Search Results (281)

Co_0.95R_0.05Fe₂O₄ nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic Fd-3m structure. XPS shows the presence of Gd³⁺ and Ho³⁺ ions. The spin–orbit splitting of about 15.4 eV observed in Co 2p core-level spectra is an indication that Co is predominantly present as Co³⁺ state, while the satellite structures located at about 6 eV higher energies than the main lines confirm the existence of divalent Co in Co_0.95R_0.05Fe₂O₄. The positions of the Co 3s and Fe 3s main peaks obtained by curve fitting and the exchange splitting obtained values for Co 3s and Fe 3s levels point to the high Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ ratios in both samples. The saturation magnetizations are smaller for the doped samples compared to the pristine ones. For theoretical magnetization calculation, we have considered that the heavy rare earths are in octahedral sites and their magnetic moments are aligned antiparallelly with 3d transition magnetic moments. ZFC-FC curves shows that some nanoparticles remain superparamagnetic, while the rest are ferrimagnetic, ordered at room temperature, and showing interparticle interactions. The M_S/Ms ratio at room temperature is below 0.5, indicating the predominance of magnetostatic interactions. Full article

Co_0.95R_0.05Fe₂O₄ nanoparticles with R = La, Pr, Nd, Sm, and Eu were synthesized via an environmentally friendly sol–gel method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and magnetic measurements. All compounds were found to be single phases adopting a cubic Fd-3m structure. EDS analysis confirmed the presence of Co, Fe, R, and oxygen in all cases. The XPS measurements reveal that the Co 2p core-level spectra are characteristic for Co³⁺ ions, as indicated by the 2p_3/2 and 2p_1/2 binding energies and spin–orbit splitting values. The analysis of the Fe 2p core-level spectra reveals the presence of both Fe³⁺ and Fe²⁺ ions in the investigated samples. The doped samples exhibit lower saturation magnetizations than the pristine sample. Very good agreement with the saturation magnetization values was obtained if we assumed that the light rare-earth ions occupy octahedral sites and their magnetic moments align parallel to those of the 3d transition metal ions. The ZFC-FC curves indicate that some nanoparticles remain superparamagnetic, while others exhibit ferrimagnetic ordering at room temperature, suggesting the presence of interparticle interactions. The M_r/M_s ratio at room temperature reflects the dominance of magnetostatic interactions. Full article

In the present study, we synthesized fluorocarbon-coated cobalt ferrite (CoFe₂O₄) magnetic nanoparticles using alkoxysilanes such as trimethoxy(3,3,3-trifluoropropyl)silane (TFPTMS), trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane (NFHTMS), and triethoxy(1H,1H,2H,2H-perfluorodecyl)silane (PFDTES). The synthesized nanoparticles were characterized by various techniques, including X-ray diffractometry (XRD), transmission electron microscopy (TEM/HRTEM/EDXS), Fourier transform infrared spectroscopy (FTIR), specific surface area measurements (BET), and magnetometry (VSM). To understand their surface characteristics, contact angle (CA) measurements were carried out, providing valuable insights into their hydrophobic properties. Among the samples of CoFe₂O₄ coated with fluoroalkoxysilanes, those with PFDTES surface coating had the highest water contact angle of 159.2°, indicating their superhydrophobic character. The potential of the prepared fluoroalkoxysilane-coated CoFe₂O₄ nanoparticles for the removal of waste low-SAPS synthetic engine oil from a model aqueous solution was evaluated based on three key parameters: adsorption efficiency (%), adsorption capacity (mg/g), and desorption efficiency (%). All synthesized CoFe₂O₄ samples coated with fluoroalkoxysilane showed high oil adsorption efficiency, ranging from 87% to 98%. The average oil adsorption capacity for the samples was as follows: F₃-SiO₂@CoFe₂O₄ (3.1 g of oil/g of adsorbent) > F₉-SiO₂@CoFe₂O₄ (2.7 g of oil/g of adsorbent) > F₁₇-SiO₂@CoFe₂O₄ (1.5 g of oil/g of adsorbent) as a result of increasing oleophobicity with increasing fluorocarbon chain length. The desorption results, which showed 77–97% oil recovery, highlighted the possibility of reusing the adsorbents in multiple adsorption/desorption cycles. Full article

This study reports the synthesis and characterization of Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles using a co-precipitation method. In this approach, metal ions are precipitated in the presence of a stabilizing agent, which is a common and effective method for nanoparticle preparation. The microstructure and magnetic properties were studied after calcination at 600 °C and heat treatment at 1000 °C. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a single-phase spinel structure. The average crystallite size, calculated using the (311) diffraction peak and the Scherrer equation, ranged from 13 to 19 nm. Scanning electron microscopy (SEM) showed that the nanoparticles had a spherical morphology. Thermogravimetric and differential thermal analysis (TG-DTA) revealed a three-step weight loss process. Magnetic measurements, including remanent magnetization, saturation magnetization, and coercivity, were performed using a vibrating sample magnetometer (VSM) at room temperature. The replacement of Ni²⁺ with Co²⁺ enhanced the magnetic properties, resulting in increased magnetic moment and anisotropy. These effects are attributed to changes in cation distribution, exchange interactions, surface effects, and magnetocrystalline anisotropy. Overall, Co²⁺ doping improved the magnetic behavior of nickel ferrite, indicating its potential for application in memory devices and magnetic recording media. Full article

The removal of heavy metals from industrial wastewater remains a major environmental challenge, demanding efficient, sustainable solutions. This study explores the combined use of Chlorella vulgaris and amine-functionalized magnesium ferrite (MgFe₂O₄-NH₂) nanoparticles to remove cobalt ions from battery effluents. The research aims to explore the capacity of C. vulgaris to adsorb heavy metals, followed by their separation using magnetic nanoparticles. Cobalt adsorption by C. vulgaris was facilitated through the interaction of metal ions on the cell wall, achieving a removal efficiency of 96.44% within 30 min, which increased to 98.78% over 10 h. Amine-functionalized MgFe₂O₄ nanoparticles, synthesized and characterized using HRTEM, FTIR, and VSM, displayed high surface reactivity due to the presence of -NH₂ and -OH groups. At neutral pH, zeta potential measurements revealed a slightly negative charge (−5.6 ± 4.3 mV), while protonation at lower pH levels enhanced electrostatic interactions with the negatively charged algal biomass. Magnetic separation of the cobalt-adsorbed biomass achieved efficiencies ranging from 94.9% to 99.2% within 60 s, significantly outperforming conventional sedimentation methods. SEM and FTIR analyses confirmed the binding of nanoparticles to algal cell walls. The even distribution of MgFe₂O₄ nanoparticles on algal surfaces was further validated by TEM imaging, and the strong magnetic properties of the nanoparticles enabled rapid and efficient separation under an external magnetic field. Full article

In this study, praseodymium-doped cobalt ferrite nanoparticles (CoFe_2−yPr_yO₄, y = 0–0.2) were synthesized via sol-gel auto-combustion and systematically characterized to assess their structural, morphological, magnetic, and biological properties. X-ray diffraction (XRD) confirmed single-phase cubic cobalt ferrite formation for samples with y ≤ 0.05 and the emergence of a secondary orthorhombic PrFeO₃ phase at higher dopant concentrations. FTIR spectroscopy identified characteristic metal–oxygen vibrations and revealed a progressive shift of absorption bands with increasing praseodymium (Pr) content. Vibrating sample magnetometry (VSM) demonstrated a gradual decline in saturation (Ms) and remanent (Mr) magnetization with Pr doping, an effect further intensified by cyclodextrin surface coating. TEM analyses revealed a particle size increase correlated with dopant level, while SEM images displayed a porous morphology typical of combustion-synthesized ferrites. In vitro cell viability assays showed minimal toxicity in normal human keratinocytes (HaCaT), while significant antiproliferative activity was observed against human cancer cell lines A375 (melanoma), MCF-7 (breast adenocarcinoma), and HT-29 (colorectal adenocarcinoma), particularly in Pr 6-CD and Pr 7-CD samples. These findings suggest that Pr substitution and cyclodextrin coating can effectively modulate the physicochemical and anticancer properties of cobalt ferrite nanoparticles, making them promising candidates for future biomedical applications. Full article

Background/Objectives: Non-surgical neutering strategies have long been pursued for male animals. A previous study from our group showed that magnetic nanoparticle hyperthermia (MNH) applied directly to the testicles is a promising non-surgical sterilization method for male animals, causing testicular atrophy and complete disappearance of seminiferous tubules by the end of a 56 day observation. This long-term study was conducted to verify the long-term efficacy and safety of the method. Methods: Wistar rats treated with testicular MNH received an intratesticular injection of a magnetic fluid composed of manganese-ferrite nanoparticles functionalized with citrate (MnFe₂O₄-citrate) and were subsequently subjected to an alternating magnetic field. Reproductive parameters and animal health were evaluated by blood tests and abdominal ultrasound for 12 months. Results: All MNH-treated animals presented testicular degeneration and atrophy, together with severely reduced or undetectable serum testosterone levels. By the end of the experiment, all but two animals had no identifiable gonads. The only two animals still displaying gonadal-like structures were azoospermic, and histopathology revealed the remaining tissue was non-functional. The procedure was well-tolerated and MNH-treated animals presented no long-term side effects. Hemogram, ALT, AST, urea and creatinine levels were within the normal parameters for Wistar rats over the 12 month period. The liver, spleen, kidneys and lungs had normal structures as revealed by abdominal ultrasound and histopathological exams, with no nanoparticle accumulation in the organs over the long term. Conclusions: In conclusion, testicular MNH caused irreversible infertility in rats in a single application, with no adverse effects on general animal health. Full article

Magnetoelectric composites enable strain-mediated coupling between magnetic and electric fields, supporting applications in sensors, actuators, and tunable devices. This study presents a finite element modeling framework for simulating the direct magnetoelectric effect in core–shell and layered nanocomposites fabricated by material jetting (inkjet printing). The model incorporates nonlinear magnetostrictive behavior of cobalt ferrite nanoparticles and size-dependent piezoelectric properties of barium titanate, allowing efficient simulation of complex interfacial strain transfer. Results show a strong dependence of coupling on field orientation, particle arrangement, and interfacial geometry. Simulations of printed droplet geometries, including coffee ring droplet morphologies, reveal enhanced performance through increased surface area and directional alignment. These findings highlight the potential of material jetting for customizable, high-performance magnetoelectric devices and provide a foundation for simulation-guided design. Full article

The heat generation characteristics of magnetic nanoparticles (NPs) induced by an alternating magnetic field (AMF) while simultaneously exposed to a DC magnetic field are crucial for the clinical application of magnetic fluid hyperthermia integrated with magnetic particle imaging. In this study, we investigated the dependence of the specific absorption rate (SAR) of magnetite and cobalt (Co) ferrite NP suspensions on a static transverse DC magnetic field under an applied AMF. The results showed that the SAR of Co ferrite NPs remained unaffected by the DC magnetic field, whereas that of magnetite NPs gradually decreased as the DC magnetic field increased. Furthermore, the SAR of magnetite NPs dispersed in high-viscosity solvents was somewhat lower than that of particles dispersed in water, while the SAR of Co ferrite NPs was significantly reduced. These findings can be explained by differences in the Néel relaxation time, which arise from variations in magnetic anisotropy. Full article

In this study, copper ferrite nanoparticles, a type of ferrimagnetic spinel ferrite, were synthesized using the sol-gel auto-combustion method with three different fuels: citric acid, urea, and ethylene glycol. The crystal structures of the synthesized samples were analyzed using X-ray diffraction (XRD), and the growth of secondary phases like Fe₂O₃ and CuO for samples prepared with urea and ethylene glycol indicated the presence of impurities. Additionally, we observed that the particle size varied significantly with the type of fuel, being the smallest for citric acid and the largest for urea. The electrical and magnetic properties showed strong correlations with the particle size and the presence of impurities. In particular, the optical band gap values, derived from UV-Vis spectroscopy, varied significantly with the choice of fuel, ranging from 2.06 to 3.75 eV. The highest band gap of 3.75 eV was observed in samples synthesized with citric acid. Magnetic properties were measured using a vibrating sample magnetometer (VSM), and it was found that the copper ferrite synthesized with citric acid exhibited the highest values of magnetic saturation and coercivity. These findings demonstrate that the choice of fuel during the synthesis process has substantial impacts on the structural, optical, and magnetic properties of CuFe₂O₄ nanoparticles. Full article

Two-layered structures consisting of piezopolymer and magnetic elastomer were investigated as magnetoelectric material. Three types of magnetic elastomer based on cobalt ferrite (CoFe₂O₄) and Ni- or Zn-substituted CoFe₂O₄ nanoparticles were used as magnetically sensitive layers. Cobalt ferrite nanoparticles are considered one of the most promising metal-oxide nanomaterials because of their favorable magnetic properties, such as high saturation magnetization and magnetic anisotropy. The substitution of Co²⁺ in cobalt ferrite with other transition metals allows for additional tailoring of these properties. The modified magnetic behavior of the substituted CoFe₂O₄ nanoparticles directly influenced the magnetic properties of magnetic elastomers and, consequently, the magnetoelectric response of composite structures. In this case, the resonant frequency of the magnetoelectric effect remained largely independent of the type of magnetic nanoparticles in the magnetic elastomer layer but its magnitude increased upon Zn substitution up to ~107 mV·cm⁻¹·Oe⁻¹. These findings highlight the potential of chemically engineered magnetic properties of CoFe₂O₄ nanoparticles for manufacturing magnetoelectric composites to expand their applications in energy harvesting and sensors. Full article

The continuous discovery of novel effective antibacterial agents using nano-based materials is of high significance. In this study, we utilized Polymerylated divalent-metal-doped ferrite nanoparticles (PMFe₂O₄ NPs) and studied their antibacterial inhibition effects. Different panels of PVP- and PEG-coated metal-doped MFe₂O₄ (M ≅ Co, Ni, and Zn) were prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology and thoroughly analyzed using TEM, XRD, FTIR, and VSM. The as-synthesized doped ferrites displayed stable quasi-spherical particles (7–15 nm in size), well-ordered crystalline cubic spinel phases, and high-saturation magnetizations reaching up to 68 emu/g. The antibacterial efficacy of the doped ferrites was then assessed against a Gram-negative E. coli bacterial strain. The results demonstrated that both metal doping and polymer functionalization influence the antimicrobial efficacies and performance of the ferrite NPs. The presence of the PVP polymer along with the divalent metal ions, particularly Co and Ni, resulted in the highest antibacterial inhibition and effective inactivation of the bacterial cells. The antibacterial performance was as follows: PVP-CoFe₂O₄ > PVP-NiFe₂O₄ > PVP-ZnFe₂O₄. Lastly, cell viability assays conducted on human breast fibroblast (HBF) cells confirmed the good safety profiles of the doped ferrites. These interesting results demonstrate the distinctive inhibitory features of the biocompatible metal-doped ferrites in enhancing bacterial killing and highlights their promising potential as effective antimicrobial agents, with possible applications in areas such as water disinfection, biomedical devices, and antimicrobial coatings. Full article

The widespread use of gadolinium (Gd) in medical and industrial applications, especially as a contrast agent in magnetic resonance imaging (MRI), has led to its increasing presence in surface waters, disrupting natural geochemical cycles and posing risks to aquatic ecosystems. Addressing this challenge, recent studies have explored the potential of magnetic materials, such as spinel ferrite nanoparticles, in the removal of Gd from contaminated water sources. The present study specifically focused on the use of MnFe₂O₄ nanoparticles to remove Gd from contaminated solutions, employing response surface methodology (RSM) to optimize sorption conditions. Key variables evaluated included salinity (0–30 g/L), initial Gd concentration (1–5 μmol/L), and sorbent dose (20–180 mg/L), at a fixed pH of 6. The results revealed that salinity had a minimal impact on Gd sorption, likely due to the high sorbent mass used. Optimal conditions were identified as a sorbent dose of 165 mg/L, an initial Gd concentration of 1.3 μmol/L, and a salinity level of 13.4 g/L, at pH 6. The process was efficient and rapid, achieving over 90% Gd removal within 1 h in both freshwater and saline conditions, and over 75% removal in mineral water within 3 h. The high efficiency and celerity of this method suggest that MnFe₂O₄ nanoparticles are a promising solution for treating Gd-contaminated hospital effluents. Future research should focus on validating these results in real-world effluent matrices and addressing the environmental and economic aspects of large-scale implementation, thereby contributing to sustainable water remediation strategies. Full article

Nanotechnology has been a source of innovation in various fields in recent years, and its application in agriculture has attracted much attention, particularly for its potential to enhance crop growth and optimize nutritional quality. This study systematically investigated the effects of nickel ferrite nanoparticles (NiFe₂O₄ NPs) on peanut (Arachis hypogaea L.) growth, nutrient dynamics, and biochemical responses, highlighting their potential as sustainable alternatives to conventional fertilizers. The results showed that an optimum concentration of 50 mg/kg soil significantly improved photosynthetic efficiency, biomass accumulation, seed yield, and nutritional quality, with 1000 seed weight and total yield increasing by 12.3% and 15.6%, respectively. In addition, we hypothesized that NiFe₂O₄ NPs would activate the antioxidant system and increase plant resistance. According to the risk assessment, the target hazard quotient (THQ = 0.081) is well below the safety threshold of 1. These findings provide strong evidence for the application of NiFe₂O₄ NPs as next-generation nano-fertilizers, offering a dual advantage of improved agronomic performance and biosafety. However, further research is needed to optimize their application strategies and assess potential long-term environmental impacts. Full article

High-concentration polyvinyl alcohol (PVA) wastewater from 3D printing applications presents significant treatment challenges due to PVA’s water solubility, chemical stability, and resistance to biodegradation. In this study, we investigated the enhanced removal of high-concentration PVA (3–7 g/L) using a modified ferrite process with H₂O₂ pre-oxidation, while simultaneously exploring the formation and properties of magnetic precipitates. The effects of PVA concentration, reaction conditions, and thermal treatment (100 °C and 650 °C) on the magnetic precipitates were studied through XRD, TEM, FTIR, and magnetic measurements. Results showed that H₂O₂ pre-oxidation effectively maintained the system pH and improved PVA removal efficiency, achieving a COD reduction of 83% after two-stage treatment for 7 g/L PVA solution. XRD and TEM analyses revealed that precipitates formed at 100 °C consisted of dispersed Fe₃O₄ nanoparticles within PVA fibrous networks, while calcination at 650 °C led to the formation of rod-like structures and agglomerated particles. The magnetic properties varied significantly with treatment conditions, exhibiting the highest saturation magnetization of 10.30 emu/g for sample calcinated at 100 °C. This study demonstrates the potential of the modified ferrite process for treating high-concentration PVA wastewater while producing recoverable magnetic nanoparticles, providing a dual-function approach to address environmental challenges posed by the 3D printing industry. Full article