Search Results (444)

Multiferroic composite semiconductor fibers enable non-contact magnetic control but may also operate under spatially nonuniform thermal conditions. This study develops a one-dimensional analytical model for a symmetric CoFe₂O₄/ZnO/CoFe₂O₄ fiber subjected to local magnetic and temperature fields with independently prescribed widths. The model combines piezomagnetic, piezoelectric, pyroelectric, thermoelastic, and semiconductor effects and provides closed-form solutions for the electric potential, electric field, polarization, and electron concentration perturbation. Local magnetic and thermal inputs generate localized potential barriers and wells through distinct pathways. Where the excitation regions overlap, their contributions may reinforce, compete with, or partially cancel each other. The initial electron concentration affects the carrier-screening strength and spatial localization of the electrical response, whereas the layer-thickness ratio influences the competition between piezomagnetic actuation and piezoelectric conversion. An independent finite-element calculation closely reproduces the analytical potential distribution for the baseline case. This study clarifies the interaction between the magnetic and thermal contributions to open-circuit carrier redistribution and provides a field-distribution baseline for future biased, contact-resolved transport analyses of multiferroic micro- and nanostructures. Full article

Osteoarthritis is an irreversible degenerative joint disease driven by sustained NF-κB-mediated inflammatory responses, and conventional intra-articular hyaluronic acid or small-molecule NF-κB inhibitors cannot achieve targeted on-demand treatment due to poor solubility, rapid clearance and lack of lesion microenvironment responsiveness. OA with inherent anti-chondrolytic activity can self-assemble into nanocarriers in water, yet it lacks stimuli-responsive capacity. Herein, we rationally designed and synthesized an OA-Der by covalently conjugating o-phenylenediamine fragments to the OA backbone. ¹H NMR and HRESI-MS spectra fully verified the accurate chemical structures of intermediate and final OA-Der. Blank OA-Der micelles exhibited uniform spherical core–shell nanostructures (50–150 nm) under TEM and AFM, while pathological high NO triggered complete disassembly of micellar assemblies. We further co-assembled OA-Der with NF-κB inhibitor BAY 11-7082 to construct NO-responsive BAY@OA-Der supramolecular micelles. In vitro experiments using human C28/I2 chondrocytes with LPS-induced inflammatory injury demonstrated that BAY@OA-Der significantly improved cell viability and reduced apoptotic chondrocyte proportion. At mRNA and protein levels, the supramolecular micelle formulation remarkably suppressed NF-κB p65 phosphorylation, downregulated cartilage-degrading ADAMTS5, and upregulated ACAN compared with free BAY or blank OA-Der. Collectively, this natural bioactive self-assembled NO-responsive delivery platform achieves synergistic anti-inflammatory and matrix-protective effects by precisely releasing drugs at NO-overexpressed osteoarthritis inflammatory sites and offers an in vitro design strategy for osteoarthritis responsive delivery systems. Full article

Yeast-assisted mixed-culture fermentations have gained attention for their ability to enhance fermentation efficiency and modulate metabolite production. There is little knowledge on the impact of magnetic nanoparticle-assisted immobilization on yeast–yeast interactions during alcoholic fermentation. The co-culture platforms of Saccharomyces cerevisiae and Kluyveromyces marxianus, immobilized on chitosan-coated manganese ferrite nanoparticles, were applied in the fermentation of sugarcane molasses and sugarcane juice in the present study. The chitosan-coated MnFe₂O₄ nanoparticles were prepared using a one-step coprecipitation reaction followed by hydrothermal treatment and were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy. An immobilized co-culture system has been shown to provide faster sugar consumption and higher ethanol production than non-immobilized-cell fermentations. Operational stability of the immobilized biomass and higher ethanol production by reuse were confirmed by repeated fermentation cycles. Bioproduction of volatile metabolites varies among monoculture, co-culture, non-immobilized-cell, and immobilized systems, with yeast interactions and magnetic immobilization also affecting secondary metabolite production during fermentation. The findings confirm that magnetic nanoparticle-assisted co-culture fermentation would be an attractive nanobiotechnological tool for enhancing alcoholic fermentation and shed new light on yeast interactions with the nanostructured system when combined with the immobilized solution. Full article

Nanostructured copper oxide (CuO) holds significant promise for optoelectronic, photocatalytic, and biomedical applications, yet its performance is critically dictated by its morphology, crystallite size, and surface chemistry. In this work, pure monoclinic CuO nanoparticles were successfully synthesized via a facile, kinetically controlled aqueous co-precipitation route using three distinct precursor salts: copper acetate (CO-Ac), copper sulfate (CO-S), and copper chloride (CO-Cl). To achieve precise architectural control, the synthesis was conducted near the thermodynamic solubility limit of the precursors combined with an abrupt NaOH injection, effectively decoupling the nucleation stage from crystal growth. Rietveld refinement of X-ray diffraction (XRD) data confirmed the structural integrity of the monoclinic lattice across all samples, χ² = 1.04 − 2.02, crystallinity 53–55%, while demonstrating that the precursor anion strongly governs the volume-averaged crystallite size, which expanded from 16 nm (CO-Ac) to 30 nm (CO-S) and 52 nm (CO-Cl). Morphological analyses revealed that acetate acts as a non-specific capping ligand, promoting isotropic, quasi-spherical nanoparticles that aggregate into high-surface-area (69.04 m²/g) “bead-chain” assemblies. Conversely, sulfate and chloride ions act as shape-directing agents via facet-selective adsorption on nucleation seeds, yielding two-dimensional plates and anisotropic acicular/needle-like architectures, respectively. X-ray photoelectron spectroscopy (XPS) and modified Auger parameter (α ~1851 eV) analyses confirmed the absolute dominance of Cu²⁺ states, with a minor fraction (~2.5 mol %) of lower-coordinated surface edge states. XPS further unveiled that the strongly alkaline environment (pH ~14) drives precursor-dependent surface chemistry: CO-Ac nanoparticles retain a clean, hydroxylated layer with minor acetate residues, whereas CO-S and CO-Cl samples develop a passive copper hydroxycarbonate (Cu₂(OH)₂CO₃) surface barrier that blocks active sites and reduces porosity. Optical properties analyzed via UV-vis diffuse reflectance revealed a pronounced, size-dependent blueshift relative to bulk CuO, with fundamental indirectly allowed bandgaps of 2.6 eV, 2.36 eV and 1.93 eV for CO-Ac, CO-S and CO-Cl samples, while the direct bandgaps shifted from 3.0 eV, 3.2 eV, and 3.57 eV for the mentioned samples. This behavior is attributed to quantum confinement governed by fine individual nanocrystals. These findings establish that precursor engineering offers a robust pathway to tailor the morphological, optical, and interfacial properties of CuO nanostructures for targeted functional devices. Full article

Molten carbonate salt nanofluids have emerged as a promising approach to improve the power generation efficiency of next-generation concentrated solar power (CSP) systems due to their enhanced thermophysical properties at high temperatures. However, corrosion upon salt nanofluids remains a key challenge for the use of cost-effective steels as construction materials in CSP applications. In this work, the corrosion behavior of AISI 301LN stainless steel exposed to molten carbonate salt nanofluids containing 1.0 wt.% SiO₂ nanoparticles with <20 nm and <50 nm has been studied. Corrosion tests were conducted in a static Li₂CO₃-Na₂CO₃-K₂CO₃ molten salt mixture at 600 °C for 1000 h. The oxide scales formed after exposure to the three nanofluids and the base salt were compared. The results revealed that the corrosion rate of AISI 301LN steel on molten salt was reduced by the addition of SiO₂ nanoparticles. The incorporation of SiO₂ nanoparticles into the oxide scale leads to the formation of dense reticulated nanostructures composed of Si-containing oxides, respectively. This increases the hardness of the oxide scale and enhances its protective performance in molten salt, particularly when using SiO₂ nanoparticles with the smallest size (<20 nm). Full article

During aviation operations, low temperatures can cause fuel freezing and icing on 6061 aluminum fuel lines, threatening flight safety. To mitigate this, a surface treatment combining FeCl₃ etching and an ORMOSIL sol–gel coating was proposed to construct a superhydrophobic functional layer. FeCl₃ etching generated a hierarchical micro/nanostructure on the aluminum surface, while the ORMOSIL layer, formed by the co-hydrolysis and condensation of PFOTES and HDTMS, built Si-O-Si networks and introduced C-F groups to reduce surface energy and enhance stability. The modified surface showed a high water contact angle of 161.44°, confirming excellent superhydrophobicity. AFM analysis revealed a significant increase in surface roughness (Sa = 0.844 μm), confirming the formation of a hierarchical micro/nanostructure. Electrochemical measurements showed a positive shift in corrosion potential from −0.723 V to −0.652 V, demonstrating enhanced corrosion resistance. More importantly, after 120 h of immersion in aviation fuel, the coating maintained a high contact angle of 156.73° and preserved its Si-O-Si network and fluorinated functional groups, confirming outstanding fuel resistance and long-term stability. These results demonstrate that the proposed ORMOSIL coating is a promising protective strategy for aviation fuel systems operating under low-temperature and corrosive conditions. Full article

This study investigates the synthesis–structure relationships governing sol–gel-derived nanostructured MgFe₂O₄ ferrite powders for high-temperature thermochemical energy conversion applications. The effects of key processing parameters, including propylene oxide (PO) concentration, gel aging time, calcination temperature, and calcination duration, were systematically examined to tune the phase composition, specific surface area (SSA), pore volume, crystallite size, and nanoparticle morphology of MgFe₂O₄. Increasing the PO concentration from 5 to 20 mL shortened the gelation time from 585 to 323 s and increased the SSA from 5.30 to 17.88 m²/g, while the pore volume increased from 0.0074 to 0.0210 cm³/g. In contrast, gel aging time between 24 and 120 h produced negligible changes in SSA, pore volume, and crystallite size, indicating that extended aging is not required for microstructural control. Calcination temperature strongly influenced the nanostructure: increasing the temperature from 600 to 1000 °C decreased SSA and pore volume while increasing crystallite size from 21.33 to 48.76 nm. Longer calcination times produced a similar but less pronounced effect, decreasing SSA from 18.83 to 14.89 m²/g and increasing crystallite size from 17.55 to 30.12 nm. Overall, phase-pure MgFe₂O₄ with favorable textural properties was obtained using 20 mL of PO, 24 h of aging, and calcination in the 700–800 °C range. Under the identified synthesis conditions, namely 20 mL of PO, 24 h of aging, and calcination in the range of 700–800 °C for 2 h, phase-pure MgFe₂O₄ nanoparticles with particle sizes of approximately 10–50 nm were obtained. These results establish a processing–microstructure framework for engineering MgFe₂O₄ nanomaterials with tunable textural properties for solar thermochemical redox cycles and related high-temperature energy applications. Full article

Nanostructured Co₃O₄ was synthesized via a sol–gel approach employing the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIm]TfO) and subsequently evaluated as a high-performance anode material for lithium-ion batteries. Ionic liquids, distinguished by their low volatility, high thermal stability, and tunable chemical properties, represent a greener alternative to conventional organic solvents for the synthesis of functional nanomaterials. The electrochemical performance of the as-prepared material was systematically assessed through galvanostatic charge–discharge cycling, cyclic voltammetry, and rate capability tests. The Co₃O₄ electrode exhibited a high reversible capacity of approximately 1100 mAh g⁻¹ after 50 cycles at a current density of 200 mA g⁻¹, along with excellent coulombic efficiency approaching ~100% after the initial cycles. Furthermore, the material demonstrated strong rate capability, delivering about 600 mAh g⁻¹ at 1 C, and recovering its capacity upon returning to lower current densities. The improved electrochemical performance is primarily attributed to the nanoscale architecture induced by the ionic liquid-assisted synthesis, which facilitates rapid lithium-ion transport and effectively buffers volume variations during repeated cycling. Notably, the ionic liquid serves a dual function as both a green reaction medium and a structure-directing agent, enabling precise control over the material’s morphology and properties. This study demonstrates a versatile strategy for the rational design of potential transition-metal oxide anodes, paving the way for high-performance electrode materials. The findings contribute to the development of next-generation lithium-ion batteries tailored for clean and sustainable energy storage applications. Full article

Nickel ferrite (NiFe₂O₄) is one of the most studied inverse-spinel ferrites because it combines moderate saturation magnetization, comparatively high electrical resistivity, chemical stability, and broad synthesis flexibility. Yet the literature shows that the measured structure and magnetism of NiFe₂O₄ are not intrinsic constants; they evolve strongly with dimensionality, size, thickness, strain state, cation distribution, surface spin disorder, and synthesis pathway. This review develops a unified theoretical and literature-based interpretation of how dimensionality reshapes the structural and magnetic behavior of NiFe₂O₄ across bulk ceramics, nanoparticles, one-dimensional nanostructures, polycrystalline thin films, and ultrathin epitaxial films. The review is anchored in the two uploaded nickel ferrite attachments and expanded using internet-sourced journal literature on spinel inversion, surface effects, mechanochemical synthesis, sputtered and pulsed laser deposited thin films, and epitaxial ultrathin-film anomalies. The central novelty of this article is the formulation of a dimensionality-dependent framework in which the observed magnetic response is governed by a competition among three coupled factors: (i) the cation-distribution function, which controls the A–B superexchange balance and therefore the net ferrimagnetic moment; (ii) the microstructural coherence function, which measures how crystallinity, strain, defects, and anti-phase boundaries preserve or degrade exchange continuity; and (iii) the surface/interface spin-order parameter, which quantifies the loss or reconfiguration of magnetic order at free surfaces and buried interfaces. Within this framework, bulk NiFe₂O₄ behaves as a near-equilibrium inverse spinel with relatively stable magnetization, whereas nanoscale NiFe₂O₄ experiences strong spin canting and finite-size suppression due to the growing fraction of disordered surface spins. Thin films introduce a distinct regime in which strain, texture, anti-phase boundaries, substrate mismatch, and growth kinetics determine both anisotropy and magnetization. In ultrathin epitaxial films, off-equilibrium cation redistribution and interface-controlled electronic reconstruction may even generate magnetization values far above bulk expectations. The review also compares major synthesis routes—solid-state reaction, sol–gel, co-precipitation, hydrothermal growth, reactive milling, combustion, pulsed laser deposition, and radio-frequency sputtering—and explains why each route biases the final dimensionality-dependent properties differently. A set of word-style equations is provided to formalize spinel inversion, finite-size suppression, anisotropy scaling, coercivity trends, and superparamagnetic crossover. Beyond summarizing the field, the review proposes a regime map linking dimensionality to characteristic structural defects and magnetic signatures, and it identifies unresolved questions concerning the true origin of enhanced magnetization in ultrathin NiFe₂O₄, the interplay between anti-phase boundaries and strain, and the distinction between intrinsic inversion changes and extrinsic substrate artifacts. The resulting article offers a submission-ready, originality-focused review that positions dimensionality as the master variable governing structure–magnetism correlations in nickel ferrite. Full article

This study investigates the formation mechanism of non-doped cubic lithium lanthanum zirconium oxide (c-LLZO) nanofibers using in situ synchrotron X-ray scattering techniques. Electrospun polymer precursor nanofibers were annealed at temperatures up to 800 °C, enabling real-time tracking of phase transitions via simultaneous small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and evolved CO₂ gas analysis. The results reveal a three-step transformation pathway: polymer decomposition, formation of La₂Zr₂O₇ (LZO), and direct conversion of LZO to c-LLZO without intermediate tetragonal phases detected within the sensitivity of our in situ WAXS measurement. Cryo-electron energy loss spectroscopy (EELS) further elucidates the role of lithium diffusion, showing Li enrichment at fiber surfaces and Li deficiency in the interior, which stabilizes the cubic phase. This Li segregation effect in nanostructured LLZO materials extends beyond the previously reported size effect. This work advances the understanding of c-LLZO formation mechanisms and provides practical insights for optimizing synthesis routes to achieve phase-pure c-LLZO for solid-state battery applications. Full article

Wear remains a dominant cause of performance loss and premature failure in mechanical components, motivating the development of environmentally benign surface-engineering solutions. Among thermal spray systems, high-velocity oxy-fuel (HVOF)-sprayed WC-Co coatings are widely applied under severe wear conditions. The development of nanophase coatings offers the potential for enhanced mechanical performance. However, retaining the nanostructure and limiting decarburization during deposition remain key challenges. In this study, nanophase WC-12Co feedstocks with two particle size ranges, together with Al-modified nanophase powders, were used to deposit coatings under optimized HVOF spraying conditions (spray distance 200 mm, reduced O₂/fuel ratio, and high particle velocity) and were benchmarked against a conventional WC-12Co (12 wt.% Co) coating. The coatings were characterized in terms of microstructure and phase constitution (OM, SEM/EDS, XRD) as well as thickness, porosity (0.5–3.6%), adhesion strength (up to 65 MPa), and microhardness (~1040–1210 HV). Tribological behavior was assessed by ASTM G99 pin-on-disk testing and counterbody wear was quantified via geometric volume loss estimations. The use of larger nanophase particles enabled effective nanostructure retention with limited decarburization, whereas reducing particle size intensified decarburization, promoting increased W₂C formation, and markedly reduced coating cohesion, despite lower porosity and higher hardness. Aluminum additions enhanced coating microhardness and suppressed Co₃W₃C formation, indicating improved phase stability with minimal additional decarburization. Although coating wear remained negligible for all systems, Al-containing coatings exhibited increased friction (up to 35%) and significantly higher counterbody wear (up to sevenfold) compared to the Al-free nanophase coating, which was found to correlate with coating microhardness. Overall, the results demonstrate that optimizing nanophase WC-Co coatings requires balancing competing mechanisms between microstructural stability, cohesive integrity, and tribological response, highlighting the critical role of feedstock design in tailoring coating performance. Full article

In this study, cobalt oxide (Co₃O₄) ceramics were synthesized using the sol–gel method and calcined at 300 °C and 600 °C to investigate the influence of thermal treatment on their structural, thermal and optical properties. X-ray diffraction (XRD) analysis confirmed the successful formation of a pure cubic spinel Co₃O₄ phase with nanocrystalline features, belonging to the Fd3m space group. As the calcined temperature increased, the samples exhibited enhanced crystallinity, with the average crystallite size ranging from 15 to 26 nm, sharper and more intense diffraction peaks, indicating grain growth and improved structural ordering. Thermogravimetric analysis (TGA) indicated the elimination of surfaceadsorbed species and residual organics during the initial stages, succeeded by the stabilization of a pure cubic spinel Co₃O₄ phase, which exhibits remarkable thermal stability without any additional phase transitions. UV–Vis diffuse reflectance spectroscopy (DRS) analysis showed that the Co₃O₄ nanostructures displayed significant absorption in the visible region, consistent with their intrinsic narrow band gap characteristics. Unlike earlier sol–gel synthesized Co₃O₄ ceramics, the present work highlights enhanced crystallinity and structural development with increasing calcination temperature. Full article

In this work, we report the fabrication of SnO₂-based composite nanostructures in view of their application as a sensor element toward N₂O gas exposure. The samples were produced by laser ablation of a composite SnO₂-TiO₂ target performed in air at atmospheric pressure (in open air). We examined how the structure, morphology, composition, and physical properties of the samples change with the TiO₂ content being introduced into the SnO₂ target. The laser ablation of SnO₂-based targets in open air produced samples with a structure in which SnO₂ and SnO crystal phases co-existed, as the crystal phases were distinguished in separate nanoparticles. The nanoparticles formed a complex porous structure with oxygen-related defects. We investigated the gas-sensing properties of composite SnO₂-based sensor elements working under UV irradiation. The highest response to N₂O exposure and the fastest response/recovery times were demonstrated by the sensor element produced by the laser ablation of a composite target prepared by 10 wt% TiO₂ in SnO₂. Additionally, we found that a small amount (below 0.1 wt%) of noble metal (Pt) added to the sensor element substantially improved the gas sensor performance without inducing significant structural and/or morphological changes. Further, we explored how simultaneous irradiation of the sensor surface with UV and visible light changes the sensor properties. The best sensor performance toward N₂O exposure was achieved by irradiating the Pt-doped SnO₂-TiO₂ sensor surface simultaneously with UV and red lights. Full article

CoFe₂O₄ nanoparticles were prepared using a hydrothermal method. All the studied samples were single-phase and were crystallized in a cubic Fd-3m structure. XRD and TEM analyses revealed that the particles had average sizes between 5 and 22 nm. It has been shown that, by using the PVP of different molecular masses, trends of growth and crystallization can be established, obtaining elongated 40 k, cubical 58 k, and rhomboidal 360 kg/mol nanoparticles. While using Ethylene glycol as solvent, the formation of separated “raspberry”-like nanostructures was revealed. The saturation magnetizations are somewhat smaller compared with crystalline CoFe₂O₄ saturation magnetization, but are high enough to have possible biomedical applications. FC and ZFC measurements show that the blocking temperature was around 100 K for the CF5 sample and around 20 K for the FC6 sample. The calculated anisotropy constants were between 7 and 10 kJ/m³, being close to previously reported values. The calculated blocking temperatures are in good agreement with experimental ones. The M_r/Ms ratio at room temperature was lower than 0.5, confirming the predominance of magnetostatic interactions. This paper serves as a good starting point for researchers seeking to synthesize a CoFe₂O₄ system with a desired size and growth tendency at the nanometer scale. Full article

This study investigates the properties of ZnO nanorod-based sensors and ZnO nanorods modified with tin dioxide (ZnO/SnO₂) and gold (ZnO/Au) nanoclusters and their response to low concentrations of carbon monoxide (CO). It was demonstrated that the ZnO/SnO₂(3) nanorod-based sensor exhibited the highest sensitivity (S = 1.64) to 10 ppm CO, while the ZnO/Au(3) sensor displayed the shortest response (69–207 s) and recovery (203–233 s) times. This behavior can be explained by ZnO/Au and ZnO/SnO₂ nanostructures having low activation energies (0.23–0.25 eV) and high potential barrier values (0.37–0.43 eV). Sensors based on ZnO/Au and ZnO/SnO₂ nanorods demonstrate sensitivity to 10 ppm CO at 250 °C and at 200 °C. In contrast, ZnO nanorod-based sensors are sensitive to 2 ppm CO at 250 °C. Full article