Search Results (94)

Accumulation of ferrous sulfate residue (FSR) not only occupies land but also results in environmental pollution and waste of iron resource; thus, recycling of iron from FSR has attracted widespread concern. To this end, this article shows fabrication and system analysis of hematite (HM) nanoparticles from FSR via microwave-assisted reduction technology. Physicochemical properties of HM nanoparticles were investigated by multiple analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible (UV-Vis) spectrum, vibrating sample magnetometer (VSM), and the Brunauer–Emmett–Teller (BET) method. Analytic results indicated that the special surface area, pore volume, and pore size of HM nanoparticles with the average particle size of 45 nm were evaluated to be ca. 20.999 m²/g, 0.111 cm³/g, and 0.892 nm, respectively. Magnetization curve indicated that saturation magnetization Ms for as-synthesized HM nanoparticles was calculated to be approximately 1.71 emu/g and revealed weakly ferromagnetic features at room temperature. In addition, HM nanoparticles exhibited noticeable light absorption performance for potential applications in many fields such as electronics, optics, and catalysis. Hence, synthesis of HM nanoparticles via microwave-assisted reduction technology provides an effective way for utilizing FSR and easing environmental burden. Full article

Nanotechnology, specifically magnetic nanoparticles (MNPs), is revolutionizing cancer treatment. Magnetic hyperthermia is a treatment that, using MNPs, can selectively kill cancer cells without causing damage to the surrounding tissues. Background/Objectives: This work aimed to analyze how the synthesis conditions, namely, how the pH of the reaction can influence the magnetic properties of Fe₃O₄ nanoparticles for magnetic hyperthermia, using the hydrothermal synthesis. Methods: For the hydrothermal synthesis, FeCl₃·6H₂O and FeCl₂·4H₂O were mixed with different quantities of NaOH to adjust the pH. After obtaining a black precipitate, the samples were placed in an autoclave at 200 °C for 60 h, followed by a washing and drying phase. The obtained MNPs were analyzed using X-Ray Diffraction (XRD), Transmission Electron Microscopy, a Superconducting Quantum Interference Device, Specific Absorption Rate analysis, and cytotoxicity assays. Results: Different MNPs were analyzed (9.06 < pH < 12.75). The XRD results showed the presence of various iron oxide phases (magnetite, maghemite, and hematite), resulting from the oxidization of the iron phases present in the autoclave. In terms of the average particle size, it was verified that, by increasing the pH value, the size decreases (from 53.53 nm to 9.49 nm). Additionally, MNPs possess a superparamagnetic behaviour with high SAR values (above 69.3 W/g). Conclusions: It was found that the pH of the reaction can influence the size, morphology, magnetization, and thermal efficiency of the MNP. The MNP with the highest composition of Fe₃O₄ was synthesized with a pH of 12.75, with a cubic morphology and a SAR value of 92.7 ± 3.2 W/g. Full article

An aqueous leaf extract of Egeria densa was used to green-synthesize iron (II) and iron (III) oxide nanoparticles from ferrous sulphate and ferric chloride, respectively. The successful green synthesis of the nanoparticles was confirmed through UV–visible spectroscopy, and the colour of the mixtures changed from light-yellow to green-black and reddish-brown for FeO–NPs and Fe₂O₃–NPs, respectively. The morphological characteristics of the nanoparticles were determined using an X-ray diffractometer (XRD), a Fourier transform infrared spectrophotometer (FTIR), a transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDX). The UV–Vis spectrum of the FeO–NPs showed a sharp peak at 290 nm due to the surface plasmon resonance, while that of the Fe₂O₃–NPs showed a sharp peak at 300 nm. TEM analysis revealed that the FeO–NPs were oval to hexagonal in shape and were clustered together with an average size of 18.49 nm, while the Fe₂O₃-NPs were also oval to hexagonal in shape, but some were irregularly shaped, and they clustered together with an average size of 27.96 nm. EDX analysis showed the presence of elemental iron and oxygen in both types of nanoparticles, indicating that these nanoparticles were essentially present in oxide form. The XRD patterns of both the FeO–NPs and Fe₂O₃–NPs depicted that the nanoparticles produced were crystalline in nature and exhibited the rhombohedral crystal structure of hematite. The FT-IR spectra revealed that phenolic compounds were present on the surface of the nanoparticles and were responsible for reducing the iron salts into FeO–NPs and Fe₂O₃–NPs. Conclusively, this work demonstrated for the first time the ability of Elodea aqueous extract to synthesize iron-based nanoparticles from both iron (II) and iron (III) salts, highlighting its versatility as a green reducing and stabilizing agent. The dual-path synthesis approach provides new insights into the influence of the precursor oxidation state on nanoparticle formation, thereby expanding our understanding of plant-mediated nanoparticle production and offering a sustainable route for the fabrication of diverse iron oxide nanostructures. Furthermore, it provides a simple, cost-effective, and environmentally friendly method for the synthesis of the FeO–NPs and Fe₂O₃–NPs using Egeria densa. Full article

Recently, attention has shifted towards the green synthesis of nanoparticles using plant extracts rich in phytochemicals like phenols and flavonoids, offering an alternative method that avoids harmful chemicals and enables large-scale, low-cost production. This study introduces a straightforward and eco-friendly approach to synthesizing hematite α-Fe₂O₃ nanoparticles utilizing an aqueous extract of Musa paradisiaca. The variation in the calcination temperature resulted in the formation of nanoparticles presented as Fe₂O₃ (1), Fe₂O₃ (2), and Fe₂O₃ (3), obtained at 650, 750, and 900 °C for 4 h, respectively. This variation allowed for an investigation into the impact of different reaction temperatures on the structural and optical properties of the nanoparticles. Structural analysis was conducted using X-ray diffraction (XRD), while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to examine morphology. Optical properties were assessed via UV-vis spectroscopy, revealing a reduction in the energy band gap (from 2.5 to 1.87 eV), attributed to an increase in crystallite size resulting from longer calcination temperatures (650–900 °C). A biological assay was carried out to evaluate the antioxidant and anticancer potentials of the nanoparticles. Both Fe₂O₃ (1) and Fe₂O₃ (2) with IC₅₀ values of 46.84 and 46.14 µg/mL, respectively, showed similar antioxidant potentials, while peel extract exhibited the least activity with an IC₅₀ of 79.26 µg/mL. The nanoparticles, peels, and 5-FU (used as standard) showed a stronger inhibitory effect on the Human Embryonic Kidney (HEK) 293 cells compared to the HeLa cells. This implies that the HEK 293 cells might be more susceptible to the drug samples and a lower concentration might even be sufficient to achieve the inhibition of normal cell proliferation. These results indicate a better therapeutic window with a lesser inhibitory effect compared to standard drugs used as controls. Full article

Energy and environmental challenges are driving researchers to explore cost-effective and eco-friendly nanomaterial fabrication methods. In this study, Atmospheric Pressure Microplasma (AMP) was used to synthesize iron oxide nanoparticles at varying molar concentrations of ferrous sulfate (0.5 M, 1 M, and 1.5 M) under a 15 kV discharge voltage for 90 min. The X-ray diffraction (XRD) results confirmed the formation of mixed cubic and hexagonal phases of magnetite and hematite nanoparticles. The particle size, calculated using the Debye–Scherrer formula, ranged from 9 to 11 nm, depending on the precursor concentration. Scanning electron microscopy (SEM) images revealed spherical nanoparticles at 0.5 M, while agglomeration occurred at 1.5 M. The energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of iron and oxygen in the synthesized nanoparticles. Fourier-transform infrared (FTIR) and UV spectroscopy showed characteristic absorption bands of iron oxide. The impact of the particle size and lattice strain on the optical properties of the nanoparticles was also studied. Smaller nanoparticles exhibited an excellent specific capacitance (627) and a strong charge–discharge performance in a 3 M KOH solution, with a high energy density (67.72) and power density (2227). As photocatalysts, the nanoparticles demonstrated a 97.5% and 96.8% degradation efficiency against methylene blue (MB) and methyl orange (MO), respectively, with high rate constants. These results surpass previous reports. The enhanced electrochemical performance and photocatalytic activity are attributed to the high-quality iron oxide nanoparticles, showing an excellent cyclic stability, making them promising for supercapacitors and environmental remediation. Full article

Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode. Full article

Siderite (FeCO₃) is an iron-bearing carbonate mineral that is the most abundant sedimentary iron formation on Earth. The influence of time, temperature, and isomorphous impurities on the kinetics of siderite decomposition in air was studied using Mössbauer spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and the Transmission Electron Microscopy method. Two rock siderite samples were used for investigations, one containing a significant amount of magnesium. The siderite decomposition process begins at a temperature of 300 °C. In a sample containing practically no magnesium, complete decomposition occurs at a temperature of 450 °C, and in a sample with magnesium at a temperature of 500 °C. The annealing time does not affect the width of the temperature range where siderite decomposition occurs. Still, it affects the degree of siderite decomposition: the longer the annealing time, the greater the amount of siderite decomposition. The decomposition products of siderite annealed in air are iron oxides. In the sample containing practically no Mg, this oxide was mainly hematite, and in the sample containing magnesium, it was magnesioferrite. Iron oxides formed directly in siderite decomposition are poorly crystalline, and we can treat them as iron oxide nanoparticles. They maintain this form in a wide temperature range, especially in a magnesium-containing sample. The presence of this element significantly slows down the process of magnesioferrite crystallization. Full article

Nanoparticles of ZnFe₂O₄ and hematite with varied sizes and distributions were synthesized using the two-solvent method (cyclohexane, water) on SBA-15 silica batches. Calcination is performed in air at 700 °C (2 °C/min) with rapid quenching produced catalysts with distinct nanoparticle configurations, namely, internal zinc ferrite and external hematite. The choice of precursor was critical, and nitrate salts yielded only zinc ferrite nanoparticles, while chloride salts produced a mixture of hematite and zinc ferrite. The photocatalytic activity of these materials was evaluated under visible light irradiation from an LED lamp, using O₂ from air as an oxidizing agent without the addition of H₂O₂. Samples enriched with external hematite nanoparticles from chloride precursors achieved the highest activity, decomposing 30% of AMX in 225 min. In contrast, nitrate-derived samples with predominantly internal zinc ferrite nanoparticles exhibited lower catalytic activity. Characterization via TEM, XRD, N2 sorption, and Mössbauer spectroscopy confirmed the structural and magnetic properties of the nanoparticles. Mössbauer spectra, particularly at 12K and under a magnetic field, demonstrated the presence of hematite nanoparticles, distinguishing them from isolated Fe (III) cations. Zinc ferrite nanoparticles exhibited specific magnetic ordering, with Fe ions occupying tetrahedral and octahedral sites. The results demonstrate the critical role of nanoparticle, composition, and positioning in optimizing photocatalytic efficiency for water decomposition. Full article

An enormous quantity of titanium slag has caused not merely serious environment pollution, but also a huge waste of iron and sulfur resources. Hence, recycling iron and sulfur resources from titanium slag has recently been an urgent problem. Herein, hematite nanoparticles were fabricated through a pyrite reduction approach using as-received titanium slag as the iron source and pyrite as the reducing agent in an nitrogen atmosphere. The physicochemical properties of the hematite nanoparticles were analyzed using multiple techniques such as X-ray diffraction pattern, ultraviolet–visible spectrophotometry, and scanning electron microscopy. The best synthesis conditions for hematite nanoparticles were found at 550 °C for 30 min with the mass ratio of 14:1 for titanium slag and pyrite. The results demonstrated that hematite nanoparticles with an average particle diameter of 45 nm were nearly spherical in shape. The specific surface area, pore volume, and pore size estimated according to the BET method were 19.6 m²/g, 0.117 cm³/g, and 0.89 nm, respectively. Meanwhile, the fabricated hematite nanoparticles possessed weak ferromagnetic behavior and good absorbance in the wavelength range of 200 nm-600 nm, applied as a visible light responsive catalyst. Consequently, these results show that hematite nanoparticles formed by the pyrite reduction technique have a promising application prospect for magnetic material and photocatalysis. Full article

The separation of rare earth ions (RE³⁺) from aqueous solutions poses a significant challenge due to their similar chemical and physical characteristics. This study presents a method for synthesizing hematite nanoparticles (Fe₂O₃ NPs) through the high-temperature phase transition of natural pyrite for adsorbing RE³⁺ from mine wastewater. The characteristics of Fe₂O₃ NPs were studied using XRD, SEM, BET, XPS, FTIR, and Zeta potential. The optimal condition for RE³⁺ adsorption by Fe₂O₃ NPs was determined to be at pH 6.0 with an adsorption time of 60 min. The maximum adsorption capacities of Fe₂O₃ NPs for La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Dy³⁺, and Y³⁺ were 12.80, 14.02, 14.67, 15.52, 17.66, 19.16, 19.94, and 11.82 mg·g⁻¹, respectively. The experimental data fitted well with the Langmuir isotherm and pseudo-second-order models, suggesting that the adsorption process was dominated by monolayer chemisorption. Thermodynamic analysis revealed the endothermic nature of the adsorption process. At room temperature, the adsorption of RE³⁺ in most cases (La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, and Y³⁺) onto Fe₂O₃ NPs was non-spontaneous, except for the adsorption of Gd³⁺ and Dy³⁺, which was spontaneous. The higher separation selectivity of Fe₂O₃ NPs for Gd³⁺ and Dy³⁺ was confirmed by the separation factor. Moreover, Fe₂O₃ NPs exhibited excellent stability, with an RE³⁺ removal efficiency exceeding 94.70% after five adsorption–desorption cycles, demonstrating its potential for the recovery of RE³⁺ from mine wastewater. Full article

Toxoplasma gondii is an intracellular parasitic protozoan with a high infection rate in mammals, including humans, and birds. There is no effective vaccine, and treatment relies on antiparasitic drugs. However, existing antiprotozoal drugs have strong side effects and other problems; therefore, new treatment approaches are needed. Metal nanoparticles have attracted increased interest in the biomedical community in recent years because of their extremely high surface area to volume ratio and their unique reactivity that could be exploited for medicinal purposes. Previously, we confirmed the anti-Toxoplasma effects of gold, silver, and platinum nanoparticles, in a growth inhibition test. Here, we asked whether the anti-Toxoplasma effect could be confirmed with less expensive metal nanoparticles, specifically iron oxide nanoparticles (goethite and hematite). To improve the selective action of the nanoparticles, we modified the surface with l-tryptophan as our previous findings showed that the bio-modification of nanoparticles enhances their selectivity against T. gondii. Fourier-Transform Infrared Spectroscopy (FTIR) analysis confirmed the successful coating of the iron oxide nanoparticles with l-tryptophan. Subsequently, cytotoxicity and growth inhibition assays were performed. L-tryptophan-modified nanoparticles showed superior anti-Toxoplasma action compared to their naked nanoparticle counterparts. L-tryptophan enhanced the selective toxicity of the iron oxide nanoparticles toward T. gondii. The bio-modified nanoparticles did not exhibit detectable host cell toxicity in the effective anti-Toxoplasma doses. To elucidate whether reactive oxygen species contribute to the anti-Toxoplasma action of the bio-modified nanoparticles, we added Trolox antioxidant to the assay medium and found that Trolox appreciably reduced the nanoparticle-induced growth inhibition. Full article

This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. Characterization techniques, including microscopy and spectroscopy, analyze the sweet pepper extract-magnetic iron oxide nanoparticles. Antioxidant capacities against 2,2-diphenyl-1-picrylhydrazyl are assessed, incorporating nanoparticles into banana-based bioplastic for grape preservation. Microscopy reveals cubic and quasi-spherical structures, and spectroscopy confirms functional groups, including Fe–O bonds. X-ray diffraction identifies cubic and monoclinic magnetite with a monoclinic hematite presence. Sweet pepper extract exhibits 100% inhibitory activity in 20 min, while sweet pepper extract-magnetic iron oxide nanoparticles show an IC₅₀ of 128.1 µg/mL. Furthermore, these nanoparticles, stabilized with banana-based bioplastic, effectively preserve grapes, resulting in a 27.4% lower weight loss rate after 144 h compared to the control group (34.6%). This pioneering study encourages institutional research into the natural antioxidant properties of agro-waste sweet pepper combined with magnetic iron and other metal oxide nanoparticles, offering sustainable solutions for nanopackaging and food preservation. Current research focuses on refining experimental parameters and investigating diverse applications for sweet pepper extract-magnetic iron oxide nanoparticles in varied contexts. Full article

In this study, 3-dimensional molybdenum disulfide (MoS₂) structures, integrated with hematite (α-Fe₂O₃) nanoparticles, were fabricated under a convenient two-step hydrothermal route. The fabricated photocatalytic nanocomposites consist of well-arranged MoS₂ flakes, resembling spherical flower-like morphology, and the nanoparticulate α-Fe₂O₃ structures decorate the 3D network. By raising the α-Fe₂O₃ weight ratio, the composites’ specific surface area and morphology were not affected, regardless of the partial cover of the cavities for higher hematite content. Moreover, the crystallinity examination with XRD, Raman, and FTIR techniques revealed that the precursor reagents were fully transformed to well-crystalized MoS₂ and Fe₂O₃ composites of high purity, as no organic or inorganic residues could be detected. The photocatalytic oxidation and reduction performance of these composites was evaluated against the tetracycline pharmaceutical and the industrial pollutant hexavalent chromium, respectively. The improvement in the removal efficiencies demonstrates that the superior photoactivity originates from the high crystallinity and homogeneity of the composite, in combination with the enhanced charge carriers’ separation in the semiconductors’ interface. Full article