Search Results (1,050)

Structural colors, generated by the physical interaction of light with micro- and nanostructured architectures, have emerged as an important platform in nanophotonics owing to their high color saturation, exceptional photostability, and long-term color durability. This review provides a comprehensive overview of recent advances in structural colors and establishes a unified classification framework based on their macroscopic angular optical responses. The intrinsic angular characteristics of four fundamental color-generation mechanisms are first distinguished, providing the physical basis for classifying structural colors into iridescent and non-iridescent systems. Representative iridescent architectures, including thin films, one-dimensional (1D) to three-dimensional (3D) photonic crystals, and diffraction gratings, are systematically reviewed, together with non-iridescent strategies based on independent plasmonic and dielectric resonators, quasi-amorphous structures, and engineered metasurfaces. Strategies for enhancing structural color visibility and saturation through absorption management are further discussed, particularly for suppressing undesired broadband and multiple-scattering backgrounds. Additionally, this review systematically summarizes quantitative methodologies for evaluating structural colors, including spectral metrics, CIE 1931 and CIE1976 color spaces, CIEDE2000 color difference, quantitative angular-response metrics, spatial resolution and pixel limits, and structural-order characterization using orientation parameters and two-dimensional fast Fourier transform (2D FFT) analysis. Particular attention is given to the quantitative assessment of angular stability through wavelength shifts and perceptual color differences, while recognizing that a universally accepted numerical boundary between iridescent and non-iridescent coloration has not yet been established. Representative functional applications are also reviewed, including self-cleaning coatings, passive daytime radiative cooling, label-free chemical and gas sensing, reflectometric interference spectroscopy (RIfS), surface-enhanced Raman scattering (SERS), and anti-counterfeiting. By integrating color-generation mechanisms, angular optical responses, quantitative evaluation methods, and functional applications, this review provides a unified framework for objectively comparing structural color platforms and highlights key trade-offs among color quality, angular stability, structural precision, durability, scalability, and multifunctionality, thereby providing design guidance for next-generation optical materials and devices. Full article

Background/Objectives: The stability and biological safety of newly developed formulations must be established to support their therapeutic efficacy and clinical translation in pulmonary drug delivery. Therefore, this follow-up study comprehensively evaluated the short- and long-term stability and the in vitro cytotoxicity of optimized, co-spray-dried theophylline (THN) dry powders for inhalation against A549 lung epithelial cells. Methods: Two established formulations were selected: THN-RAF (raffinose–leucine–glycine based) and THN-TRE (trehalose–leucine based). Stability was assessed under accelerated conditions (40 °C/75% RH, 3 months) and long-term desiccator storage (25 °C, 1 year) using laser diffraction, SEM, XRPD, FTIR, DSC, TGA, and Andersen Cascade Impaction. As THN-TRE had been previously confirmed to be cytocompatible, only THN-RAF and its components were evaluated against A549 human alveolar epithelial cells using the MTT assay. Results: Under accelerated conditions, both formulations exhibited pronounced recrystallization (Xc up to 89.9%), agglomeration (D [0.9] up to 217.08 µm for THN-TRE), and deterioration in aerodynamic performance (FPF as low as 11.55%, MMAD up to 6.68 µm). By contrast, long-term desiccator storage induced substantial recrystallization (Xc up to 80.7%) while preserving thermal, chemical, and aerodynamic performance (FPF ≈ 40%; MMAD 4.99–5.21 µm). THN-RAF was more resistant to stress-induced agglomeration than THN-TRE. Cytotoxicity assessment confirmed cytocompatibility of THN-RAF, with cell viability exceeding 70.99% at all tested concentrations (up to 500 µg/mL). Conclusions: These findings reveal a marked discrepancy between the outcomes of ICH accelerated testing and long-term desiccator storage. They underscore the importance of considering moisture-protective packaging configurations when designing stability protocols for amorphous inhalable formulations. Full article

Background/Objectives: This study evaluated the influence of sintering conditions and acidic environments on the wear of 5 mol% yttria-stabilized zirconia (5Y-ZP). Methods: Sixty zirconia specimens were divided into two sintering groups (conventional and speed) and three immersion media (n = 10): distilled water, Coca-Cola, and vinegar. Wear testing was performed using a chewing simulator under a 49 N load for 120,000 cycles, simulating 6 months of clinical function. Volume loss, mean wear depth, and surface roughness were measured using a 3D profilometer. Surface and compositional analyses were performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Results: Significant differences in wear were observed (p < 0.05). The greatest wear occurred in distilled water (58.927 ± 13.199 µm; 0.3518 ± 0.1062 mm³ for speed-sintered and 53.408 ± 6.784 µm; 0.3211 ± 0.0546 mm³ for conventional). Vinegar produced moderate wear (15.478 ± 2.584 µm; 0.0482 ± 0.0142 mm³ and 11.575 ± 3.334 µm; 0.0360 ± 0.0116 mm³), whereas Coca-Cola produced the least (2.899 ± 1.377 µm; 0.0049 ± 0.0027 mm³ and 1.870 ± 0.688 µm; 0.0027 ± 0.0012 mm³). Sintering condition affected only wear depth. SEM showed localized surface alterations in acidic media, EDS revealed reduced yttria content, and XRD revealed no detectable monoclinic phase, with no interaction between variables. Conclusions: Acidic environments had a greater influence on the wear of 5Y-ZP zirconia than sintering conditions. Speed sintering influenced wear far less than the immersion medium, supporting its use in patients exposed to acidic conditions. Full article

We used powder X-ray diffraction (XRD) and ac impedance spectroscopy to investigate the polymorphic phase transitions undergone by the MH₂PO₄ (M = Cs, K, Rb) proton conductor series upon heating. High-pressure methods used in conjunction with energy dispersive XRD enhanced by synchrotron radiation allowed us to isolate a pure cubic (superprotonic) RbH₂PO₄ (RDP) polymorph (at P = 1.2 GPa and T = 320 °C) and collect data of enough quality to Rietveld refine its crystal structure. Our data and analysis reveal that cubic RDP (Pm-3m, a = 4.76 ± 0.01 Å) is described by a unit cell where Rb and P atoms are in (0, 0, 0) and (0.5, 0.5, 0.5) positions, respectively, whereas O atoms are in (0.5, 0.234(5) 0.342(6)) positions having a multiplicity of 24 and an occupancy of 0.166. This results in dynamically disordered PO₄ tetrahedra that enables the superprotonic conduction in RDP, a mechanism like the one in the high-temperature cubic phase of the Cs-based compound CsH₂PO₄ (CDP). This is a notable behavior, as RDP and CDP are structurally different at room temperature—RDP is tetragonal (I-42d) and CDP is monoclinic (P2₁/m)—but following polymorphic modifications upon heating they both end up in superprotonic cubic phases that are isostructural to one another. On the other hand, we found that although the K-based phosphate KH₂PO₄ (KDP) has the same crystal structures as RDP at room and at intermediate temperatures, further heating does not lead to a cubic KDP phase. Overall, our results are significant from both the fundamental and applied perspective as superprotonic phosphates are promising materials for fuel cell electrolyte applications. Full article

In recent years, multifunctional composite nanoparticles have garnered substantial attention across multiple fields, from medicine to environmental science and the food industry, owing to their superior physicochemical properties. The synching of Ni nanoparticles by chemical reduction with nickel chloride as the source, and Fe₃O₄ nanoparticles by the co-precipitation method, with Fe²⁺ and Fe³⁺ as salts, is the focus of this study. Silane was used for the surface modification of Fe₃O₄ nanoparticles, while sulfuric acid was used to modify the SMCNT. A composite in PVDF based on the blend of Ni and modified Fe₃O₄/single-walled carbon tube (SWCNT) was used as an additive. Moreover, thermoplastic polyurethane (TPU) was hot-pressed over the film to improve flexibility. To examine and characterize the nanoparticles and composite films, we used X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive spectroscopy (EDS). The results verified that the films and nanoparticles were well formed. For a deeper characterization, UV-visible spectroscopy and EMI shielding experiments were conducted for the composite films. The composite films exhibited excellent UV-blocking performance (99.9%) and a total shielding effectiveness (SET) of 13.78 dB in the Ku-band (12–18 GHz) for a thickness of 1 mm. The reflection and absorption mechanisms yield shielding performance through the synergy between conducting (Ni, SWCNT) and magnetic (Fe₃O₄) components. These results reveal that the TPU-coated composite film is a promising candidate for multifunctional UV and electromagnetic shielding. Full article

A technological approach to the formation of a 3D nanocomposition material based on hierarchical porous nickel oxide nanoparticles incorporated into porous silicon with a dendritic porous structure is proposed. Porous silicon was used as a 3D porous template, in the presence of which porous hierarchical nickel oxide nanoparticles were synthesized using a “green” synthesis method followed by annealing in an oxygen-containing atmosphere. The resulting materials were characterized using scanning electron microscopy, transmission electron microscopy, X-ray spectral microanalysis, X-ray diffraction, and the BET method. The potential of a developed composition based on porous hierarchical nickel and silicon oxide nanoparticles to enhance the sensitivity of adsorption gas sensors was assessed using impedance spectroscopy in the presence of a probe gas (isopropanol). Gas sensitivity measurements were conducted at room and elevated temperatures in the frequency range from 100 Hz to 500 kHz. Differences in the dependences of the real part of impedance on the imaginary part were revealed for the porNiO-porSi composition in Nyquist coordinates. The results are discussed in terms of percolation theory and fractal organization. Full article

Background/Objectives: Baicalin (BA), a natural flavonoid with anti-inflammatory activity, shows promise for treating acute pharyngitis (AP) but its clinical application is hindered by poor water solubility and low oral bioavailability. Based on the clinically validated traditional Chinese medicine formula Pudilan Oral Liquid, we identified that BA and chlorogenic acid (CGA) can self-assemble into nanocomplexes (BA-CGA@NPs). This study aims to construct such a nanocomplex to enhance BA absorption and anti-AP efficacy with favorable biocompatibility. Methods: BA-CGA@NPs were prepared via supramolecular self-assembly and characterized by dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and molecular dynamics simulation (MDS). In vivo pharmacokinetics evaluated BA absorption. Biocompatibility and therapeutic efficacy were assessed using lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages and an AP rat model. Results: BA-CGA@NPs were successfully formed with enhanced biocompatibility. In vitro, they reduced nitric oxide (NO), reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β) in macrophages. In AP rats, oral BA-CGA@NPs significantly increased systemic BA exposure, ameliorated pharyngeal histopathology, and lowered IL-1β, TNF-α, and interleukin-6 (IL-6) in serum and pharyngeal tissue, outperforming free BA or CGA alone. Mechanistic studies suggested that the anti-inflammatory effect was associated with modulation of the Toll-like receptor 4 (TLR4)/MyD88/Nuclear factor-κB (NF-κB) signaling pathway. Conclusions: Self-assembled BA-CGA@NPs enhance BA absorption and biocompatibility, alleviating AP inflammation through mechanisms associated with modulation of the TLR4/MyD88/NF-κB pathway, offering a promising nano-traditional Chinese medicine strategy for poorly soluble active ingredients. Full article

The development of reusable nanomaterials for the extraction of trace-metals from complex matrices remains challenging because strong metal-chelating functionalities often hinder desorption and regeneration, whereas weaker binding sites compromise selectivity and enrichment efficiency. This limitation has been addressed by designing a ligand-engineered fibrous mesoporous silica nanomaterial (Van-KCC-1) via the integration of the unique structural features of KCC-1 with an o-vanillin-derived Schiff-base chelator. The material was synthesized throughout the chemical grafting of 3-aminopropyltriethoxysilane (APTES) onto fibrous mesoporous silica KCC-1, followed by condensation with 3-methoxy-2-hydroxybenzaldehyde (o-vanillin). The successfulness of functionalization and Schiff-base formation were confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The radially oriented fibrous channels of KCC-1 provide a highly accessible surface that remains available for interaction with the targeted ions even after chemical modification. This architecture facilitates rapid mass transfer and efficient utilization of binding sites, while the incorporated Schiff-base ligand introduces imine, phenolic, and methoxy donor groups capable of selectively and reversibly coordinating Ni(II) and Cd(II). The resulting balance between adsorption strength and desorption efficiency enables both effective metal capture and sorbent reusability. More importantly, the study demonstrates how KCC-1 can serve as a versatile nanosilica scaffold for the incorporation of tailored chelating ligands without sacrificing structural accessibility. The functionalized nanomaterial was evaluated as a dispersive solid-phase extraction (DSPE) sorbent coupled with inductively coupled plasma optical emission spectrometry (ICP-OES). Under optimized conditions, linear ranges of 0.035–50 μg L⁻¹ for Ni(II) and 0.058–50 μg L⁻¹ for Cd(II) were obtained, with limits of detection of 0.011 and 0.019 μg L⁻¹, respectively. The method exhibited excellent precision (relative standard deviation ≤ 3.6%) and recoveries of 92.00–98.83% in certified reference materaisl (NIST CRM 1643d), mineral water, tap water and synthetic wastewater. In addition, the nanochelator has retained more than 87% of its initial sorption efficiency after six adsorption–desorption cycles and showed minimal interference from common coexisting ions. These findings establish Van-KCC-1 as an efficient, selective, and reusable DSPE sorbent in the determination of trace-metals while highlighting the broader potential of fibrous mesoporous silica KCC-1 as a platform for the rational design of next-generation chelated nanomaterials. Full article

In this study, HC420LA steel plates joined by gas metal arc welding (MAG), manual laser welding (ML), and robotic laser welding (RL) were comparatively examined under heat input (HI) levels obtained from an active production line exhibiting weld defects. The effect of HI and welding method on mechanical properties, microstructural evolution, phase characteristics, and weld integrity was evaluated using tensile and hardness tests, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Weld imperfections were evaluated according to ISO 5817:2023(E) for MAG welds and BS EN ISO 13919-1:2019 for laser welds, and the corresponding quality levels were determined. The highest tensile strength (568 MPa) and elongation (23%) were achieved in RL welds at the lowest HI value (0.108 kJ/mm), with fracture occurring outside the weld region, indicating superior joint integrity and mechanical compatibility with the base metal. In contrast, MAG and ML welds exhibited a non-linear relationship between HI and ductility and tensile strength. ML welds showed higher hardness and reduced ductility due to the formation of harder transformation products, while MAG welds demonstrated a non-linear response associated with heat-affected zone (HAZ) coarsening. Heterogeneous phase distribution XRD analysis confirmed the presence of α-Fe-based phases and secondary alloyed structures, while EDS analyses revealed a relatively homogeneous distribution of the principal alloying elements within the weld regions and provided supporting evidence for the Mn₃O₄ oxide phase identified in the RL welds. SEM observations further demonstrated distinct microstructural transitions across the fusion zone (FZ) and HAZ, reflecting the influence of the welding process and heat input on weld evolution. The assessment of weld imperfections according to the relevant ISO standards showed that ML and RL welds satisfied Quality Level B, whereas MAG welds exhibited quality levels ranging from B to D, depending on the evaluated imperfection. These results indicate that equivalent HI values do not guarantee comparable weld quality or mechanical performance across different welding processes. The study provides insight into the relationship between heat input, weld quality, microstructural evolution, phase constitution, and mechanical performance in HSLA steels. Full article

Millimeter-wave (mm-wave) near-field imaging using frequency-modulated continuous wave (FMCW) radar has emerged as a pivotal technology for high-resolution applications, including security screening, non-destructive testing, and medical diagnostics. This review evaluates the performance and evolution of key imaging algorithms, categorized into spatial-domain and frequency-domain frameworks. We analyze the delay-and-sum (DAS) beamformer for its real-time utility and the back-projection algorithm (BPA) for its baseline phase precision and robust adaptability to irregular scanning trajectories. To address the high computational demands of standard spatial-domain processing, we examine fast alternatives such as the range migration algorithm (RMA). The exact RMA leverages Fourier-domain operations and Stolt coordinate mapping to achieve optimal computational scaling on uniform grids while preserving diffraction-limited spatial resolutions. Concurrently, we evaluate fast spatial-domain approximations, including Fast Back-Projection (Fast-BPA), which introduces localized Taylor-series expansions to linearize near-field range paths within sub-apertures, accelerating voxel reconstruction times at a reduced computational cost. Furthermore, this study explores advanced modifications designed to overcome physical and operational constraints, such as motion-compensated matched filtering (MF) to eliminate the “stop-and-go” assumption in continuous scanning, and sparse multiple-input multiple-output (MIMO) configurations to mitigate aliasing in undersampled environments. Comparative analysis reveals that while spatial-domain methods (DAS/BPA) generally offer higher robustness to non-uniform aperture perturbations, frequency-domain migration pathways (RMA) maximize the computational throughput required for large-volume three-dimensional (3D) reconstructions. The findings demonstrate that achievable resolution is primarily governed by signal bandwidth and aperture synthesis, though practical performance is often limited by calibration errors and computational overhead. Collectively, these advancements validate the potential of mm-wave FMCW systems to achieve sub-millimeter 3D imaging, bridging the gap between theoretical diffraction limits and real-world indoor sensing challenges. Full article

Porous silicate scaffolds represent a promising class of grafting materials for hard tissue engineering due to their superior bioactivity, adjustable degradation rates, and ability to stimulate both osteogenesis and angiogenesis. In this work, scaffolds based on an akermanite-targeted (Ca₂MgSi₂O₇) starting composition, including copper-doped variants, were synthesized using sol–gel and combustion routes, followed by 3D printing to achieve porous architectures with controlled pore size and interconnectivity. The powders were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermal analysis to evaluate their morphology, composition, and crystalline phases. The scaffolds were further assessed in terms of bioactivity by immersion in simulated body fluid (SBF), antibacterial activity, and in vitro cellular response. The results confirmed that copper doping enhanced antibacterial properties, while maintaining favorable biological behavior. Comparative analysis revealed differences between the two synthesis methods, with sol–gel providing more homogeneous structures and combustion leading to highly porous morphologies. These findings highlight copper-doped silicate scaffolds as promising candidates for bone tissue regeneration, combining architectural integrity with biological functionality. Full article

FeNi50 powder production for metallic magnetic cores faces challenges including low fine-powder yield and defects like hollow particles. This study employed cyclone atomization to prepare FeNi50 powder and systematically examined the effects of atomization pressure (1–6 MPa) through combined simulation, experiment, and theoretical analysis. Results show that increasing pressure reduces the average particle size (D50) from 80.7 μm to 27.9 μm and raises the fine powder yield (−500 mesh) from 19.4% to 50.0%, far exceeding that of close-coupled nozzle atomization (<10%). The powder particles are spherical/near-spherical with dense, non-hollow interiors. Higher pressure also increases the cooling rate, which blurs surface grain boundaries, refines grain structure, and induces single-crystal or amorphous characteristics in particles < 15 μm while suppressing N and O absorption. X-ray diffraction confirms the phase composition remains unchanged. These evolutions originate from three synergistic mechanisms: competition between solidification and spheroidization times, centrifugal and Magnus forces from swirling flow, and plastic-state droplet deformation imparting specific surface roughness. Cyclone atomization therefore proves a promising method for producing high-quality FeNi50 powder, suitable for large-scale manufacturing of high-performance magnetic powder cores. Full article

Ultra-High-Frequency (UHF) or Ultra-High-Resolution (UHR) seismic data can image in detail several meters below the seafloor, especially in shallow waters, where the assessment of the subsurface is critical for future nearshore construction. The method can detect the subsurface structure in detail in UHF seismic records, which are characterized by a high amount of diffracted energy. With the aim of enhancing the lateral continuity and resolution for the reflectors, we applied a multipath summation approach for the first time at such high frequencies. We employed strategies for separating the diffractions from the total signal in order to clearly take advantage of their AI-located apices for further velocity analysis. The derived Root Mean Square (RMS) velocity models did not prove to be sufficient for direct migration, something that the multipath summation using 2D stacking weights sufficiently solved. We combined the focused-energy seismic sections with the derived interval-velocity models and took into consideration the available borehole data to interpret the subsurface structure. We observed a sufficient enhancement of the P-wave refraction velocity models commonly derived in such investigations. This enhancement involved not only the resolution but also the additional indications of velocity reversals, which can be a severe drawback for the stability of offshore infrastructure due to the possibility of their hazardous origin, such as fractures, unstable bedrock, or voids. Full article

The growing volume of industrial waste and the need for sustainable material solutions drive the search for cost-effective fillers and energy-efficient processing methods for polymer composites. This study investigates the valorization of brick dust (BD), a fine ceramic waste, as a reinforcing filler for unsaturated polyester resin (UPR), combined with microwave (MW) treatment applied at different stages of composite fabrication. The brick dust was comprehensively characterized using laser diffraction, SEM, EDX, XRD, and FTIR, revealing an environmentally safe aluminosilicate powder with a mean particle size of 3–6 µm, plate-like morphology, and surface hydroxyl groups favorable for matrix interaction. The optimal filler content was found to be 50 phr, which increased flexural strength by 6.5%, flexural modulus by 134%, tensile strength by 11%, and impact strength by 40% compared to neat UPR. Among the MW strategies evaluated, post-curing of the fully polymerized composite for 120 s proved most effective, yielding further improvements in flexural strength (110 MPa, +34.1%), flexural modulus (8250 MPa, +49.7%), impact strength (13.8 kJ/m², +119%), and Shore D hardness (88). MW post-curing also increased the gel fraction from 95.0% to 97.8%, raised the thermal stability index (THRI) from 150.6 to 165.8, and reduced equilibrium water absorption from 0.62% to 0.47% with a reversibility index of 87.5%. Fracture surface analysis confirmed a transition from interfacial debonding to cohesive matrix failure, with ultra-thin polymeric veils replicating the scaly filler structure. These results demonstrate that microwave post-curing synergistically enhances the mechanical, thermal, and moisture-resistant properties of brick dust-filled polyester composites. Full article

Co- and Ni-doped mullite–spinel ceramics were synthesized via a sol–gel method followed by high-temperature sintering in order to investigate the influence of dopant type on the phase evolution, microstructure, and optical properties. X-ray diffraction analysis confirmed the formation of a multiphase system consisting of mullite and spinel phases, with a residual amorphous fraction, the amount of which decreases with increasing temperature. FTIR and Raman spectroscopy indicate progressive structural ordering of both spinel and aluminosilicate networks during thermal treatment, with differences in crystallization behavior between Co- and Ni-containing system. UV–Vis spectroscopy revealed characteristic absorption bands arising from d–d electronic transitions of Co²⁺ and Ni²⁺ ions in the ceramic matrix, reflecting differences in their local coordination environments and optical behavior. Colorimetric analysis showed that Co-doped samples exhibit intense blue coloration, whereas Ni-doped ceramics display greenish-blue hues. The temperature-dependent evolution of the L*, a*, and b* parameters correlate with structural changes. The results suggest that the type of additive influences the phase evolution and optical response in mullite–spinel ceramics, in agreement with structural and spectroscopic analyses. Full article