Search Results (87)

Magnetic nanoparticles represent the next-generation drug delivery systems, enabling drug targeting to specific organs without adverse effects on the body and with a controlled release rate. Their strengths are represented by biocompatibility, low cost, and easy drug loading; some drawbacks are aggregation and poor stability in biological media. In the present work, we synthesized magnetic core–shell structures with a magnetite core coated with layered double hydroxides (LDHs) based on Mg²⁺ or Zn²⁺ and Al³⁺ ions and loaded with meloxicam, a poorly water-soluble anti-inflammatory drug. Several syntheses have been attempted to obtain iron oxides based on the only magnetite phase. The combined use of different characterization techniques allowed us to reveal that the best product, showing the crucial room temperature superparamagnetism and a good level of compositional uniformity, was obtained from co-precipitation in nitrogen flow. The next LDH coating was successful, even if the hybrids showed the occurrence of aggregation. The drug was mainly adsorbed onto the LDH surfaces, as shown by the X-ray diffraction and Infrared Spectroscopy techniques. The loaded meloxicam amount was low, but the subsequent release into simulated body fluid could be prolonged for 4 days. Our study provides a proof of concept about the importance of a thorough characterization of the nanocomposite hybrids and their possible use for tricky drugs, such as those of class II of the Biopharmaceutical Classification System. Full article

Green nephrite of the serpentine-replacement type often consists predominantly of the actinolite–tremolite series, with minor minerals such as uvarovite, grossular, chromite, magnetite, diopside, zircon, apatite, epidote, graphite, and phlogopite, which commonly reduce gem quality. However, nephrite from the Polar deposit in Canada represents an exception. This material consists mainly of the actinolite–tremolite series, with minor Cr-bearing grossular garnet and chromite. Actinolite–tremolite occurs as aggregates of fine fibers without obvious orientations, surrounding centimeter-scale, vivid green, berry-shaped garnet aggregates, within which residual chromite islands were observed. This vivid green color occurs over extensive areas, enhancing rather than reducing gem quality. Garnets contain 0.53–0.90 Cr apfu with lower Fe content, whereas amphiboles exhibit 0.01–0.06 Cr apfu and 0.46–0.87 Fe²⁺ apfu, values significantly higher than that observed in the adjacent grossular. Garnet is a minor mineral occasionally existing in green nephrite; however, the discovery of berry-shaped, vivid green garnet has only been reported at this location. The fine-grained, Al-rich garnet aggregates with relatively low Cr and Fe content suggest that a continuous replacement reaction potentially occurred. A more multifaceted value assessment framework that emphasizes the uniqueness of artistic expression and cultural connotation are proposed. Full article

Nanoparticles of ferrimagnetic magnetite (Fe₃O₄) are cornerstones of modern nanoscience and technology, primarily due to their superparamagnetic behavior. Beyond traditional applications in magnetorheology and magnetic hyperthermia, these materials are increasingly vital in fields like active matter, where precise surface fine-tuning is crucial. While coating isotropic, quasi-spherical magnetite nanoparticles with silica is a well-established and versatile route towards functionalization, transferring this achievement to nanorod systems remains a significant challenge. Successful coating of these high-aspect-ratio geometries would allow to exploit the direction-dependent properties and increased magnetic anisotropies. However, current literature largely focuses on polycrystalline rods composed of small, clustered subunits, which limits their magnetic potential. This work describes a breakthrough in the homogeneous silica coating and stabilization of monocrystalline magnetite nanorods. We demonstrate that the superior magnetic properties of these “naked” monocrystalline rods induce strong dipole-dipole interactions, which trigger aggregation and typically prevent the isolation of individual and homogeneously coated core-shell nanoparticles. By investigating the specific mechanisms of this aggregation, we established a robust coating procedure that yields the desired isolated particles. Critically, we show that the magnetite nanorods retain their monocrystalline integrity within the silica shell, thereby preserving the enhanced magnetic properties of the original nanocrystals. Full article

Direct hydroxylation of benzene to phenol using hydrogen peroxide is a cornerstone of sustainable green chemistry. This paper presents the results of a stability study of an iron-containing mordenite catalyst in the liquid-phase hydroxylation of benzene to phenol with a 30% aqueous hydrogen peroxide solution. The study utilizes a combination of catalytic activity measurements, dynamic light scattering (DLS), and electron paramagnetic resonance (EPR) spectra. The system is initially shown to exhibit high phenol selectivity; however, over time, DLS measurements indicate aggregation of the catalyst particles with an increase in the average particle diameter from 1.8 to 2.6 μm and the formation of byproducts–dihydroxybenzenes. Iron is present predominantly as magnetite nanoparticles (Fe₃O₄) ~10 nm in diameter, stabilized on the outer surface of mordenite, with minor leaching (<10%) due to the formation of iron ion complexes with ascorbic acid as a result of the latter’s interaction with magnetite particles. Using a thermodynamic approach based on the Ulich formalism (first and second approximations), it is shown that the reaction of benzene hydroxylation H₂O₂ in the liquid phase is thermodynamically quite favorable (ΔG° = −(289–292) kJ·mol⁻¹ in the range of 293–343 K, K = 1044–1052). It is shown that ascorbic acid acts as a redox mediator (reducing Fe³⁺ to Fe²⁺) and a regulator of the catalytic medium activity. The stability of the catalytic system is examined in terms of the Lyapunov criterion: it is shown that the total Gibbs free energy (including the surface contribution) can be considered as a Lyapunov functional describing the evolution of the system toward a steady state. Ultrasonic (US) treatment of the catalytic system is shown to redisperse aggregated particles and restore its activity. It is established that the catalytic activity is due to nanosized Fe₃O₄ particles, which react with H₂O₂ to form hydroxyl radicals responsible for the selective hydroxylation of benzene to phenol. Full article

Severe asphalt ageing and the difficulty in dispersing agglomerated particles within reclaimed asphalt pavement (RAP) hinder the uniform blending of virgin and aged mineral aggregates during plant-mixed hot recycling, compromising the durability of the recycled asphalt mixture. To accurately quantify the degree of blending between virgin and aged aggregate during thermal recycling and to optimise the mix design and mixing process for thermally recycled asphalt mixtures, a test method has been proposed. This method comprises key steps, including the preparation of asphalt mixtures, separation of virgin and aged materials, separation of the binder from aggregate, and calculation of the blending degree. It analyses the impact of varying mixing conditions on the blending degree of virgin and aged aggregate during the thermal recycling process. The results indicate that complete homogenization of virgin and aged aggregates during mixing is unattainable, with blending efficiency ranging from 40% to 60%. Increasing the amount of RAP has a negligible effect on blending efficiency. Appropriate increases in the amount of rejuvenating agent, mixing temperature, mixing time, and asphalt content enhance blending efficiency by 10% to 30%. The mixing sequence where RAP is first blended with virgin aggregate before incorporating virgin asphalt further enhances the blending efficiency of virgin and aged aggregates by approximately 20%. However, mixing temperatures exceeding 160 °C and mixing times exceeding 270 s caused secondary ageing of the asphalt, adversely affecting the blending degree of virgin and aged aggregates. Full article

Growing concern over nanoplastics as emerging pollutants calls for effective treatment methods, with advanced oxidation processes (AOPs) showing strong potential for their degradation. This study examines the interaction between polyethylene terephthalate nanoplastics (PET-NPs) and magnetite nanoparticles (MNPs) in a heterogeneous Fenton-like system, focusing on colloidal behavior, hydroxyl radicals (^●OH) generation, and potential degradation pathways. Zeta potential (ZP) and particle diameter measurements were used to characterize nanoparticle dispersion and aggregation mechanisms over a pH range of 3–9.5. The results revealed a pronounced pH-dependent stability, with MNPs exhibiting larger hydrodynamic diameters (283 nm) and lower stability at pH 3 (ZP: −9.8 mV) compared with neutral or alkaline conditions (189 nm; ZP: −44 to −42 mV). PET-NPs exhibited minimal agglomeration at a pH of 9.5 (ZP: −25.6 mV). Unlike conventional Fenton systems, ^●OH production peaked at pH 7–9.5 (0.3–0.35 μM), attributed to preserved Fe²⁺ sites and reduced particle agglomeration. Although PET-NPs resisted oxidative degradation, their aggregation with MNPs enabled magnetic recovery (46% efficiency at pH 3) through charge screening, Fe³⁺/Fe²⁺ bridging, and hydrophobic interactions. These findings highlight MNPs’ potential for sustainable nanoplastic separation and emphasize the need for optimized catalysts to enhance ^●OH-driven degradation. Overall, this work advances understanding of nanoplastic–magnetite interactions and offers insights into AOP applications. Full article

The growing demand for radiation-shielded infrastructure highlights the need for materials that balance shielding performance with environmental and economic sustainability. Heavyweight self-compacting concretes (HWSCC), commonly produced with barite (BaSO₄) or magnetite (Fe₃O₄) aggregates, lack systematic life cycle comparisons. The aim of this study is to systematically compare barite- and magnetite-based HWSCC in terms of life cycle environmental impacts, life cycle cost, functional performance (strength and shielding), and end-of-life circularity, in order to identify the more sustainable and cost-effective material for radiation shielding infrastructure. This study applies cradle-to-grave life cycle assessment (LCA) and life cycle cost analysis (LCC), in accordance with ISO 14040/14044 and ISO 15686-5, to evaluate barite- and magnetite-based HWSCC. Results show that magnetite concrete reduces global warming potential by 19% eutrophication by 24%, and fossil resource depletion by 23%, while lowering life cycle costs by ~23%. Both concretes achieve comparable compressive strength (~48 MPa) and shielding efficiency (µ ≈ 0.28–0.30 cm⁻¹), meeting NCRP 147 and IAEA SRS-47 standards. These findings demonstrate that magnetite-based HWSCC offers a more sustainable, cost-effective, and ethically sourced alternative for radiation shielding in healthcare, nuclear, and industrial applications. In addition, the scientific significance of this work lies in establishing a transferable methodological framework that combines LCA, LCC, and performance-normalized indicators. This enables scientists and practitioners worldwide to benchmark heavyweight concretes consistently and to adapt sustainability-informed material choices to their own regional contexts. Full article

We report here, for the first time on the Nubian Shield, the western half of the Arabian–Nubian Shield (ANS), pegmatite-hosted pockets with a unique mineralogy, including pyroxmangite. It represents the second discovery on the ANS, where the first one was at Jabal Aja on the Arabian Shield, the eastern half of the ANS. One of the most remarkable aspects of pyroxmangite is its rarity and the potential economic value of its use in jewelry and decorative applications. Pegmatites are associated with A-type granites of the Gabal El-Bakriya intrusion (GEBI), Eastern Desert, Egypt. Mineralized pegmatites occur at the margin of the alkali-feldspar granite and exhibit gradational contacts with the host rocks. The pegmatites were emplaced as plugs and dikes within the intrusion and along its periphery. Pyroxmangite appears as coarse-grained, massive black aggregates or as disseminated crystals. The pegmatites are composed of K-feldspars and quartz, with subordinate amounts of albite, micas, and mafic minerals. Accessory phases include monazite-(Ce), zircon, fergusonite, xenotime, fluorite, pyrochlore, allanite, thorite, bastnäsite, samarskite, cassiterite, beryl, and pyrochlore. Pyroxmangite-bearing assemblages consist essentially of pyroxmangite and garnet, with accessory pyrochroite, quartz, zircon, magnetite, and fluorite. Geochemically, the pegmatites are highly evolved, with elevated SiO₂ content (76.51–80.69 wt.%) and variable concentrations of trace elements. They show significant enrichment in Nb (Nb > Ta), Y, REE, Zr, Th, U, and F, consistent with NYF-type pegmatites. REE contents range from 173.94 to 518.21 ppm, reflecting diverse accessory mineral assemblages. Tectonically, the pegmatites crystallized in a post-collisional setting, representing a late-stage differentiate of the A-type GEBI magma. Mineralization is concentrated in the apical and marginal zones of the granitic cupola and is dominated by barite, fluorite, Nb-Ta oxides, REE minerals, and uranium-bearing phases. The highly evolved granites, greisens, pegmatites, and quartz-fluorite veins of the GEBI have a high economic potential, deserving further exploration. Full article

In this study, the feasibility of converting iron-bearing tailings from urban steel scrap recycling to value-added direct reduced iron (DRI) via magnetic separation followed by hydrogen reduction under microwave irradiation was investigated, with an emphasis on the effect of reduction temperature. The experimental results showed that by magnetic separation, the tailings sample with an iron content of 15.42 wt% could transit to a high-grade magnetic concentrate with an iron content of 60.04 wt% and good microwave absorption capability, as revealed by its short microwave penetration depth (D_p). After hydrogen reduction under microwave irradiation, the main iron-bearing phases, including magnetite, hematite, limonite, and martite, had stepwise deoxidation into metallic iron. As the reduction temperature increased from 750 °C to 1050 °C, the total iron content (TFe), reduction degree and iron metallization degree of the product increased rapidly and then became stable due to difficult reduction of FeO. As the reduction process proceeded, the dispersed iron particles gradually aggregated. At the optimum temperature of 950 °C, the reduction degree and iron metallization degree reached 90.10% and 88.71%, respectively. Meanwhile, the pore size, microporous volume, and specific surface area of the product were 1.943 nm, 1.767 × 10⁻⁵ cm³/g, and 0.3961 m²/g, respectively. The saturation magnetization (M_S) and coercivity (H_C) of the product remained 170.94 emu/g and 46.25 Oe, respectively. The product can act as a potential feedstock for electric arc furnace (EAF) steelmaking. Full article

Glutamate, the primary excitatory neurotransmitter in the central nervous system, plays a pivotal role in synaptic signaling, learning, and memory. Abnormal glutamate levels are implicated in various neurological disorders, including epilepsy, Alzheimer’s disease, and ischemic stroke. Despite the utility of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in diagnosing such conditions, the development of effective glutamate-sensitive contrast agents remains a challenge. In this study, we present ultrasmall, citric acid-coated superparamagnetic iron oxide nanoparticles (CA-SPIONs) as highly selective and sensitive MRS probes for glutamate detection. These 5 nm magnetite CA-SPIONs exhibit a stable dispersion in physiological buffers and undergo aggregation in the presence of glutamate, significantly enhancing the T₂ MRS contrast power. At physiological glutamate levels, the CA-SPIONs yielded a pronounced signal change ratio of nearly 60%, while showing a negligible response to other neurotransmitters such as GABA and dopamine. Computational simulations confirmed the mechanism of glutamate-mediated aggregation and its impact on transversal relaxation rates and relaxivities. The sensitivity and selectivity of CA-SPIONs underscore their potential as eco-friendly, iron-based alternatives for future neurological sensing applications targeting glutamatergic dysfunction. Full article

High temperatures can induce a range of physical and chemical alterations in radiation-protective concrete, potentially compromising its strength and significantly diminishing its radiation shielding capabilities. Therefore, it is very important to study the high temperature performance of radiation-proof concrete to ensure its safety and stability in extreme environment. In this study, the magnetite–serpentine radiation-proof concrete is designed with magnetite as coarse aggregate, serpentine as fine aggregate, and Portland cement and granulated blast furnace slag as mixture. The apparent characteristics, mass loss, ultrasonic pulse velocity, mechanical properties, shielding performance, and correlation of this concrete were analyzed through experiments. The results show that the damage degree and relative wave velocity have a good correlation in evaluating the relative mass loss, linear attenuation coefficient, compressive strength, and tensile strength after high temperatures. The compressive strength at 800 °C is 12.2 MPa and the splitting tensile strength is 0.48 MPa; the linear attenuation coefficient of specimen at 800 °C is reduced to 80.9% of that at normal temperature. Meanwhile, penetrating cracks appeared at 600 °C and spalling phenomenon appeared at 800 °C, and better thermal stability and favorable mechanical properties and shielding performance also occurred; thus, suitable radioactive and high temperature environment was determined. The results could provide scientific guidance for nondestructive testing and performance evaluation of shielding structure materials. Full article

We studied the chemical composition and morphostructural features of micron and submicron-sized particles of native gold in apocarbonate tremolite–diopside skarns of the Ryabinovoye deposit located on the southeastern margin of the Aldan Shield (Far East, Russia). Polished sections of lump ore samples containing native gold were analyzed by scanning electron microscopy in combination with X-ray microanalysis using different modes of visualization and X-ray diffraction methods. Gold particles, clearly visible after etching the surface of some polished sections with acids and partial or complete dissolution of some host minerals, were also examined. Native gold from the studied deposit is of high fineness (above 970‰) and contains (in wt.%) <1.59 Ag and less commonly <0.37 Cu and <0.15 Zn. Native gold is found intergrown with tremolite, diopside, and other magnesian silicates, as well as calcite, fluorite, magnetite, and sphalerite. Rare microinclusions of pyrrhotite, galena, and clinohumite are present in gold grains. It was found that native gold inherits the morphology of tremolite crystals and aggregates, which is determined by the size and shape of the voids bounded by its crystals. Gold localized in the intercrystalline spaces and in the zones of conjugation with remobilized calcite has irregular, lumpy shapes and partially or completely faceted grains with a dense structure. The nature of the localization and distribution of native gold in ores is due to the crystallization of the tremolite component of skarns. Apparently, the processes of gold accumulation are caused by the thermal activation of solid-phase differentiation of the substance of carbonate rocks, in which the processes of destruction of the original minerals and collective recrystallization play a significant role. It is likely that at some gold skarn deposits, carbonate rocks could be the source of gold. Data on the morphology and sizes of native gold segregations, as well as on the intergrown minerals, can be used to improve gold extraction technologies. A specific group of minerals intergrown with native gold in gold skarn deposits can be used as a diagnostic feature in the primary search for placer gold. The obtained results will help to better understand the formation of native gold in apocarbonate tremolite–diopside skarns. Full article

Adjuvant chemotherapy is a critical regime in cancer treatment. The magnetic targeted drug delivery system (MTDDS) can selectively aggregate chemotherapy agents at the target areas, which has attracted great attention due to its safety, high efficiency, and minimal side effects on the human body. It would be ideal to establish a tissue engineering scaffold that can not only reconstruct the defect from the surgical tumor removal, but also serve as a magnetic station to attract MTDDS to the local site to enhance the targeted drug delivery. The current study constructed polycaprolactone magnetic tissue engineering scaffolds with various micrometer-sized magnets. The degradation properties of the scaffolds were assessed in simulated body fluid (SBF), and primary mouse bone marrow stromal cells were used to evaluate the biocompatibility of the scaffolds to osteoblast differentiations. The scaffolds were further examined by implantation to an air pouch model on the back of BALB/c mice. The in vitro data suggested that up to 40% of micron-sized magnetite can be used to formulate porous polycaprolactone (PCL) scaffolds with comparable biocompatibility to the PCL-alone scaffold. A mouse study revealed that the intro-peritoneal injected fluorescence-magnetic particles were collectedly enriched in the mouse air pouch tissues containing the 20% magnetic/PCL scaffolds. Histological assessment and the real-time PCR results of the air pouches confirmed the benign biocompatibility of the implanted magnetic scaffolds. Full article

Radiation-shielding concrete, widely used in protective structures because of its effective shielding properties, employs magnetite aggregates to achieve higher compressive strength than conventional concrete. However, prolonged exposure to high temperatures leads to mechanical degradation. This study investigates the thermal evolution of magnetite concrete under microwave heating across varying temperatures (38–800 °C). A microwave oven was utilized for heating, and COMSOL Multiphysics was employed to establish an electromagnetic-thermal-mechanical coupled model, analyzing surface characteristics, temperature distribution, stress-strain behavior, and residual compressive strength. Results indicate that internal temperatures exceed surface temperatures during microwave heating, with a maximum temperature difference surpassing 150 °C at 800 °C. Compressive stresses predominantly arise in the mortar, while tensile stresses concentrate in aggregates and the interface transition zone, causing stress concentration. Mortar exhibits greater deformation than aggregates as temperatures increase. Simulated and experimental residual compressive strengths show strong agreement, with a maximum deviation of 7.58%. The most rapid mechanical deterioration occurs at 450–600 °C, marked by a residual compressive strength decline of 0.07 MPa/°C and the formation of penetrating cracks. Full article

Based on the magnetic sensitivity of Fe₃O₄ in various fields, we aimed to propose a one-step solvothermal process for the synthesis of single-phase Fe₃O₄ induced by the reaction medium and urea, avoiding high-temperature reduction in H₂ or N₂ atmospheres. Feasibility was tested with purified water (H₂O), methyl alcohol (MA), ethyl alcohol (EA), and ethylene glycol (EG) as reaction media. The findings indicated that the solvothermal reaction system utilizing EA was more effective for the synthesis of cubic magnetic Fe₃O₄. Optimal conditions for synthesizing pure Fe₃O₄ were obtained by optimizing the urea amount and solvothermal reaction parameters. The optimal formulation consisted of 10 mmol of FeCl₃, 80 mmol of urea, and 60 mL of EA subjected to a solvothermal process at 200 °C for 12 h. The resulting Fe₃O₄ (magnetite, cubic) exhibited commendable crystallization with a morphology of acicular aggregates and displayed excellent magnetic sensitivity properties with a magnetization of 92.2 emu/g at 15,000 Oe. The photocatalytic degradation behaviors of the resulting Fe₃O₄ to Methyl Orange, Orange G, and Acid Red 37 azo dyes and the repeated degradation performance of Methyl Orange dye were investigated. Nearly complete degradation of Methyl Orange dye occurred after 2.0 h of photocatalytic reaction, while Orange G and Acid Red 37 dyes achieved similar results after 3.5 and 4.5 h, respectively. The exploration strategy in this work for synthesizing magnetic Fe₃O₄ can be applied to design and fabricate other metal oxides or composites, potentially resulting in novel discoveries in morphology or performance. Full article