Search Results (1,847)

The ability of earth-abundant metals to serve as catalysts for the oxygen reduction reaction is of increasing importance given the prominence of this reaction in several emerging technologies. It is now recognized that both the primary and secondary coordination environments of these catalysts can be modulated to optimize their performance. In this present work, we describe two Co^II complexes [Co^II(PaPy₂Q)](OTf) (1) and [Co^II(PaPy₂N)](OTf) (2) that catalyze chemical and electrochemical dioxygen reduction. Both 1 and 2 contain Co^II centers in a N₅⁻ coordination environment, but 2 has a naphthyridine group that places a nitrogen atom in the secondary coordination sphere. Solid-state X-ray crystallography and solution-state spectroscopic measurements reveal that, apart from this second-sphere nitrogen in 2, complexes 1 and 2 have essentially identical properties. Despite these similarities, 2 performs the chemical reduction of dioxygen ~10-fold more rapidly than 1. In addition, 2 has an enhanced performance in the electrochemical reduction of dioxygen compared to 1. Both complexes yield a significant amount of H₂O₂ in the chemical reduction of dioxygen (>25%). The enhanced catalytic performance of 2 is attributed to the presence of the second-sphere nitrogen atom, which might enable the efficient protonation of cobalt–oxygen intermediates formed during turnover. Full article

The precise synthesis of non-precious metal single-atom electrocatalysts is crucial for enhancing the yield of highly active reactive oxygen species (ROSs). Conventional oxidation methods, such as Fenton or NaClO processes, suffer from poor efficiency, high energy demand, and secondary pollution. In contrast, heterogeneous electro-Fenton systems based on cascade oxygen reduction reactions (ORRs), which require low operational voltage and cause pollutant degradation through both direct electron transfer and ROS generation, have emerged as a promising alternative. Recent studies showed that carbon cathodes decorated with atomically dispersed transition metals can effectively integrate the excellent conductivity of carbon supports with the tunable surface chemistry of metal centers. However, the electronic structure of active sites intrinsically hinders the simultaneous achievement of high activity and selectivity in cascade ORRs. This review summarizes the advances, specifically from 2020 to 2025, in understanding the mechanism of cascade ORRs and the synthesis of transition metal-based single-atom catalysts in cathode electrocatalysis for efficient wastewater treatment, and discusses the key factors affecting treatment performance. While employing atomically engineered cathodes is a promising approach for energy-efficient wastewater treatment, future efforts should overcome the barriers in active site control and long-term stability of the catalysts to fully exploit their potential in addressing water pollution challenges. Full article

A square patch metasurface is designed, simulated, fabricated, and experimentally tested to investigate polarization characteristics quantitatively. The metasurface consists of one layer unit cell in the form of a square patch with one via and a lumped resistor, which is used for harvesting RF (radio frequency) energy. FR4 dielectric is used as a substrate supported by a metal ground plane. Polarization-dependent properties with specific surface current patterns and voltage dip are obtained when simulating under normal incidence of a plane wave. This characteristic results from changes in surface current conditions when the polarization angle is varied. A voltage dip appears at a specific polarization angle when the surface current pattern is symmetrical. This condition occurs when the position of the lumped resistor from the center of the patch is perpendicular to the linearly polarized incident electric field. A couple of 10 × 10 arrays with different resistor positions are fabricated and tested. The experimental results are in good agreement with the simulated results. The proposed design demonstrates a symmetric unit cell structure with one via and a resistor that exhibits polarization-dependent behavior for linear polarization. An asymmetric patch design is explored through both simulation and measurement to mitigate polarization dependence by suppressing the dip behavior, albeit at the expense of reduced absorption efficiency. This study provides a complete polarization analysis for both symmetric and asymmetric patch metasurfaces with a single via and a single lumped resistor, and introduces a predictive relation between the position of the resistor relative to the center of the patch and the resulting voltage dip behavior. Full article

Background: Peripancreatic collections (PPCs) are a frequent and severe complication of acute and chronic pancreatitis, as well as pancreatic surgery, often requiring interventions to treat and prevent infection, gastric obstruction, and other complications. Endoscopic ultrasound (EUS)-guided drainage has emerged as a minimally invasive alternative to surgical and percutaneous approaches, offering reduced morbidity and shorter recovery times. However, the effectiveness of EUS-guided drainage in post-surgical PPCs remains underexplored. Methods: This retrospective, single-center study evaluated the technical and clinical outcomes of EUS-guided drainage in patients with PPCs between October 2021 and December 2024. Patients were categorized as having post-pancreatitis or post-surgical PPCs. Technical success, clinical success, complications, recurrence rates, and the need for reintervention were assessed. Results: A total of 50 patients underwent EUS-guided drainage, including 42 (84%) with post-pancreatitis PPCs and 8 (16%) with post-surgical PPCs. The overall technical success rate was 100%, with clinical success achieved in 96% of cases. Lumen-apposing metal stents (LAMSs) were used in 84% of patients, including 7.1% as a dual-gate salvage strategy after the failure of double-pigtail drainage. The complication rate was 24%, with infection being the most common (16%). The recurrence rate was 25%, with no significant difference between post-pancreatitis and post-surgical cases. Patients with walled-off necrosis had a significantly higher reintervention rate (35%) than those with pseudocysts (18%; p = 0.042). Conclusions: EUS-guided drainage is a highly effective and safe intervention for PPCs, including complex post-surgical cases. The 100% technical success rate reinforces its reliability, even in anatomically altered post-surgical collections. While recurrence rates remain a consideration, EUS-guided drainage offers a minimally invasive alternative to surgery, with comparable outcomes in both post-pancreatitis and post-surgical patients. Future multi-center studies should focus on optimizing treatment strategies and reducing recurrence in high-risk populations. Full article

In this study, three new terphenyl-substituted NPN ligands bearing pyridyl groups, two phosphonites and one diaminophosphine, were synthesized and fully characterized. Their coordination chemistry with copper(I) was investigated using CuBr and [Cu(NCMe)₄]PF₆ as metal precursors, affording six mononuclear Cu(I) complexes, which were characterized using NMR spectroscopy and, in selected cases, single-crystal X-ray diffraction (SCXRD) analysis. The NPN ligands adopt a κ³-coordination mode, stabilizing the copper centers in distorted tetrahedral geometries. The catalytic performance of these complexes in the S-arylation of thiols with aryl iodides was evaluated. Under optimized conditions, complexes 2a and 2b exhibited excellent activity and broad substrate scope, tolerating both electron-donating and electron-withdrawing groups, as well as sterically hindered and heteroaryl substrates. The methodology also proved effective for aliphatic thiols and demonstrated high chemoselectivity in the presence of potentially reactive functional groups. In contrast, aryl bromides and chlorides were poorly reactive under the same conditions. These findings highlight the potential of well-defined Cu(I)–NPN complexes as efficient and versatile precatalysts for C–S bond formation. Full article

High-titanium steel contains an elevated titanium content, which promotes the formation of abundant non-metallic inclusions in molten steel at high temperatures, including titanium oxides, sulfides, and nitrides. These inclusions adversely affect continuous casting operations and generate substantial internal/surface defects in cast slabs, ultimately compromising product performance and service reliability. Therefore, stringent control over the size, distribution, and population density of inclusions is imperative during the smelting of high-titanium steel to minimize their detrimental effects. In this paper, samples of high titanium steel (0.4% Ti, 0.004% N) casting billets were analyzed by industrial test sampling and full section comparative analysis of the samples at the center and quarter position. Using the Particle X inclusions, as well as automatic scanning and analyzing equipment, the number, size, location distribution, type and morphology of inclusions in different positions were systematically and comprehensively investigated. The results revealed that the primary inclusions in the steel consisted of TiN, TiS, TiC and their composite forms. TiN inclusions exhibited a size range of 1–5 µm on the slab surface, while larger particles of 2–10 μm were predominantly observed in the interior regions. Large-sized TiN inclusions (5–10 μm) are particularly detrimental, and this problematic type of inclusion predominantly concentrates in the interior regions of the steel slab. A gradual decrease in TiN inclusion number density was identified from the surface toward the core of the slab. Thermodynamic and kinetic calculations incorporating solute segregation effects demonstrated that TiN precipitates primarily in the liquid phase. The computational results showed excellent agreement with experimental data regarding the relationship between TiN size and solidification rate under different cooling conditions, confirming that increased cooling rates lead to reduced TiN particle sizes. Both enhanced cooling rates and reduced titanium content were found to effectively delay TiN precipitation, thereby suppressing the formation of large-sized TiN inclusions in high-titanium steels. Full article

Background/objectives: The increasing prevalence of multidrug-resistant (MDR) bacteria, particularly Klebsiella pneumoniae, calls for the development of new antimicrobial agents. This study investigates a series of fluorinated azolium salts and their rhodium(I) complexes for antibacterial activity against clinical and reference strains of K. pneumoniae. Methods: Eleven fluorinated azolium salts and their corresponding Rh(I) complexes (22 compounds total) were synthesized and tested against several K. pneumoniae strains, including three MDR clinical isolates (U–13685, H–9871, U–13815) and ATCC reference strains. Minimum inhibitory concentrations (MICs) were determined. In silico ADMET analyses were conducted to evaluate intestinal absorption, oral bioavailability, Caco-2 permeability, carcinogenicity, solubility, and synthetic accessibility. Results: Among the Rh(I) complexes, Rh–1, Rh–3, and Rh–11 showed activity against the three MDR isolates (MIC = 62.5–250 µg/mL), while Rh–1, Rh–4, Rh–6, and Rh–11 were active against all ATCC strains (MIC = 3.9–250 µg/mL). The corresponding azolium salts displayed weak or no activity, highlighting the critical role of the metal center. ADMET predictions indicated that most Rh complexes had good intestinal absorption, and all except Rh–3, Rh–4, and Rh–9 were predicted to be orally bioavailable. Compounds Rh–1 to Rh–7 showed Caco-2 permeability, and all were classified as non-carcinogenic. Rh–8 to Rh–11 exhibited lower solubility and synthetic accessibility. Conclusions: The results underscore the potential of fluorinated Rh(I) complexes as antibacterial agents against MDR K. pneumoniae, with Rh–1 and Rh–11 emerging as promising leads based on activity and favorable predicted pharmacokinetics. Full article

As manufacturing demands for challenging-to-machine metallic materials continue to evolve, the performance of cutting tools has emerged as a critical limiting factor. The synergistic application of micro-texture and coating in cutting tools can improve various properties. For the processing of existing micro-texture, because of the fast cooling and heating processing method of laser, there are defects such as remelted layer stacking and micro-cracks on the surface after processing. This study introduces a preheating-assisted technology aimed at optimizing the milling performance of textured coated tools. A milling test platform was established to evaluate the performance of these tools on titanium alloys under thermally assisted conditions. The face-centered cubic response surface methodology, as part of the central composite design (CCD) experimental framework, was employed to investigate the interaction effects of micro-texture preparation parameters and thermal assistance temperature on milling performance. The findings indicate a significant correlation between thermal assistance temperature and tool milling performance, suggesting that an appropriately selected thermal assistance temperature can enhance both the milling efficiency of the tool and the surface quality of the titanium alloy. Utilizing the response surface methodology, a multi-objective optimization of the textured coating tool-preparation process was conducted, resulting in the following optimized parameters: laser power of 45 W, scanning speed of 1576 mm/s, the number of scans was 7, micro-texture spacing of 130 μm, micro-texture diameter of 30 μm, and a heat-assisted temperature of 675.15 K. Finally, the experimental platform of optimization results is built, which proves that the optimization results are accurate and reliable, and provides theoretical basis and technical support for the preparation process of textured coating tools. It is of great significance to realize high-precision and high-quality machining of difficult-to-machine materials such as titanium alloy. Full article

The model explicitly incorporates boundary conditions that account for the complex interplay between sections experiencing varying degrees of reduction. This interaction significantly influences the overall deformation behavior and force loading. The control effect is associated with boundary conditions determined by the unevenness of the compression, which have certain quantitative and qualitative characteristics. These include additional loading, which is less than the main load, which implements the process of plastic deformation, and the ratio of control loads from the entrance and exit of the deformation site. According to this criterion, it follows from experimental data that the controlling effect on the plastic deformation site occurs with a ratio of additional and main loading in the range of 0.2–0.8. The next criterion is the coefficient of support, which determines the area of asymmetry of the force load and is in the range of 2.00–4.155. Furthermore, the criterion of the regulating force ratio at the boundaries of the deformation center forming a longitudinal plastic shear is within the limits of 2.2–2.5 forces and 1.3–1.4 moments of these forces. In this state, stresses and deformations of the plastic medium are able to realize the effects of plastic shaping. The force effect reduces with an increase in the unevenness of the deformation. This is due to a change in height of the longitudinal interaction of the disparate sections of the strip. There is an appearance of a new quality of loading—longitudinal plastic shear along the deformation site. The unbalanced additional force action at the entrance of the deformation source is balanced by the force source of deformation, determined by the appearance of a functional shift in the model of the stress state of the metal. The developed theory, using the generalized method of an argument of functions of a complex variable, allows us to characterize the functional shift in the deformation site using invariant Cauchy–Riemann relations and Laplace differential equations. Furthermore, the model allows for the investigation of material properties such as the yield strength and strain hardening, influencing the size and characteristics of the identified limit state zone. Future research will focus on extending the model to incorporate more complex material behaviors, including viscoelastic effects, and to account for dynamic loading conditions, more accurately reflecting real-world milling processes. The detailed understanding gained from this model offers significant potential for optimizing mill roll designs and processes for enhanced efficiency and reduced energy consumption. Full article

The fabrication and application of single-site heterogeneous reaction centers are new frontiers in chemistry. Single-site heterogeneous reaction centers are analogous to metal centers in enzymes and transition-metal complexes: they are charged and decorated with ligands and would exhibit superior reactivity and selectivity in chemical conversion. Such high reactivity would also result in significant response, such as a band gap or resistance change, to approaching molecules, which can be used for sensing applications. As a proof of concept, the electronic structure and reaction pathways with NO and NO₂ of Au(I) fragments dispersed on phosphorene (Pene) were investigated with first-principle-based calculations. Atomic-deposited Au atoms on Pene (Au₁-Pene) have hybridized Au states in the bulk band gap of Pene and a decreased band gap of 0.14 eV and would aggregate into clusters. Passivation of the Au hybrid states with -OH and -CH₃ forms thermodynamically plausible HO-Au₁-Pene and H₃C-Au₁-Pene and restores the band gap to that of bulk Pene. Inspired by this, HO-Au₁-Pene and H₃C-Au₁-Pene were examined for detection of NO and NO₂ that would react with -OH and -CH₃, and the resulting decrease of band gap back to that of Au₁-Pene would be measurable. HO-Au₁-Pene and H₃C-Au₁-Pene are highly sensitive to NO and NO₂, and their calculated theoretical sensitivities are all 99.99%. The reaction of NO₂ with HO-Au₁-Pene is endothermic, making the dissociation of product HNO₃ more plausible, while the barriers for the reaction of CH₃-Au₁-Pene with NO and NO₂ are too high for spontaneous detection. Therefore, HO-Au₁-Pene is not eligible for NO₂ sensing and CH₃-Au₁-Pene is not eligible for NO and NO₂ sensing. The calculated energy barrier for the reaction of HO-Au-Pene with NO is 0.36 eV, and the reaction is about thermal neutral, suggesting HO-Au-Pene is highly sensitive for NO sensing and the reaction for NO detection is spontaneous. This work highlights the potential superior sensing performance of transition-metal fragments and their potential for next-generation sensing applications. Full article

Metal chelation to bioactive small molecules is a well-established strategy to enhance the biological activity of the resulting complexes. Among the widely explored structural motifs, the combination of prominent metal centers with naturally inspired derivatives has attracted considerable attention. One such promising platform is the flavone scaffold, derived from flavonoids and studied since ancient times. Flavones are plant-derived compounds known for their diverse biological activities and health benefits. They exhibit significant structural variability, primarily through backbone modifications such as hydroxylation. Importantly, coordination of metal ions to hydroxylated flavone cores often improves their natural bioactivities, including anticancer and antimicrobial effects. In this review, we summarize transition metal complexes incorporating hydroxyflavone (OH–F) ligands reported over the past 15 years. We provide a concise overview of synthetic approaches and structural characterization, with a particular emphasis on coordination modes (e.g., maltol-type, acetylacetonate-type, catechol-type, and others). Furthermore, we discuss biological evaluation results, especially anticancer and antimicrobial studies, to highlight the therapeutic potential of these complexes. Finally, we suggest directions for the future development of metal-based agents bearing hydroxyflavone moieties through several critical points in terms of the accuracy, reproducibility, and relevance of biological studies involving metal-based compounds. Full article

The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C₂₊) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol conversion on single metal atoms anchored on graphitic carbon nitride (TM/g–CN). We showed that these metal atoms stably coordinate with edge N sites of g–CN to form active catalytic centers. Screening 20 TM/g–CN candidates, we identified V/g–CN and Zn/g–CN as optimal catalysts: both exhibit low free-energy barriers (<0.50 eV) for the key ^*CO hydrogenation steps and facilitate C–C coupling via an Eley–Rideal mechanism with a negligible kinetic barrier (~0.10 eV) to yield ethanol at low limiting potentials, which explains their superior COER performance. An analysis of d-band centers, charge transfer, and bonding–antibonding orbital distributions revealed the origin of their activity. This work provides theoretical insights and useful guidelines for designing high-performance single-atom COER catalysts. Full article

We studied the adsorption thermodynamics and mechanism behind the binding of nitric oxide (NO) in the interior surfaces and structural fragments of the high metal center density microporous Metal-Organic Framework (MOF) CPO-27-Cu, by gas sorption, at a series of temperatures. For the purpose of comparison, we also measured the corresponding CO₂ adsorption isotherms, and as a result, the isosteric heats of adsorption for the two studied adsorptives were derived, being in the range of 12–15 kJ/mol for NO at loadings up to 0.5 NO molecules per formula unit (f.u.) of the bare compound (C₄O₃HCu), and 23–25 kJ/mol CO₂ in the range 0–1 CO₂ per f.u. Microscopically, the mode of NO binding near the square pyramid Cu(II) centers was directly accessed with the use of in situ NO gas adsorption X-ray Absorption Spectroscopy (XAS). Additionally, during the vacuum/temperature activation of the material and consequent NO adsorption, the electronic state of the Cu-species was monitored by observing the corresponding X-ray Near Edge Spectra (XANES). Contrary to the previously anticipated chemisorption mechanism for NO binding at Cu(II) species, we found that at slightly elevated temperatures, under ambient, but also cryogenic conditions, only relatively weak physisorption takes place, with no evidence for a particular adsorption preference to the coordinatively unsaturated Cu-centers of the material. Full article

Biofloc technology (BFT), traditionally centered on feed supplementation and water purification in aquaculture, harbors untapped multifunctional potential as a sustainable resource management platform. This review systematically explores beyond conventional applications. BFT leverages microbial consortia to drive resource recovery, yielding bioactive compounds with antibacterial/antioxidant properties, microbial proteins for efficient feed production, and algae biomass for nutrient recycling and bioenergy. In environmental remediation, its porous microbial aggregates remove microplastics and heavy metals through integrated physical, chemical, and biological mechanisms, addressing critical aquatic pollution challenges. Agri-aquatic integration systems create symbiotic loops where nutrient-rich aquaculture effluents fertilize plant cultures, while plants act as natural filters to stabilize water quality, reducing freshwater dependence and enhancing resource efficiency. Emerging applications, including pigment extraction for ornamental fish and the anaerobic fermentation of biofloc waste into organic amendments, further demonstrate its alignment with circular economy principles. While technical advancements highlight its capacity to balance productivity and ecological stewardship, challenges in large-scale optimization, long-term system stability, and economic viability necessitate interdisciplinary research. By shifting focus to its underexplored functionalities, this review positions BFT as a transformative technology capable of addressing interconnected global challenges in food security, pollution mitigation, and sustainable resource use, offering a scalable framework for the future of aquaculture and beyond. Full article

The first-principles calculation method was used to study doping elements with atomic numbers in the range of 23–30 (V–Zn) to form a single-atomic-spin nanochannel in a CoTiSb matrix. In a Ni-Sb single-atomic chain with high spin polarization and hole electrical conductivity, V-Sb, Mn-Sb, Fe-Sb, and Co-Sb single-atom chains have 100% spin polarization, indicating that a supercell containing the central atom chain has typical half-metal characteristics, and in the CoTiSb matrix, is centered on very small single-spin nanochannel forms. Using doping elements with atomic numbers between 23 and 27 (V-Co), the total magnetic moment of the supercell is constantly increasing, but the total magnetic moment of the Ni-doped supercell (Ni-Ti supercell) reduces, and a Cr-Ti supercell has an equal total magnetic moment. Doping elements Cu and Zn have atomic numbers higher than the range. Although the material of the nanochannel retains ferromagnetic properties, the spin polarization rate is reduced, and the material no longer has half-metallic properties. Full article