonstrated that the adsorption was spontaneous and exothermic. The cycling run showed a mere 12 % deactivation after five cycles of use thus indicating that Ag–Cu–CeO2 nanocomposites hold great potential as effective and eco-friendly adsorbents to remove Congo Red from water.

Exploring the impact of pH on the properties of citric acid-coated iron oxide nanoparticles as high-performance T2 contrast agent for MRI applications

Iron oxide nanoparticles (IONPs) were synthesized using an aqueous co-precipitation method at various pH levels ranging from 8 to 12. The impact of solution pH on IONPs' properties was analyzed by studying their size, shape, and surface charge. Both the crystalline structure and size of IONPs were significantly affected by pH levels, as revealed by X-ray diffraction analysis. Across all pH values, magnetite was found to be the predominant phase. Interestingly, the smallest nanoparticle size was observed at pH 10. The IONPs synthesized at the optimal pH were then coated with citric acid to be used as contrast agents in Magnetic Resonance Imaging (MRI). The citric acid coating was applied to the IONPs to increase their biocompatibility and optimize their dispersity. The coated samples were further characterized using Zetasizer, Fourier-Transform Infrared Spectroscopy (FTIR), and Vibrating Sample Magnetometry (VSM). The results indicated high stability and appropriate magnetization, with a relaxivity ratio (r2/r1) of 73.75, making citric acid-coated IONPs a promising candidate for use as T2 MRI contrast agents. FTIR, Zetasizer, and VSM measurements indicated that the citric acid coating had a positive effect on the biocompatibility, stability, and magnetization of the IONPs. IONPs are excellent T2 MRI contrast agents because of their enhanced physiochemical properties, and their high relaxivity ratio confirms their effectiveness. The findings of this study emphasize the crucial role that pH plays in determining the properties of IONPs and highlight the potential use of citric acid-coated IONPs in medical imaging applications such as MRI.

The Influence of Medium on Fluorescence Quenching of Colloidal Solutions of the Nd3+: LaF3 Nanoparticles Prepared with HTMW Treatment.

An original method was proposed to reduce the quenching of the NIR fluorescence of colloidal solutions of 0.1 at. % Nd3+: LaF3 nanoparticles (NPs) synthesized by aqueous co-precipitation method followed by hydrothermal microwave treatment. For this, an aqueous colloidal solution of NPs was precipitated by centrifugation and dissolved in the same volume of DMSO. The kinetics of static fluorescence quenching of Nd3+ donors of doped NPs dispersed in two solvents was analyzed to determine and to compare the concentrations of OH- quenching acceptors uniformly distributed throughout the volume of the NPs. The dependences of the relative fluorescence quantum yield φ of colloidal solutions on the concentration of OH- groups in the NPs were calculated and were also used to determine concentration of acceptors in the volume of NPs in different solvents. It was found that the concentration of OH- groups in NPs dispersed in DMSO is almost two times lower than in NPs dispersed in water. This gives an almost two-fold increase in the relative fluorescence quantum yield φ for the former. The sizes of synthesized NPs were monitored by common TEM and by applying a rapid procedure based on optical visualization of the trajectories of the Brownian motion of NPs in solution using a laser ultramicroscope. The use of two different methods made it possible to obtain more detailed information about the studied NPs.

Na1.51 Fe[Fe(CN)6 ]0.87 ·1.83H2 O Hollow Nanospheres via Non-Aqueous Ball-Milling Route to Achieve High Initial Coulombic Efficiency and High Rate Capability in Sodium-Ion Batteries.

Prussian blue analogues (PBAs) have attracted extensive attention as cathode materials in sodium-ion batteries (SIBs) due to their low cost, high theoretical capacity, and facile synthesis process. However, it is of great challenge to control the crystal vacancies and interstitial water formed during the aqueous co-precipitation method, which are also the key factors in determining the electrochemical performance. Herein, an antioxidant and chelating agent co-assisted non-aqueous ball-milling method to generate highly-crystallized Na2- x Fe[Fe(CN)6 ]y with hollow structure is proposed by suppressing the speed and space of crystal growth. The as-prepared Na2- x Fe[Fe(CN)6 ]y hollow nanospheres show low vacancies and interstitial water content, leading to a high sodium content. As a result, the Na-rich Na1.51 Fe[Fe(CN)6 ]0.87 ·1.83H2 O hollow nanospheres exhibit a high initial Coulombic efficiency, excellent cycling stability, and rate performance via a highly reversible two-phase transition reaction confirmed by in situ X-ray diffraction. It delivers a specific capacity of 124.2 mAh g-1 at 17mA g-1 , presenting ultra-high rate capability (84.1 mAh g-1 at 3400mA g-1 ) and cycling stability (65.3% capacity retention after 1000 cycles at 170mA g-1 ). Furthermore, the as-reported non-aqueous ball-milling method could be regarded as a promising method for the scalable production of PBAs as cathode materials for high-performance SIBs.

Ga2O3(Sn) Oxides for High-Temperature Gas Sensors.

Gallium(III) oxide is a promising functional wide-gap semiconductor for high temperature gas sensors of the resistive type. Doping of Ga2O3 with tin improves material conductivity and leads to the complicated influence on phase content, microstructure, adsorption sites, donor centers and, as a result, gas sensor properties. In this work, Ga2O3 and Ga2O3(Sn) samples with tin content of 0–13 at.% prepared by aqueous co-precipitation method were investigated by X-ray diffraction, nitrogen adsorption isotherms, X-ray photoelectron spectroscopy, infrared spectroscopy and probe molecule techniques. The introduction of tin leads to a decrease in the average crystallite size, increase in the temperature of β-Ga2O3 formation. The sensor responses of all Ga2O3(Sn) samples to CO and NH3 have non-monotonous character depending on Sn content due to the following factors: the formation of donor centers and the change of free electron concentration, increase in reactive chemisorbed oxygen ions concentration, formation of metastable Ga2O3 phases and segregation of SnO2 on the surface of Ga2O3(Sn) grains.

Promising Antimicrobial and Azo Dye Removal Activities of Citric Acid-Functionalized Magnesium Ferrite Nanoparticles

In this study magnesium ferrite nanoparticles (MgFe2O4 NPs) were synthesized through an aqueous co-precipitation method and functionalized with citric acid (CA) for outstanding their antimicrobial potential and removal activity of azo dye. MgFe2O4 NPs and CA-MgFe2O4 NPs were characterized by XRD, HRTEM, SEM, EDX, FT-IR, and SEM/EDX mapping method to analyze crystallinity, average particle size, morphology, functional groups and elemental composition, respectively. Antimicrobial activity was investigated against pathogenic bacteria and yeast as zone of inhibition (ZOI) and minimum inhibitory concentration (MIC). Reaction mechanism using SEM/EDX analysis of CA-MgFe2O4 NPs-treated microbial cells was mentioned. The removal efficiency was tested against methyl orange (MO), and various parameters affecting the removal efficiency such as (pH on removal of MO, MO initial concentration, and CA-MgFe2O4 dose) were studied. Antimicrobial results showed that CA-MgFe2O4 NPs demonstrated maximum activities against S. aureus, E. coli, and C. albicans with ZOI of 20.0, 16.0, and 14.0 mm, respectively. Results obtained suggested that 0.1 g of CA-MgFe2O4 NPs achieved 85.0% removal of MO at pH 5.0.0, hence, it exhibited efficient dye removal and sufficient antimicrobial activities.

Synthesis of BaTi5O11 by an aqueous co-precipitation method via a stable organic titanate precursor

BaTi5O11 has been widely researched due to its unique microwave properties. Conventionally, it is challenging to obtain this compound as a single phase. The BaTi5O11 was synthesized via a co-precipitation technique using an aqueous solution of titanium(IV)(triethanolaminato) isopropoxide, barium nitrate and ammonia as precursors, which are stable in aqueous media. The phase evolution, purity, and structure were identified by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy analysis. The desired BaTi5O11 structure was obtained by calcination at 900?C. Furthermore, the structure was characterized by TGA, FT-IR and Raman studies. The study showed that the particles were between 80 and 120 nm in size and the average crystallite size was determined from the Scherrer formula as 68.1 nm at 900?C.

Evaluation of the Antimicrobial Activity of Citric Acid Functionalized Magnetite Nanoparticles

Background: Antimicrobial resistance (AMR) has emerged as one of the principal public health problems of the 21st century that threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria no longer susceptible to the common medicines used to treat them. Objectives: To development of Fe3O4 NPs with specific sizes and shapes Potential as a new antibacterial agent. Methodology: In this study magnetite nanoparticles (Fe3O4 NPs) were synthesized through an aqueous co-precipitation method and functionalized with citric acid for outstanding their antimicrobial potential. Fe3O4 NPs were characterized by XRD, TEM, SEM, EDX and FTIR to analyze crystallinity, average particle size, morphology and functional groups, respectively. Antimicrobial activity was investigated against pathogenic bacteria as zone of inhibition (ZOI) and minimum inhibitory concentration (MIC). Results: Antimicrobial results showed that CA- Fe3O4 NPs owns maximum activity against Staphylococcus aureus and E. coli by 18.0 and 15.0mm ZOI, respectively. Conclusion: It should be noted that (CA-Fe3O4) NPs are also active upon Gram-positive than Gram- negative bacteria. The synthesized (CA-Fe3O4) NPs are promising for potential applications as antimicrobial agent and in drug delivery fields.

Structural, optical, electrical and thermo-electrical properties of Cu doped Co9S8-NPs synthesized via co-precipitation method

Pure and copper doped cobalt sulphide (Co9S8) nanoparticles were synthesized using aqueous chemical co-precipitation method. To study the effect of elemental composition Cu (0%, 1%, 5%, 10% &15%) on structural, optical, electrical and thermoelectric properties of Co9S8 nanoparticles were investigated using various characterization techniques such as XRD, SEM, FTIR, UV–VIS and two probe methods. Cubic structure and grain size of pure and Cu doped Co9S8-NPs was confirmed by X-ray diffraction and SEM analysis. FTIR spectrum showed the different rotational and vibrational mode attached on the surface of the material. A redshift appeared in the band gap value (Eg) as a function of the Cu dopant and high absorbance in the optical region makes the material suitable for photocatalytic activity. The electrical result show that conductivity increases and resistivity decreased as Cu content increases in Co9S8-NPs. Finally, thermoelectric measurements referred to the unique critical temperature for each sample where current starts rising exponentially.

Effect of Strontium Doping on the Band Gap of $$\hbox {CeO}_{2}$$ CeO 2 Nanoparticles Synthesized Using Facile Co-precipitation

Pure, 3 mol% and 5 mol% Sr-doped cerium oxide nanoparticles were synthesized by facile aqueous co-precipitation method using cerium nitrate hexahydrate and strontium chloride hexahydrate as the precursors without using any capping agent. The synthesized material was characterized by XRD, SEM, EDX, TEM, Raman spectroscopy and UV–Vis spectroscopic techniques. SEM analysis showed agglomeration of the particles. The Debye–Scherrer analysis revealed fluorite structure of the synthesized material with crystallite size in 6–10 nm range. TEM confirmed the spherical morphology of the particles and particle size distribution in the range of 5–8 nm. UV–Vis spectroscopic study revealed that Sr-doping led to increase in the band gap from 3.2 to 3.7 eV and shifting of absorption edge to the lower wavelength. The blue shift in the band gap with the dopant concentration shows that the band gap of doped cerium oxide nanoparticles can be tuned with variation in the dopant concentration.

Impact of rGO on photocatalytic performance of Cd-doped ZnO nanostructures synthesized via a simple aqueous co-precipitation route

Zinc oxide (ZnO), cadmium-doped zinc oxide (CZO), zinc oxide/reduced graphene oxide (ZnO-rGO) and cadmium-doped zinc oxide/reduced graphene oxide (CZO-rGO) nanostructures were synthesized successfully using a simple and rapid aqueous co-precipitation method at room temperature. The structure, morphologies, composition and optical properties of these samples were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), Raman and UV–vis spectroscopy, respectively. In order to achieve a synergic effect, both Cd concentration, and impact of rGO on photocatalytic performance of Cd-doped ZnO nanostructures were investigated. The photocatalytic activities of the samples were investigated with the degradation of methylene blue (MB) under sunlight and showed excellent photocatalytic degradation performance for CZO-rGO (5% Cd) compared to the other samples. Facile and low-temperature synthesis process with the excellent degradation performance demonstrates that the CZO-rGO nanocomposites have a great potential for wastewater treatment applications.

Enhanced UV and visible light—driven photocatalytic degradation of tartrazine by nickel-doped cerium oxide nanoparticles

Nickel-doped cerium oxide nanoparticles were synthesized via a simple aqueous co-precipitation method. The synthesized nanoparticles were thoroughly characterized by PXRD, TEM, SEM, EDX, Raman, and UV–vis spectroscopic techniques. XRD study revealed the formation of nanoparticles in their pure phase with fluorite structure. EDX confirmed the doping of nickel in the cerium oxide lattice. The shift in Raman spectra revealed the formation of a solid solution on doping Ni- to CeO2. SEM images revealed considerable agglomeration. TEM analysis asserted the average particle size of 8–10 nm with a well defined spherical shape. The particle size was found to be sensitive to dopant concentration i.e., it decreased with increase in the concentration of the dopant. A comparative UV-visible spectroscopic analysis showed the remarkable red shift in the band gap of nickel-doped cerium oxide nanoparticles. Investigation of photocatalytic activity towards degradation of azo dye tartrazine showed that 3 mol% and 5 mol% Ni- CeO2 nanoparticles exhibited 53.4% and 63.7% photodegradation respectively under visible irradiation while 57.4% and 65.4% respectively under UV irradiation. The study suggests that band gap of cerium oxide nanoparticles can be easily tuned (decreased) by doping of nickel at different concentrations. The observed improved photocatalytic activity upon Nickel doping is attributed to the narrow band gap.

Solvent free nanoscale ionic materials based on Fe3O4 nanoparticles modified with mussel inspired ligands

Mussels exhibit robust adhesion capability with varied materials mainly due to the strong affinity of catechol moieties in their adhesive proteins. Nanoscale ionic materials (NIMs) are special organic-inorganic hybrid materials comprising a charged oligomer corona attached to inorganic nanoparticle cores, which can behave from glassy solids to liquids in the absence of any solvent. Herein, Fe3O4 nanoscale ionic materials (NIMs) exhibiting inorganic-organic core-shell structure and liquid-like behavior were obtained by using a mussel-inspired bifunctional ligand of 3,4-dihydroxybenzenepropanoic acid (DHPA), which could link Fe3O4 nanoparticles core and cationic organic shell, respectively. A simplified one-step aqueous co-precipitation method to prepare DHPA decorated Fe3O4 nanoparticles is developed, which shows advantages in productivity and is more environmental friendly compared with the traditional core preparation first and then surface modification. This research proposes a simple and effective approach to obtain solvent-free NIMs with tailorable core-shell structure using versatile adhesion of mussel mimetic adhesives and various available ion pairs.

Eu3+ or Sm3+-Doped terbium-trimesic acid MOFs: Highly efficient energy transfer anhydrous luminophors

[Tb(TMA):RE3+] MOFs (MOF: Metal Organic Framework; TMA: trimesic acid or 1,3,5-benzenetricarboxylic acid, RE3+: Eu and Sm) with tunable color were synthesized by aqueous coprecipitation method. Using a chemical artifice, lanthanide cationic radius contraction, it was possible to obtain only anhydrous MOFs, a very important characteristic in luminescent compounds. TMA3− anions triplet states present higher energy levels compared to the main emitting states of Eu3+ (5D0), Tb3+ (5D4) and Sm3+ (4G5/2), supplying an efficient antenna effect. Based on the spectroscopic investigation, i.e. excitation/emission spectra and lifetimes of the excited states, the material shows a high quantum efficiency (η = 83–86%) due to the very efficient energy transfer process TMA→Tb→Eu, combined to the presence of this high energy absorption ligand and the absence of water molecules.

The Effect of Polypyrrole in the Capacity Retention of Fe3O4/Polypyrrole Composite Electrodes in Lithium-Ion Batteries

Future device applications will dictate increases in the energy density of batteries, which may be accomplished by incorporating high capacity electroactive materials into composite electrodes where all the electroactive material is electrochemically accessible and the mass and volume contributions of passive components are minimized. Electroactive materials are incorporated into batteries through the fabrication of composite electrodes, where several additives may be used to enhance conductivity and to mechanically bind the components. Typically, an electrically conductive carbon additive (e.g. acetylene black or graphite) and a polymer binder (e.g. PVDF and PTFE) are mixed with the electroactive material to form a composite electrode. Electrically conducting polymers are intriguing as composite electrode additives since conceptually they can fulfill the roles of both carbon and binder. Magnetite is a naturally occurring mineral found in the earth’s crust; therefore, it is abundant, environmentally friendly, cheap, and non-toxic. Magnetite is also easy to synthesize and can be prepared through simple, non-hazardous techniques such as through a facile aqueous co-precipitation method. Complete reduction of magnetite involves the transfer of 8 electrons, providing opportunity for an impressive capacity of 925 mAh/g. Notably, the initial reactions are insertion reactions where the lithium ion can insert into the Fe3O4 structure with minimal structural distortion, while upon further reduction, a conversion reaction occurs generating Fe metal and Li2O as products of full discharge. To further probe the role of the electrically conductive polymer in the mesoscale (bulk) properties of composite electrodes, this study focuses on the Fe3O4 conversion reaction and its relationship to the electrically conductive polymer binder, PPy, including a detailed study of composite electrodes with nanoscale Fe3O4 and PPy. Magnetite, Fe3O4, with 6% and 20% polypyrrole (PPy) was used to prepare composite electrodes with and without added carbon. Galvanostatic cycling and Electrochemical Impedance Spectroscopy (EIS) measurements were used in tandem to determine delivered capacity, capacity retention, and the related impedance at various stages of discharge and charge. Further, the reversibility of Fe3O4 to iron metal conversion observed during discharge was quantitatively assessed, ex situ, using X-ray Absorption Spectroscopy (XAS). The Fe3O4 composite containing the largest weight fraction of PPy (20 wt%) with added carbon demonstrated reduced irreversible capacity on initial cycles and improved cycling stability over 50 cycles. This study illustrated the beneficial role of PPy addition to Fe3O4 based electrodes partially related to improved electrical conductivity and also to improved ion transport related to the formation of a more favorable surface electrolyte interphase (SEI).

Comparison between microwave and conventional calcination techniques in regard to reactivity and morphology of co-precipitated BaTiO3 powder, and the electrical and energy storage properties of the sintered samples

Barium titanate (BaTiO3) nanopowders were synthesized by an aqueous co-precipitation method followed by calcination. Either 2.45GHz microwaves or conventional heating was used in order to investigate the impact of these techniques on the synthesis time, microstructure, and electrical properties of the materials. The heating temperatures ranged from 620°C to 810°C. X-ray diffraction (XRD) revealed pure BaTiO3 formation by microwave heating in a noticeably shorter time (five minutes) compared to conventional heating (3h). Field emission scanning electron microscopy (FESEM) results confirmed that the microwave process led to nanocube formation, whereas in the conventional procedure, the particles tended to form spherical shapes. To evaluate the electrical properties, the samples heated at 620°C were conventionally sintered at 1280°C, 1330°C, and 1380°C. Higher dielectric, piezoelectric, and ferroelectric properties and more energy-saving efficiency (εr=1012, tanδ=0.035 d33=85 pC/N, pr=6.2µC/cm2 and η=48% respectively) were achieved in the microwave-heated BaTiO3 sintered at 1380°C compared to the conventionally heated BaTiO3 (εr=824, tanδ=0.030 d33=75 pC/N, pr=5µC/cm2 and η=27%) demonstrating that microwave calcination substantially affects the final electrical properties.

Alkaline Earth Element Adsorption onto PAA-Coated Magnetic Nanoparticles

In this paper, we present a study on the adsorption of calcium (Ca2+) onto polyacrylic acid-functionalized iron-oxide magnetic nanoparticles (PAA-MNPs) to gain an insight into the adsorption behavior of alkaline earth elements at conditions typical of produced water from hydraulic fracturing. An aqueous co-precipitation method was employed to fabricate iron oxide magnetic nanoparticles, whose surface was first coated with amine and then by PAA. To evaluate the Ca2+ adsorption capacity by PAA-MNPs, the Ca2+ adsorption isotherm was measured in batch as a function of pH and sodium chlorite (electrolyte) concentration. A surface complexation model accounting for the coulombic forces in the diffuse double layer was developed to describe the competitive adsorption of protons (H+) and Ca2+ onto the anionic carboxyl ligands of the PAA-MNPs. Measurements show that Ca2+ adsorption is significant above pH 5 and decreases with the electrolyte concentration. Upon adsorption, the nanoparticle suspension destabilizes and creates large clusters, which favor an efficient magnetic separation of the PAA-MNPs, therefore, helping their recovery and recycle. The model agrees well with the experiments and predicts that the maximum adsorption capacity can be achieved within the pH range of the produced water, although that maximum declines with the electrolyte concentration.

Effect of pH on electrical and magnetic properties of Al3Fe5O12 nanoparticles

Al3Fe5O12 (AIG) nanopowders were synthesized at different pH using aqueous co-precipitation method. The effect of pH on the phase formation of AIG is characterized using XRD, TEM and TG/DTA. From Scherrer formula the average crystallite sizes were found to be 20, 25, 28 and 32 nm for pH 9, 10, 11 and 12. From TEM micrographs, the particle sizes of the powders were found to be 15, 21, 25 and 30 nm for pH 9, 10, 11 and 12, respectively. It is found that as the pH of the solution increase the particle size also increases. It is clear from the TG/DTA curves that as the pH is increasing the weight losses were found to be small. The obtained nanopowders were further sintered at 900 °C/4 h using conventional sintering method. The phase formation is completed at 800 °C which is correlated with TG/DTA. X-ray photoelectron spectroscopy is used to study the electronic state of the AIG sample. The average grain size of the samples is found to be ~55 nm. Room temperature magnetization measurements established these compounds to be soft magnetic. The room temperature dielectric and magnetic properties (e′, e″, µ′ and µ″) of AIG was studied over a wide range of frequency 1 MHz–1.8 GHz. The dielectric constant was found to decrease with increasing frequency. With increase of pH both e′ and µ′ increased. The Curie temperature was confirmed to be from 560 K (~287 °C) based on the dielectric anomaly observed when these measurements were carried out over a temperature range of 300–600 K. The ferromagnetic resonance linewidth is found to be increasing from 77 to 142 Oe and the effective saturation magnetization (4πMeff) is found to be higher compare to effective saturation magnetization (4πMs) by VSM. This finding provides a new route for AIG materials could be useful for various applications for spintronics.

High rates of Cr(VI) photoreduction with magnetically recoverable nano-Fe 3 O 4 @Fe 2 O 3 /Al 2 O 3 catalyst under visible light

Abstract Core-shell type Fe 3 O 4 @Fe 2 O 3 was dispersed over nano Al 2 O 3 support using aqueous medium co-precipitation method. The Fe 3 O 4 core offers magnetic recoverability, while the shell Fe 2 O 3 , due to its optimal band gap, provides photocatalytic activity in the visible light region. The concentration of Fe 3 O 4 @Fe 2 O 3 was varied and the synthesized materials were characterized using XRD, TEM, XPS, Raman spectroscopy, diffuse reflectance spectroscopy and BET surface area measurement. The synthesized materials were studied for Cr(VI) visible light photoreduction. Oxalic acid was used as a hole scavenger and Cr(VI) was efficiently reduced under visible light in aerobic condition. Even with 5% Fe 3 O 4 @Fe 2 O 3 /Al 2 O 3 the rate of photoreduction was orders of magnitude higher than that of bulk Fe 3 O 4 @Fe 2 O 3 . The obtained rates with the synthesized catalysts were compared with the literature and were found to be superior to the reported catalysts. The 40% Fe 3 O 4 @Fe 2 O 3 /Al 2 O 3 catalyst showed magnetic recoverability and the catalytic efficiency was stable up to 4 cycles.