Search Results (12,842)

Carcinine is an imidazole dipeptide with potent antioxidant and antiglycation properties, although its chemical synthesis currently relies on severely environmentally harmful processes. In this work, a multi-enzyme cascade biotransformation system comprising 4′-phosphopantetheinyl transferase and non-ribosomal peptide synthetase was constructed. To overcome the limitations arising from stochastic spatial distribution and suboptimal mass transfer associated with independent enzymes, a fusion protein strategy was adopted. The two enzymes were fused via a flexible genetic linker within plasmid pET28a-SFP-L-Ebony, which enabled robust soluble expression in Escherichia coli. Concurrently, the endogenous peptidase genes (pepA, pepB, pepD, and pepN) were systematically knocked out using CRISPR/Cas9-mediated gene editing. This quadruple protease-deficient strain (designated SFP-L-Ebony-ΔpepABDN) effectively suppressed product degradation. Subsequent optimization revealed that optimal catalytic performance occurred at 25 °C and pH 7.0. The highest biotransformation efficiency was achieved using 15 g/L crude enzymes, in the presence of 2 mM ATP and 10 mM MgCl₂. Through a fed-batch substrate feeding strategy in a 50 mL reaction system, the final carcinine titer reached 7.0 g/L after 48 h. This study, therefore, provides an efficient and sustainable technological pathway for the green biomanufacturing of carcinine as well as other high-value dipeptides. Full article

Explosive detonation is a high-speed and high-energy chemical-physical transformation process that rapidly generates high-temperature and high-pressure gases as well as shock waves. These energies are released intensely in a short time, exhibiting extremely strong destructive power. When these high-temperature and high-pressure gases and shock waves act on the surface of combustibles, they can instantly peel off the hot core on the surface, disrupting the conditions necessary for sustaining the combustion reaction and thereby achieving a fire-extinguishing effect. However, to attain this application goal, it is essential to select explosive materials with both high energy density and low sensitivity. In this study, DFTB-MD (Density Functional Tight-Binding Molecular Dynamics) and DFT (Density Functional Theory) methods were employed to systematically investigate the thermal decomposition process of benzotrifuroxan (BTF)/1,3,5-trinitrobenzene (TNB) cocrystal nanoparticles under high-temperature conditions. Our simulations reveal, for the first time, that the thermal decomposition mechanism of BTF/TNB cocrystal nanoparticles is strongly size-dependent: the 1.8 nm particles exhibit earlier ring-opening of BTF due to the higher surface-to-volume ratio, while the 2.2 nm particles show superior structural stability and lower molecular diffusivity. Meanwhile, increasing temperature from 2100 K to 2400 K shifts the dominant initial decomposition pathway from C–NO₂ cleavage in TNB to ring rupture in BTF. These findings provide atomic-scale theoretical insights into the design and application of BTF/TNB cocrystal nanoparticles for explosion-based fire suppression. Full article

This study employs density functional theory and quantum chemical calculations to investigate the gas-phase nucleation and growth mechanisms during chemical vapor deposition of silicon carbide. Based on thermodynamic stability evaluations of large clusters under various configurations, the lowest-energy ground-state structure was determined. The Gibbs free energy (ΔG) calculations of pure silicon clusters (Si_n), single-carbon silicon clusters (Si_nC), and double-carbon silicon clusters (Si_nC₂) were conducted at different temperatures. The findings reveal that silicon atoms promote cluster growth. The special 2D-to-3D configurational transition attenuates the reaction’s spontaneity. During the initial nucleation stage, the system tends to form Si_nC; however, as the size increases, it evolves into the more stable Si_nC₂. This study reveals gas-phase cluster formation at the atomic scale, providing a theoretical foundation for suppressing detrimental gas-phase nucleation. Full article

Polyester–cotton (PES/CO) blends represent one of the most widely used textile classifications globally, yet their fibre-to-fibre recycling remains technically challenging due to the chemical dissimilarity of the two fibres. Existing reviews typically address textile recycling in broad terms, leaving a gap in critically evaluating the specific separation chemistries, recovered-fraction quality, and industrial maturity of PES/CO recycling routes. This review addresses that gap by providing a focused and comparative assessment of technologies designed for PES/CO fractionation. The paper analyses both polyester-removal and cellulose-removal routes, covering depolymerisation (hydrolysis, glycolysis, methanolysis, aminolysis), dissolving systems (NMMO, ionic liquids, DES, cold alkaline), and enzymatic or acid-based degradation. Each route is evaluated using technical criteria including fraction purity, cellulose degree of polymerisation, polyester monomer recovery, fibre quality, chemical consumption and energy requirement, solvent recovery, reaction conditions, and scalability. The review finds that chemical depolymerisation of PES and selective dissolution of cellulose currently show the strongest potential for high-quality fibre-to-fibre recycling, particularly when solvent recovery systems are integrated. However, significant barriers remain, including incomplete fraction purity, degradation of cellulose DP, limited recovery of high-quality polyester intermediates, high chemical consumption, and insufficient industrial-scale demonstrations. Overall, this review provides a differentiated and critical synthesis of PES/CO recycling technologies, clarifying their readiness levels and outlining the key scientific and industrial challenges that must be addressed to enable circularity in blended textile waste streams. Full article

The processing of bee products has recently become more frequent due to the rapidly growing market and demand for healthy, natural, and functional food. Therefore, bee products, and above all honey, while maintaining the reputation of healthy and natural foods, become carriers of various additives. Their consumption without proper control, or not declaring their presence in the composition, may pose a significant hazard to human health and life. This study was based on data mining with the use of all accessible RASFF records. They were formatted to analyze all chemical hazards that have occurred in bee honey and have been noted by EU countries to support swift reaction by food safety authorities since 2014. Within 10 food categories presenting 13,295 records, 93 records applied to bee products, including 79 records that referred to honey, 65% (n = 51) of which related to chemical hazards. PDE-5 inhibitors, i.e., sildenafil and tadalafil, were identified 14 times during the last 6 years and were the second most numerous group of hazards in honey and honey-based products after VMPs. The periodically published results of market sample tests and the continuing trend of RASFF notifications of these compounds in honey and honey-based products may suggest an iceberg phenomenon that requires frequent and thorough inspections. Full article

Ascorbate (AsA), or vitamin C, is a central redox metabolite that functions as an antioxidant, enzyme cofactor, and electron donor. Its cellular function depends not only on biosynthesis or dietary uptake, but also on rapid recycling from its oxidized forms, monodehydroascorbate (MDHA) and dehydroascorbate (DHA). This requirement is especially evident in high-demand systems such as plant chloroplasts, which face continuous photosynthetic reactive oxygen species (ROS) production under illumination, and human neutrophils, which accumulate millimolar ascorbate to withstand NADPH oxidase-driven oxidative bursts in pathogen defense. Here, we revisit ascorbate recycling from a sulfur-centered perspective. Historical studies of plant, animal, and solution-chemistry pathways show that many DHA-reducing systems converge on sulfur chemistry, including glutathione (GSH), cysteine-dependent enzymes, H₂S, and modified thiols. We propose that ascorbate recycling is organized as a multilayered system in which nonenzymatic reactions are accelerated by enzymes, localized within cellular or extracellular compartments, and integrated with broader NAD(P)H-, glutathione-, sulfur-, and diet-dependent redox networks. Within this framework, the AsA/DHA couple can be viewed as a molecular redox capacitor that buffers transient oxidative pressure. Reactive sulfur species (RSS), including persulfides and polysulfides, represent chemically plausible but experimentally unresolved contributors to DHA reduction. Full article

High-performance ammonia (NH₃) sensors play a critical role in environmental protection and noninvasive medical diagnosis. This work reports a new NH₃ sensor based on Au-microsphere-decorated polyaniline (PANI) manufactured by a precise in situ inkjet printing method on a MEMS micro-hotplate. The in situ oxidative polymerization of aniline was performed directly on the MEMS platform using AuCl₃ as a bifunctional oxidant and precursor, with a hierarchical morphology of microspheres (~750 nm) and nanorods (~250 nm). Reduced from Au³⁺ in the polymerization reaction, Au microparticles achieve substantial catalytic promotion by virtue of chemical sensitization and spillover effect. The optimized Au–PANI MEMS sensor exhibits a superlative response of 201% toward 1 ppm NH₃ at room temperature, with an ultra-low theoretical limit of detection (LOD) of 0.42 ppb. Furthermore, the device demonstrates rapid response/recovery kinetics (76 s/72 s), exceptional selectivity against common interfering gases (SO₂, CO, H₂, etc.), and robust long-term stability with high response retention over two months. This research provides a scalable, cost-effective strategy for the mass production of miniaturized, high-sensitivity gas sensors for industrial and healthcare applications. Full article

Considering the various applications where detection is required—whether for industrial or medical purposes—providing cost-efficient, stable, and highly selective solutions remains challenging. Different industries require hydrogen detectors, because this gas has the potential to serve as a clean and versatile energy carrier; therefore, precise monitoring and feedback in such systems are of enormous importance. Simultaneously, the medical field is developing new therapeutic methods using hydrogen as a medical gas, while also utilizing it as a biomarker in exhaled breath for various gastric diseases. In this paper, a ZnO-based gas sensor, doped with Ag nanoparticles produced via the Solution Chemical Synthesis (SCS) method, was coated with a thin polymer film of poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) PV4D4 via initiated Chemical Vapor Deposition (iCVD). The results are promising: at a relatively high operating temperature of 350 °C, the sensor showed its highest registered response to H₂ gas (up to 23%). Compared to other gases studied at the same temperature, the sensor also showed potential for detecting 2-propanol, n-butanol, and ethanol, albeit with lower responses. Based on the dynamic response analysis, the fastest reaction time was also recorded at the highest operating temperature, thus showing versatile possibilities for using the specified detector. Full article

There is an urgent and persistent need to design efficient and sustainable methods to manufacture chemicals on a large scale. Heterogeneous photocatalysts use light to drive organic reactions and offer high recyclability and improved efficiencies for chemical synthesis. However, a detailed study of these photocatalysts using standard laboratory analytical techniques is challenging due to their poor solubility. Successful application of heterogeneous photocatalysts in the chemical industry requires the development of a robust analytical technique that can be used as a predictive and scalable tool for their photocatalytic performance. Herein, we report a simple approach that uses the color of cotton-bound heterogeneous photocatalysts as a potential indicator of their performance. These photocatalysts were synthesized by covalently attaching perylene-based molecular photocatalysts to the surface of cotton using amino-substituted triethoxysilane as the linker. Colorimetry coupled with NMR analysis revealed two important findings: (i) cotton-bound photocatalysts catalyzed sulfide oxidation to sulfoxide under blue-light illumination, and (ii) a general relationship was observed between color intensity and catalytic performance, with darker samples generally exhibiting faster reaction rates. These findings suggest that color may serve as a simple and rapid tool for assessing photocatalyst performance. Future studies will focus on enhancing the reproducibility of photocatalyst binding procedures and validating the color–performance relationships in a wider range of color intensities of the cotton-bound photocatalysts. Full article

Electrochemical CO₂ reduction reactions (CO₂RR) offer a viable approach to mitigating anthropogenic CO₂ while simultaneously generating value-added chemicals. Among diverse electrocatalyst classes, metal–organic framework (MOF)-based materials have been extensively explored owing to their excellent tunability of chemical structure, high surface area, and the ability to tailor the coordination/electronic environment of active centers. This state-of-the-art review provides a critical assessment of recent progress in the development of pristine Cu-based MOFs, Cu MOF-derived catalysts, and hybrid Cu@MOFs for the selective production of C₁ products such as CO, CH₄, and formate/formic acid. Theoretical investigations into the roles of the copper center, ligands, pore structures, and interfacial effects reveal that product selectivity is influenced by more than just the oxidation state of Cu sites. Mixed-valence Cu⁺/Cu⁰ junctions, defect-rich surfaces, conductive frameworks, and coordination site tuning constitute fundamental design strategies for steering CO₂ reduction pathways. In addition to electrocatalytic performance, this review emphasizes the importance of life cycle assessment (LCA). Current studies identify electricity demand, separation steps, and operational lifetime as the dominant environmental impact factors in LCA analyses. Combining molecular-level catalyst design with systems-level sustainability considerations, this review highlights key challenges and future prospects for advancing Cu-MOF electrocatalysts toward efficient and sustainable C₁ formation from CO₂. Full article

It is crucial to develop advanced fluorescence sensing platforms for precise detection of metal pollutants in environmental monitoring. However, traditional fluorescent probes are often limited by aggregation-caused quenching (ACQ). In contrast, clusterization-triggered emission (CTE) probes, based on non-conjugated systems, exhibit excellent photostability by relying on spatial clusterization to restrict molecular motion. Crab shells, an abundant aquatic waste, are rich in chitin (20–30%). Following deacetylation, chitin is converted into chitosan, a biocompatible and biodegradable biopolymer with excellent potential for chemical modification. In this study, a novel chitosan-based CTE fluorescent probe (CS-FA) was synthesized via a facile cross-linking condensation reaction between chitosan and formaldehyde. This process successfully restricts intramolecular motion and promotes the tight clustering of electron-rich heteroatoms, thereby activating the CTE mechanism. The resultant CS-FA probe exhibits strong and stable blue fluorescence and demonstrates high selectivity and sensitivity toward Fe³⁺ in aqueous media. In the concentration range of 10–100 µM, the fluorescence intensity decreases linearly with the Fe³⁺ concentration, yielding a competitive limit of detection (LOD) of 0.52 µM. Mechanistically, the specific coordination between Fe³⁺ and the cross-linked polymer provides a dominant non-radiative decay pathway, leading to significant fluorescence quenching. Ultimately, this work not only proposes an innovative strategy for constructing sensitive and biomass-derived probes for Fe³⁺ monitoring but also broadens the high-value utilization pathways of marine waste, thereby providing a sustainable waste-to-resource strategy. Full article

This work focuses on the combustion characteristics and kinetics of three building timber organic solid wastes (BTOSW)—China fir, Eucalyptus wood, and Pine wood—aiming to provide theoretical and data support for the thermal conversion and energy utilization of construction-derived woody biomass. Thermogravimetric analysis (TGA) reveals that all three materials exhibit two-stage combustion behavior: volatile combustion at low temperatures (<320 °C) and char combustion at high temperatures (320–500 °C). Increasing the heating rate shifts the decomposition peaks to higher temperature zones, reflecting the combined effects of thermal lag and shortened reaction time. Kinetic analysis shows that the correlation coefficients (R²) calculated by different models are all greater than 0.97, with the first-order chemical reaction model (O1) demonstrating the highest goodness-of-fit for Pine wood (R² = 1.000) and Eucalyptus wood (R² = 0.995), indicating that homogeneous chemical reactions dominate the combustion process. The initial combustion temperatures of China fir, Eucalyptus wood, and Pine wood are 256 °C, 262 °C, and 270.9 °C, respectively, with flammability indices of 1.08, 1.46, and 1.15 and comprehensive combustion characteristic indices of 2.71 × 10⁻², 1.26 × 10⁻², and 1.75 × 10⁻² °C⁻²min⁻¹, respectively. This work provides important theoretical support for both the energy utilization of timber-framed buildings waste and the fire protection design and flame retardancy of timber-framed buildings, contributing to the development of scientific fire prevention measures and the preservation of this architectural heritage. Full article

Batteries, especially useful for portable instruments, are the most widely used alternative to direct current. Their operating principle is based on irreversible or reversible chemical reactions, which are called primary (non-rechargeable) or secondary (rechargeable), respectively. Primary batteries never completely discharge and their residual charge depends on the energy demand of the instrument in which they are used. Even if correctly disposed of, therefore, and with the possibility of recycling the constituent materials and purchasing and using consciously, only 2 of the 3Rs, namely “Recycle” and “Reuse”, are respected; recovering the residual charge would also allow compliance with the last of the 3Rs, namely “Reduce”. Direct energy recovery methods have been proposed but the simplest method to “reduce”, analogously to what is done with secondary batteries, remains being recharging, which, unfortunately, is a risky operation, as it can cause the battery to explode or leak corrosive solution. Following our previous research, in which we proposed a method for measuring the residual charge of alkaline batteries, we now propose a method for charging the batteries whose residual charge we measured in our previous work. In this research, a hand-built external circuit, Arduino UNO R3, was used to generate the charging pulses and as a controller and measuring instrument and an Open-Source protocol for the recharging process. The results demonstrated the feasibility of the method, as the voltage of 50% of the batteries increased and, further, only 18% of the batteries leaked and none exploded. Full article

Based on comparative experiments conducted on conventional Portland cement (OPC) systems, ferraluminate cement (FAC) systems, and FAC–fly ash (FA) composite systems, this study systematically investigates the ion evolution in pore solutions and the transformation of hydration products, as well as the compositional and microstructural evolution of the passive film formed on steel reinforcement surfaces under simulated pore solution conditions and natural passivation conditions. The results show that: ① FAC and FA-mixed systems produce different product types from OPC in the early stage (mainly AFt/AFm, C–(A)–S–H), thereby altering the pH and the evolution of the main ion concentration in the pore solution. ② An appropriate amount of FA (10%) refines the pore structure through pozzolanic reaction, enhances low-frequency electrochemical impedance, and facilitates the evolution of the steel passive film toward a more favorable composition; however, excessive incorporation (20%) induces a “dilution effect” and reduces the early-age densification rate, which is ultimately detrimental to long-term corrosion resistance. ③ The passive film exhibits a characteristic chemical gradient evolution, comprising an outer Fe³⁺-enriched phase and an inner Fe²⁺-enriched phase. Its thickness and the Fe²⁺/Fe³⁺ ratio are significantly influenced by the chemical environment of the pore solution (pH, SO₄²⁻, Al³⁺, Fe³⁺, etc.), which plays a decisive role in the protective efficiency of the steel reinforcement. These findings establish the intrinsic relationship between pore solution chemistry, hydration product evolution, and passive film development, providing new mechanistic insight into the passivation behavior of reinforcing steel in FAC–FA systems. Based on these findings, key guidelines for the proportioning and microstructural–electrochemical design of ferroaluminate cement are proposed, providing scientific support for the durability-oriented application of FAC–based materials in aggressive environments. It should be noted that the beneficial effect of incorporating 10 wt.% FA is limited to the optimization of FAC–based systems and should not be interpreted as indicating superior overall corrosion resistance compared with OPC. Full article

The flammability of building materials and products is expressed by the reaction to fire class according to the European standard EN 13501-1. However, the procedures described in this technical standard and in the related test standards do not fully reflect the physical and chemical principles of combustion. Especially in the area of lower classes B–F, the methodology is based on empirical principles, which makes it relatively very complicated to use the test results in the development of new insulation materials and predict their behaviour. This paper presents the initial phase of research that approaches combustion from a building-physics perspective at the scale of the fibre microstructure. In the case of insulation materials based on polymer fibres (very often based on recycled textile fibres), the situation is very complicated because, in most cases, the reaction to fire is given by combination of physical and chemical processes under contact of material with the flame. Rather than proposing a complete predictive model, this study formulates the basic governing relationships and reports the first experimental results, which will serve as the basis for a comprehensive model developed within the follow-up research. Single-flame-source tests (EN ISO 11925-2), combined with microstructural, calorimetric and airflow-resistivity measurements, established basic relationships between the observed flame behaviour and parameters such as fibre type, thickness and bulk density. The main observation is a clear ignition/no-ignition dichotomy between primary fibres (which melted and withdrew from the flame without igniting) and recycled fibres (which ignited), showing that neither the heat of combustion alone nor a purely physical description is sufficient—both physical and chemical aspects must be considered. Full article