Polyaniline/CoFe2O4 nanocomposite inhibits the growth of Candida albicans 077 by ROS production

In recent years, polyaniline/CoFe₂O₄ nanocomposites have gained attention because of their wide utilization in optoelectronics and biomedical studies. However, very limited research has been carried out on the anticandidal activity of polyaniline/CoFe₂O₄ nanocomposite against Candida spp. Thus, the study was designed to investigate the anticandidal potential of PANI/CoFe₂O₄ nanocomposite against Candida albicans 077. PANI/CoFe₂O₄ nanocomposite (denoted as “cfPNCs”) was synthesized by polymerization of aniline in the presence of CoFe₂O₄ nanoparticles. The structural and thermal properties of the synthesized PANI/CoFe₂O₄ nanocomposite were investigated. It was noteworthy that PANI/CoFe₂O₄ nanocomposite showed promising anticandidal activity in a dose-dependent manner. Results also showed that the protection of histidine (a ROS quencher) against ROS clearly suggested the implication of ROS in anticandidal activity of PANI/CoFe₂O₄ nanocomposite. It is encouraging to conclude that PANI/CoFe₂O₄ nanocomposite bears the potential of their applications in biomedicine, especially nanotherapy for diseases caused by C. albicans.     

CoFe2O4@TiO2@Au Core-Shell Structured Microspheres: Synthesis and Photocatalyltic Properties

A facile and efficient method for fabrication of magnetic composite microspheres CoFe₂O₄@TiO₂@Au is demonstrated. The shells of anatase TiO₂ were coated onto a magnetic CoFe₂O₄ core via liquid-phase deposition procedure, and then Au nanoparticles were deposited onto CoFe₂O₄@TiO₂ microspheres through seed-mediated growth. XRD, TEM, and VSM were used to investigate the structure, morphology and magnetic properties of the samples, their photocatalytic activity were also tested. Heterostructure of CoFe₂O₄@TiO₂@Au was confirmed by different measurements. Compared to unmodified CoFe₂O₄@TiO₂ microspheres, CoFe₂O₄@TiO₂@Au microspheres showed higher photocatalytic activity for Rhodamine B (RhB) degradation in water.

     

Adsorption characteristics of Titan yellow and Congo red on CoFe2O4 magnetic nanoparticles

This paper assesses the adsorption characteristics of Titan yellow and Congo red on CoFe₂O₄ magnetic nanoparticles. The adsorption behavior of Titan yellow and Congo red from aqueous solution onto CoFe₂O₄ magnetic nanoparticles has been determined by investigating the effects of pH, concentration of the dye, amount of adsorbent, contact time, ionic strength and temperature. Experimental results indicated that CoFe₂O₄ nanoparticles can remove more than 98 % of each dye under optimum operational conditions of a dosage of 15.0 mg CoFe₂O₄, pH 3.0, initial dye concentration of 22–140 mg L^?1, and contact times of 2.0 and 15.0 min for Congo red and Titan yellow, respectively. Langmuir and Freundlich isotherm models have been used to evaluate the ongoing adsorption kinetic equations. Regeneration of the saturated adsorbent was possible by NaCl/acetone solution as eluent. The maximum adsorption capacities were 200.0 and 212.8 mg dye per gram adsorbent for Congo red and Titan yellow, respectively. With the help of adsorption isotherm, thermodynamic parameters such as free energy, enthalpy and entropy have been calculated. On the basis of pseudo-first-order and pseudo-second-order kinetic equations, different kinetic parameters have been obtained.     

Decoration of MWCNTs with CoFe2O4 Nanoparticles for Methylene Blue Dye Adsorption

In the present work, a simple and viable method for producing multi-walled carbon nanotubes (MWCNTs) decorated with CoFe₂O₄ nanoparticles is presented. Chemical composition and crystal structure of the CoFe₂O₄/MWCNT composite was confirmed by X-ray diffraction measurements, while transmission electron microscopy was used to characterize the morphology and the distribution of nanocrystals in the composite. The obtained particles with relatively small diameter (about 14.9?nm) were found to be dispersed on the carbon nanotubes. The adsorption of methylene blue dye on CoFe₂O₄/MWCNT composites has been investigated. CoFe₂O₄/MWCNT composites show high adsorption capacity for methylene blue dye. Both Langmuir and Freundlich models describe the adsorption isotherms very well and the adsorption thermodynamic parameters (?G ⁰, ?H ⁰ and ?S ⁰) were calculated. The adsorption of methylene blue is generally spontaneous and thermodynamically favorable. The adsorption of methylene blue involves an endothermic process.     

Nickel and cobalt ferrites nanoparticles: synthesis,study of magnetic properties and their use as magnetic adsorbent for removing lead(II) ion

Nano-sized nickel ferrite (NiFe₂O₄) and cobalt ferrite particles (CoFe₂O₄) were successfully synthesized using a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscope, Fourier transform infrared spectrometer, energy dispersive X-ray spectroscopy, vibrating sample magnetometer and transmission electron microscope have been used to characterize and study the as-synthesized NiFe₂O₄ and CoFe₂O₄ products. The results showed that the average size of the nickel and cobalt ferrite nanoparticles is smaller than 10 and 100 nm, respectively. The results of magnetic measurement showed that the synthesized NiFe₂O₄ and CoFe₂O₄ nanoparticles were superparamagnetic and soft ferromagnetic materials, respectively. Study of adsorption behavior showed that these nanoparticles can act as a good adsorbent for removing Pb²⁺.     

Calcination-Free Synthesis of Well-Dispersed and Sub-10 nm Spinel Ferrite Nanoparticles as High-Performance Anode Materials for Lithium-Ion Batteries: A Case Study of CoFe2O4

Spinel ferrites are promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacities. However, their practical application is impeded by inherent low conductivity and severe volume expansion, which can be surpassed by increasing the surface-to-volume ratio of nanoparticles. Currently, most methods produce spinel ferrite nanoparticles with large size and severe aggregation, degrading their electrochemical performance. In this study, a low-temperature aminolytic route was designed to synthesize sub-10 nm CoFe₂O₄ nanoparticles with good dispersion through carefully exploiting the reaction of acetates and oleylamine. The performance of CoFe₂O₄ nanoparticles obtained by a traditional co-precipitation method was also investigated for comparison. This work demonstrates that CoFe₂O₄ nanoparticles synthesized by the aminolytic route are promising as anode materials for LIBs. Besides, this method can be extended to design other spinel ferrites for energy storage devices with superior performance by simply changing the starting material, such as MnFe₂O₄, MgFe₂O₄, ZnFe₂O₄, and so on.     

β−cyclodextrins-based inclusion complexes of CoFe2O4 magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection

β−cyclodextrins (β−CD)-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol-hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of β−CD-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles and naked CoFe₂O₄ magnetic nanoparticles on the luminol-hydrogen peroxide CL system was investigated. It was found that inclusion complexes between β−CD and CoFe₂O₄ magnetic nanoparticles could greatly enhance the CL of the luminol-hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol-hydrogen peroxide system demonstrates that addition of CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 × 10⁻⁷ to 4.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 2.0 × 10⁻⁸ mol L⁻¹ under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.     

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization M_s and remenant magnetization M_r increased as the calcination temperature increased. But the variation of coercivity H_c was not in accordance with that of M_s and M_r, indicating that H_c is not determined only by the crystallinity and size of CoFe₂O₄ nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe₂O₄ nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe₂O₄ nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile.     

Ultrasound-assisted synthesis of CoFe2O4/Ce-UiO-66 nanocomposite for photocatalytic aerobic oxidation of aliphatic alcohols

During the past years, light-driven selective oxidation of various alcohols has attracted increasing attention as a green and eco-friendly manner to convert visible light energy into valuable compounds. In this work, magnetic CoFe₂O₄/Ce-UiO-66 embedded structure composites are elaborately designed for the photocatalytic oxidation of aliphatic alcohols under visible-light irradiation and aerobic condition at room temperature. The CoFe₂O₄/Ce-UiO-66 structure was prepared using a simple and fast ultrasound-assisted technique in 60 min at room temperature. As compared with the unmodified CoFe₂O₄, the embedded composite exhibited better visible-light sensitization performance. The catalyst showed high chemical stability in the reaction conditions and can be recovered quickly and reused for at least five reaction runs in the aerobic oxidation reaction condition.     

High-yield synthesis and characterization of monodisperse sub-microsized CoFe2O4 octahedra

In this study, sub-microsized CoFe₂O₄ octahedra with a high yield are synthesized via a simple hydrothermal route under mild conditions. The as-prepared products are characterized by conventional techniques of XRD, SEM, TEM, ED and HR-TEM. The results show that the as-synthesized sample exhibits octahedral morphology with a narrow size distribution. The edge size of CoFe₂O₄ octahedra is estimated to be about 0.10-0.14 μm. The growth process is also monitored by time and temperature-dependent observation. It is found that the reaction temperature has no obvious influence on the product morphology but a significant effect on the size of CoFe₂O₄ octahedra, while the reaction time determines the final morphology of the product. Moreover, it is displayed that the citrate ions play a key role in the formation of CoFe₂O₄ octahedra. Furthermore, the possible growth mechanism of the sub-microsized CoFe₂O₄ octahedra is discussed on the basis of a series of experiments. Magnetic measurements show that sub-micro-sized CoFe₂O₄ octahedra exhibit obvious ferromagnetic behaviors. The saturation magnetization (M_s), remanent magnetization (M_r), and coercivity (H_c) are determined to be 85.8, 29.2 emu/g and 892 Oe, respectively.     

Preparation of magnetic CoFe2O4-functionalized graphene sheets via a facile hydrothermal method and their adsorption properties

Magnetic CoFe₂O₄-functionalized graphene sheets (CoFe₂O₄-FGS) nanocomposites have been synthesized by hydrothermal treatment of inorganic salts and thermal exfoliated graphene sheets. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that cobalt ferrite nanoparticles with sizes of 10-40 nm are well dispersed on graphene sheets. OH⁻ was recognized as a tie to integrate the inorganic salts with the graphene sheets, which made reaction started and developed on the surface of graphene sheets and formed cobalt ferrite nanoparticles on graphene sheets. The adsorption kinetics investigation revealed that the adsorption of methyl orange from aqueous solution over the as-prepared CoFe₂O₄-FGS nanocomposites followed pseudo-second-order kinetic model and the adsorption capacity was examined as high as 71.54 mg g⁻¹. The combination of the superior adsorption of FGS and the magnetic properties of CoFe₂O₄ nanoparticles can be used as a powerful separation tool to deal with water pollution.     

An easy synthesis of nanostructured magnetite-loaded functionalized carbon spheres and cobalt ferrite

An easy method in a solvothermal system has been developed to synthesize nanostructured magnetite (Fe₃O₄)-loaded functionalized carbon spheres (CSs) and cobalt ferrite (CoFe₂O₄). Surface-tunable CSs loaded with iron oxide (Fe₃O₄) nanoparticles were prepared using an acetylferrocene Schiff base (OPF), whereas spinel cobalt ferrite (CoFe₂O₄) was synthesized via metal complexes of a ferrocenyl Schiff base with phenol moiety (Co-OPF). The formed composite powder was investigated using X-ray powder diffraction, Raman spectrometry, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. It was found that most of the iron oxide nanoparticles were evenly distributed upon the surface of the CSs. Furthermore, the surface of the iron oxide-loaded CSs has large numbers of functional groups. Good saturation magnetization was achieved for the formed magnetic nanoparticles.     

Glycol-assisted autocombustion synthesis of spinel ferrite CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles: magnetic and electrochemical performances

Uniform spinel ferrite CoFe₂O₄ nanoparticles with average diameter of 40 nm were fabricated by a novel glycol-assisted autocombustion method. The as-prepared powders were characterized by X-ray diffraction, transmission electron microscopy and Raman spectrum. The room temperature magnetic property of the nanoparticles was examined, indicating the presence of an ordered magnetic structure in the spinel system. The electrochemical tests show that the as-prepared nanoparticles exhibits excellent electrochemical cycleability. The simple synthetic route can be applied to as a general method for the fabrication of other functional nanomaterials.     

Ligand‐Induced Evolution of Intrinsic Fluorescence and Catalytic Activity from Cobalt Ferrite Nanoparticles

To develop CoFe₂O₄ as magneto‐fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe₂O₄ NPs with Na‐tartrate. Moreover, the functionalized CoFe₂O₄ NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe₂O₄ NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe₂O₄ NPs hold great promise for advanced biomedical and technological applications.     

Electrochemical performance of spindle-like Fe2Co-MOF and derived magnetic yolk-shell CoFe2O4 microspheres for supercapacitor applications

Nanostructured cobalt ferrite (CoFe₂O₄) has been synthesized by a two-step process, a facile ultrasonic-assisted solvothermal technique for Fe₂Co-MOF preparation and subsequent calcination. X-ray diffraction (XRD) patterns confirm the formation of MIL-88A(Fe) structure of Fe₂Co-MOF and the cubic spinel structure of CoFe₂O₄. Field emission scanning electron microscope (FESEM) images reveal that calcination process converts the spindle-like morphology of Fe₂Co-MOF to yolk-shell CoFe₂O₄ microspheres. From Brunauer–Emmett–Teller (BET) analysis, the specific surface areas of 36.0 and 29.2 m² g^?1 are measured for Fe₂Co-MOF and CoFe₂O₄, respectively. Vibrating sample magnetometer (VSM) analysis of CoFe₂O₄ displays high coercivity of 2500 Oe due to surface anisotropy. Conversion of Fe₂Co-MOF to CoFe₂O₄ reduces the optical band gap from 1.92 to 1.77 eV. Electrochemical performance of Fe₂Co-MOF and CoFe₂O₄ deposited on Ni foams (NFs) is examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests. Specific capacitances of 489.9 and 192.6 F g^?1 have been achieved from GCD curves at a current density of 1 A g^?1 for Fe₂Co-MOF/NF and CoFe₂O₄/NF electrodes, respectively. Fe₂Co-MOF/NF electrode exhibits more cyclic stability than CoFe₂O₄/NF electrode after 3000 cycles.

     

铁酸钴纳米粒子:室温下点击合成亚芳基巴比妥酸衍生物的高效可磁性分离多相催化剂(英文)

A coprecipitation method was used to synthesize superparamagnetic CoFe2O4 nanoparticles without using any capping agents/surfactants. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, a vibrating sample magnetometer (VSM), N2 adsorption and thermogravimetric/differential thermal analysis/differential thermal gravimetry techniques. The synthesized spinel CoFe2O4 nanoparticles had an average size of 2-8 nm with a high surface area (140.9 m2/g). The field-dependent magnetization, demonstrated by VSM and saturation magnetization, was found to be 1.77 emu/g. An efficient method was used for the synthesis of arylidene barbituric acid derivatives using CoFe2O4 magnetic nanoparticles as a magnetically separable and reusable catalyst in aqueous ethanol. The attractive features of this synthetic protocol were very short reaction time, high yields, high turnover frequency, simple work-up procedure, economy, a clean reaction methodology, and chemoselectivity, as well as provision of an ecofriendly and green synthesis.     

Cation distribution and particle size effect on Raman spectrum of CoFe2O4

Mössbauer and Raman spectroscopic studies were carried out on CoFe₂O₄ particles synthesized with size ranging from 6 to 500 nm (bulk). Cation distribution studies were carried out on the high temperature and room temperature phases of the microcrystalline CoFe₂O₄ by Mössbauer and Raman spectroscopic methods. The high temperature phase of CoFe₂O₄ showed a decreased inversion parameter of 0.69 as compared to the value of the room temperature phase of 0.95, indicating that the structure gradually transforms towards a normal spinel. Corresponding Raman spectra for these two phases of CoFe₂O₄ showed a change in relative peak intensity of the vibrational mode at 695 cm⁻¹(A_1g(1)) to 624 cm⁻¹ (A_1g(2)). The relative peak intensity ratio, I_v between the A_1g(1) and A_1g(2) vibrational mode was decreasing with lowering of inversion parameter of the CoFe₂O₄ spinel system. A variation of laser power on the sample surface was reflected in the cation distribution in ferrite phase. Superparamagnetic, single domain CoFe₂O₄ particles (6 nm) showed a 20 cm⁻¹ red shift and broadening of phonon modes when compared to the macro-crystalline CoFe₂O₄ (500 nm). Variation of Raman shift with particle size was studied by considering the bond polarization model. Raman spectroscopic studies clearly indicate the variation in the cation distribution in nano-sized particles and distribution tending to a normal spinel structural configuration.     

Interaction of Inorganic Nanoparticles with Graphene

The changes in the electronic and magnetic properties of graphene induced by interaction with semiconducting oxide nanoparticles such as ZnO and TiO₂ and with magnetic nanoparticles such as Fe₃O₄, CoFe₂O₄, and Ni are investigated by using Raman spectroscopy, magnetic measurements, and first‐principles calculations. Significant electronic and magnetic interactions between the nanoparticles and graphene are found. The findings suggest that changes in magnetization as well as the Raman shifts are directly linked to charge transfer between the deposited nanoparticles and graphene. The study thus demonstrates significant effects in tailoring the electronic structure of graphene for applications in futuristic electronic devices.     

Physico-chemical studies on thermal analysis of cobalt hexa(formato)ferrate(III) decahydrate

Thermal decomposition of cobalt hexa(formato)ferrate(III) decahydrate, Co₃[Fe(HCOO)₆]₂. 10H₂O, has been studied up to 973 K in static air atmosphere, employing TG, DTG, DSC, XRD, ESR, Mössbauer and infrared spectroscopic techniques. Dehydration occurs in two stages in the temperature range of 340–430 K. Immediately after the removal of the last water molecule the anhydrous complex undergoes decomposition till α-Fe₂O₃ and cobalt carbonate are formed at 588 K. In the final stage of remixing of cations, a solid state reaction between α-Fe₂O₃ and cobalt carbonate leads to the formation of CoFe₂O₄ at a temperature (953 K) much lower than for the ceramic method. A saturation magnetization value of 2310 Gauss of ferrite (CoFe₂O₄) shows its potential to function at high frequencies.     

等离子体修饰磁载TiO2光催化剂性能研究

以化学共沉法制备的CoFe₂O₄纳米粒子为磁核,采用TiCl₄水解包覆技术制备磁载二氧化钛纳米复合粒子CoFe₂O₄ /TiO_x(TCF),利用低温等离子体技术修饰TCF制备了CoFe₂O₄/TiO₂(PTCF)纳米复合光催化剂。运用VSM(振动样品磁强计)技术对样品磁性能进行研究,结果表明：等离子体修饰后的复合材料仍具有较高的饱和磁化强度,可在外加磁场作用下实现催化剂在水中的分离与回收;样品的XRD、TEM和UV-Vis分析测试结果表明：等离子体修饰后的复合材料有锐钛矿型TiO₂存在;TEM谱图显示磁核CoFe₂O₄的平均粒径约为20 nm,TCF复合粒子的粒径约为30~40 nm,TiO₂包覆层的厚度为10~20 nm。与纯TiO₂相比PTCF样品对光的吸收拓展到整个紫外-可见区,扩大了光谱响应范围;对甲基橙溶液降解的光催化活性评价研究表明：TCF复合粒子等离子体修饰后的PTCF纳米复合光催剂的光催化活性明显提高。