Search Results (1,039)

Dopamine is a key neurotransmitter and neuromodulator that regulates many critical brain functions. Accurate monitoring of its level is essential for neuroscience as well as the diagnosis and treatment of many brain diseases. In this work, we developed a new electrochemical sensor, comprising phosphorus-doped graphitic carbon nitride (P-g-C₃N₄) and zeolitic imidazolate framework 67 (ZIF-67), for dopamine detection. In this composite electrode material, ZIF-67 provides numerous adsorption and sensing sites, while P-g-C₃N₄ enhances overall electrical conductivity and stability. Cyclic voltammetry tests reveal the redox behavior of dopamine at the surface of the composite electrode across various pH values and scan rates. Using differential pulse voltammetry, the sensitivity and selectivity of this dopamine sensor were assessed, identifying a limit of detection of 0.39 nM. Further successful quantification of dopamine in urine samples suggests the potential practical use of this new composite electrochemical sensor for detecting dopamine and/or other neurotransmitters. Full article

Developing effective metal-free electrocatalysts for acidic hydrogen evolution is challenging because both catalytic activity and electronic conductivity must be optimized simultaneously. Here, h-BN/carbon nano-onion (CNO) hybrid electrocatalysts were synthesized by integrating layered hexagonal boron nitride with conductive carbon nano-onions to generate accessible heterointerfaces for the hydrogen evolution reaction (HER). Structural characterization by XRD, SEM/TEM, and STEM-EDS confirmed intimate contact between h-BN sheets and quasi-spherical CNO domains. Similarly, XPS revealed B–N-rich frameworks with interfacial B–C/C–N surface environments and oxygen-associated defect sites. Among the prepared compositions, the h-BN/CNO20 eletrocatalyst exhibited the best apparent HER performance in 0.5 M H₂SO₄, delivering an overpotential of ~270 mV at 5 mA cm⁻² and a Tafel slope of 76 mV dec⁻¹, along with stable chronoamperometric behavior for 15 h. The improved electrocatalytic activity is due to the enhanced charge transport through the CNO network, suppression of h-BN restacking, increased exposure of interfacial sites, and charge redistribution across B–N/C heterojunctions. These findings identify h-BN/CNO20 as the optimum composition within this series and demonstrate that heterointerface engineering between boron nitride and curved graphitic nanocarbons is a promising strategy for developing metal-free HER electrocatalysts. However, further validation using a non-Pt counter electrode is necessary to confirm intrinsic catalytic activity. Full article

The development of multilayer coatings based on titanium carbides and nitrides remains one of the most active areas in materials science, owing to their ability to markedly enhance wear resistance and extend the service life of machine components. Particular interest is currently focused on tailoring conventional TiN/TiCN architectures through alloying metal additions. In this study, the tribological and mechanical performance of aluminum- and zirconium-doped TiN/TiCN multilayer coatings deposited by direct-current magnetron sputtering onto 41Cr4 steel was investigated. The morphology, elemental distribution, and phase constitution of the multilayer coatings were examined. It is shown that increasing the number of bilayers from two to four in TiN/TiCN–based multilayer coatings leads to improved tribomechanical characteristics. It was determined that zirconium provides a more pronounced beneficial effect than aluminum. The four-bilayer TiZrN/TiZrCN coating simultaneously exhibited the lowest coefficient of friction (0.11) and wear rate (10⁻⁶ mm³ m⁻¹ N⁻¹) at a hardness of 16.4 GPa. Full article

Secondary aluminum dross (SAD) is classified as hazardous waste (HW48) due to its content of toxic (e.g., heavy metals, fluorides) and highly reactive phases (e.g., aluminum nitride, AlN). This review systematically synthesizes the sources, heterogeneous composition, and environmental risks of SAD, and critically evaluates state-of-the-art hydrometallurgical and pyrometallurgical detoxification and resource-utilization technologies. Comparative, mechanism-oriented analyses are used to elucidate the respective advantages, limitations, and scalability of wet versus thermal routes. Particular emphasis is placed on the migration, transformation, and ultimate fate of key hazardous species (AlN, fluorides, chlorides, and heavy metals) during treatment and product valorization. An integrated hydro–pyro nexus is conceptualized as synergistic hybrid processing that transcends the trade-offs between efficiency, energy consumption, and product purity that currently limit standalone technologies. Emerging hybrid process concepts, advanced additives, and circular-economy-oriented product pathways are evaluated to address current technological bottlenecks. Finally, critical knowledge gaps and research priorities are identified to accelerate safe, low-carbon, and high-value utilization of SAD. Full article

The study presents a comprehensive first-principles investigation of the structural, electronic, and magnetic properties of rocksalt scandium nitride (ScN) and its Cr- and Mn-doped derivatives using spin-polarized density-functional theory within the GGA + U (U_Cr = 3.5 eV, U_Mn = 2.7 eV) and HSE06 frameworks. Pristine ScN crystallizes in the cubic Fm$\bar{3}$m structure and exhibits narrow-gap semiconducting behavior, with an indirect band gap of 0.82 eV obtained from hybrid-functional calculations, in excellent agreement with reported theoretical values. Substitutional doping with Cr and Mn introduces localized 3d states near the Fermi level, driving a transition toward spin-polarized metallic or half-metallic behavior accompanied by robust ferromagnetism. Density-of-states and band-structure analyses reveal that magnetism and charge transport in the doped systems are dominated by exchange-split transition-metal 3d states hybridized with N-2p orbitals. Total energy calculations confirm ferromagnetic ground states for both Cr- and Mn-doped ScN, with Mn substitution yielding stronger exchange stabilization and higher magnetic moments. Magnetocrystalline anisotropy energies, evaluated using the force-theorem approach, are found to be negligibly small, indicating weak anisotropy consistent with the moderate spin–orbit coupling strength in ScN-based nitrides. Nevertheless, symmetry breaking around dopant sites gives rise to a finite Dzyaloshinskii–Moriya interaction, leading to weak spin canting and non-collinear magnetic tendencies. The interplay between magnetic exchange coupling, spin–orbit interaction, and local inversion symmetry breaking positions of Cr- and Mn-doped ScN as promising dilute magnetic semiconductors with tunable spin polarization and chiral magnetic interactions, offering a viable platform for nitride-based spintronic and magneto-electronic applications. Full article

Hexagonal boron nitride (h-BN) has been widely applied in catalysis. Nevertheless, most research has focused on using h-BN as a substrate to anchor active transition metals, without probing the intrinsic activity of h-BN vacancies. In this work, we investigated the stability and catalytic activity of different h-BN vacancies. We found that B-terminated vacancies are more likely to be exposed under static conditions. The N_v, BN₂, and BN₃ vacancies show intermediate reaction energies for CH₄ activation. Although the B–N pair over the BN₂ vacancy model has the lowest barrier for CH₄ activation, the negative reaction energy could lead to a high potential for surface poisoning. Interestingly, the unsaturated B–B pair over N_v is a promising site for C–H bond activation. Further COHP analysis implies that the high C–H bond homolytic cleavage activity of the B–B pair arises from its relatively weak interaction, which can promote H insertion. Full article

Degradation of volatile organic compounds (VOCs) by environmentally friendly methods remains a challenging issue. Photothermal catalysis, as an emerging green catalytic technology, merges the benefits of both thermal catalysis and photocatalysis, presenting itself as a viable strategy for VOC degradation. However, achieving higher catalytic performance by reasonably designing the synthetic route of catalyst carriers remains difficult. In this study, crystalline carbon nitride material, poly(triazine imide) (PTI), was prepared using a unique molten salt synthesis method and employed as a support for Pt to construct an exceptional photothermal catalyst. In a continuous-flow system under Xe lamp irradiation with external temperature control, toluene was efficiently degraded at a high rate of nearly 100% under low Pt content (0.31 wt%) and a relatively low operational temperature condition (143 °C). As a carrier of noble metals, PTI material exhibited a larger specific surface area and fewer structural defects, resulting in more efficient toluene conversion and mineralization. The joint action of photocatalysis and thermocatalysis synergistically facilitated the efficient generation of active species and accelerated charge transfer, thereby significantly boosting toluene catalytic oxidation. These findings provide valuable guidance for designing and optimizing photothermal catalysts for the removal of VOCs. Full article

To address the lack of suitable glass systems for silicon nitride (Si₃N₄) surface metallization, which requires high wettability and thermal stability, and robust bonding between the copper layer and the ceramic substrate, a novel Bi₂O₃-TeO₂-B₂O₃-CuO glass system was developed. This study systematically investigated the influence of Bi₂O₃ concentration, glass properties, optimized paste composition, and brazing mechanism using phase analysis, microstructural characterization, particle size statistics, thermal analysis, and tensile testing. An optimal glass composition containing 20 mol% Bi₂O₃ was identified, exhibiting high thermal stability (ΔT = 224 °C) and a coefficient of thermal expansion of 9.63 × 10⁻⁶ °C⁻¹. At a brazing temperature of 750 °C, the glass demonstrated excellent wettability with a contact angle of 27°. A conductive paste comprising 94 wt% Cu and 6 wt% glass yielded a thick film with a minimum resistivity of 6.25 μΩ·cm and a maximum tensile strength of 25.2 MPa. Mechanism analysis revealed that the superior wettability drives the liquid glass phase to form a thin intermediate layer that significantly reinforces adhesion. These findings contribute to the research and development of subsequent novel glass systems with superior performance. Full article

Stimulating electronic transitions and promoting exciton dissociation are key to enhancing the photocatalytic performance of polymer carbon nitride (PCN). Herein, a controllable synthesis strategy based on supramolecular self-assembly and mild salt melting crystallization has been developed, successfully preparing carbon nitride-based photocatalytic materials with tunable crystal phase composition. The mixed crystal phases effectively induced significant n→π* electronic transition, expanding the material’s light response range to the near-infrared region (700 nm). Meanwhile, the homojunction promoted the efficient separation of photogenerated carriers through the built-in electric field. Under visible-light excitation, this material exhibits excellent selective catalytic performance, over 99% for the oxidation and removal of H₂S into elemental sulfur. This synergistic mechanism of crystal phase engineering in regulating electronic structure and interface charge dynamics provides a new material design strategy for efficient non-metallic photocatalysts. Full article

Ammonia has emerged as a strategically advantageous hydrogen carrier; however, its efficient decomposition using conventional solid catalysts remains technically challenging from an industrial standpoint, particularly in terms of long-term stability and large-scale implementation. In this study, we propose a strategy for ammonia cracking by utilizing Sn-based molten metal alloys in a bubble column reactor, which provides a sintering-resistant and thermally efficient catalytic platform. Among various candidate transition metals, the Sn-Co alloy exhibited the most superior catalytic performance, demonstrating a significant reduction in the apparent activation energy to 52.6 kJ/mol. To the best of our knowledge, this study provides the first experimental evidence of the catalytic role of molten metals in the ammonia decomposition process. Structural characterization confirmed that the molten alloy maintains its metallic state without the formation of nitrides, verifying the function of the molten metal as an active catalyst rather than a sacrificial reagent. This work offers a new catalytic approach that addresses the requirements for the commercialization of ammonia cracking through improved scalability and chemical durability. Full article

Laser powder bed fusion has attracted increasing attention for the production of metallic substrates intended for surface functionalization by advanced physical vapor deposition coatings. This study investigates the influence of the substrate manufacturing route on the performance of titanium–aluminum–silicon nitride-coated AISI 316L stainless steel, with particular emphasis on substrates produced by laser powder bed fusion. Conventionally manufactured and additively manufactured AISI 316L substrates were coated with a titanium–aluminum–silicon nitride layer using high-power impulse magnetron sputtering. The substrates were characterized by tensile testing and microhardness measurements, while coating thickness and uniformity were evaluated using the crater ball method. The mechanical integrity of the coating–substrate system was assessed by progressive load scratch testing. The additively manufactured substrate exhibited a significantly higher yield strength (411 MPa) compared to the conventionally manufactured material (257 MPa), together with increased microhardness. The titanium–aluminum–silicon nitride coating showed a uniform thickness of 4.47 µm and a well-defined coating–substrate interface. Scratch tests revealed a delayed onset of coating damage on additively manufactured substrates, with the transition to severe adhesive failure occurring at higher normal loads compared to the conventionally manufactured substrate. These results demonstrate that AISI 316L stainless steel produced by laser powder bed fusion provides a mechanically robust substrate for titanium–aluminum–silicon nitride coatings deposited by high-power impulse magnetron sputtering, with favorable coating response under progressive loading conditions. Full article

Catalytic materials are central to the advancement of hydrogen generation technologies, playing a pivotal role in enabling sustainable, carbon-neutral energy systems. Hydrogen can be produced via electrochemical water splitting, thermochemical reforming, or photocatalysis—each imposing unique performance requirements on catalysts in terms of activity, selectivity, stability, and efficiency. While traditional noble metals (e.g., platinum, ruthenium, iridium) provide benchmark catalytic activity, their widespread use is hindered by scarcity, high cost, and limited long-term durability. Consequently, researchers have increasingly focused on earth-abundant alternatives such as transition metals (Ni, Co, Fe, Mo), alloys, metal oxides, carbides, sulfides, nitrides, and carbon-based systems. Among these, two-dimensional materials, particularly the MXene family, have attracted significant attention due to their metallic conductivity, layered structure, and tunable surface chemistry. These features enable rapid charge transfer and abundant active sites, making MXenes and related nanostructured catalysts promising for both the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) across a wide range of electrochemical conditions. Parallel efforts have integrated novel semiconductors, plasmonic nanomaterials, and hybrid heterostructures to improve the efficiency of solar-to-hydrogen energy conversion. This paper reviews the main types of catalytic materials used in hydrogen production, explains their design strategies and structure–performance relationships, and discusses key engineering challenges such as integrating renewable energy sources, scaling up manufacturing, and ensuring long-term durability in real-world systems. Future research goals are also highlighted, including the development of affordable non-noble catalysts, enhancing catalyst stability through surface and defect engineering, and coupling hydrogen production with circular economy principles, all of which are essential to making hydrogen generation more efficient, scalable, and cost-effective as the world transitions to clean and sustainable energy. Full article

The global population explosion and accelerated industrialization have led to an increasing shortage of fossil fuels and environmental contamination, underscoring the urgent need to develop innovative energy storage technologies to improve energy utilization efficiency. As pivotal components in thermal energy storage (TES) systems, phase change materials (PCMs) enable spatiotemporal matching between thermal energy supply and demand through latent heat absorption and release during phase transitions. Organic PCMs are considered ideal candidates for thermal energy storage due to their high energy storage density, stable phase transition temperature, low supercooling, and negligible phase separation. However, inherent drawbacks such as low thermal conductivity, liquid leakage, limited light absorption, and lack of functionality have hindered their widespread application in advanced thermal management systems. Herein, we systematically summarize cutting-edge functionalization strategies for PCMs, progressing from conventional methods like thermal conductive particle blending and microencapsulation to the emerging design of 3D porous thermally conductive skeletons, including metal foams, boron nitride aerogels, carbon-based aerogels, and MXene aerogels. These frameworks not only enhance thermal transport via continuous conductive pathways and impart shape stability through capillary encapsulation but also, when integrated with photo-thermal, electro-thermal, and magneto-thermal conversion properties, enable broad applications in solar photo-thermal/photo-thermo-electric conversion, thermal management of electronics and batteries, building efficiency, and wearable thermal regulation. The review further addresses current challenges and future directions, highlighting scalable 3D framework fabrication, the shift to active thermal management, and innovative applications beyond conventional domains. By establishing a microstructure–property–application correlation, this work provides valuable insights for developing next-generation high-performance multifunctional phase change composites. Full article

Quantum dots (QDs) have drawn a lot of attention as photocatalytic materials due to the growing need for environmentally friendly wastewater treatment technologies. Among these, carbon-based QDs, including graphene oxide quantum dots (GOQDs), graphitic carbon nitride (g-C₃N₄), and carbon quantum dots (CQDs), have exceptional optical, electronic, and surface characteristics that increase their suitability for degrading pollutants when exposed to sunlight or visible light. These composites are better at transferring charges, staying stable in light, and breaking down pollutants. Metal-based QDs like ZnO and CdS also have strong photocatalytic activity, but their sustainability remains a concern due to the potential release of toxic ions when they corrode in light. The green synthesis approach addresses these challenges. Using natural extracts, like polyphenols from tea leaves, to biofunctionalize surfaces has been shown to reduce toxicity and improve photocatalytic performance. Green synthesis using renewable precursors solves problems with toxicity, resource depletion, and environmental pollution, which supports a low-impact and circular technological approach. This study examines recent developments in the making, modifying, and use of QD-based photocatalysts in the environment, with a focus on CQD/g-C₃N₄ hybrid systems. Future research should focus on making green, non-toxic, regenerable, and highly active carbon-based QDs for safe large-scale water treatment. Full article

Accurate radiation thermometry of real objects critically depends on knowledge of surface emissivity, which is rarely known a priori and often varies with surface condition, temperature, and environment. Although theoretical models for spectral emissivity evaluation exist, their practical validation under application-relevant conditions remains limited. In this study, spectral and radiometric emissivity evaluation methods are compared on metallic samples up to 350 °C. The spectral method derives effective emissivity from spectroscopy-measured spectral emissivity using instrument-specific spectral sensitivity (responsivity), while the radiometric method evaluates emissivity directly from radiance measurements using a radiation thermometer and a reference contact temperature. The radiometric method is treated as an application-level reference. Stable and homogeneous chromium nitride (CrN)-coated samples show good agreement between the two methods, whereas raw metals and polysiloxane-coated samples highlight practical limitations related to sample surface instability and inhomogeneity. The results demonstrate that spectral emissivity evaluation is valid in practice when its underlying method assumptions are fulfilled, while radiometric evaluation remains preferable for in situ infrared thermometry. Full article