Search Results (61)

The electrochemical stability of redox-active polymers based on Ni(II)–Salen complexes is of critical importance for their application as electrode materials for supercapacitors and lithium-ion batteries. This study presents a systematic analysis of the influence of fluoride, chloride, and bromide anions on the redox behavior of two polymeric films: poly[Ni(Salen)] and sterically protected poly[Ni(Saltmen)]. Using cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and X-ray photoelectron spectroscopy (XPS), we identify two distinct degradation mechanisms: (1) axial coordination of halide ions to the Ni(II) center followed by demetallation, which disrupts the conjugated system and reduces conductivity, and (2) oxidative halogenation of the ligand. In the presence of chloride ions, both poly[Ni(Salen)] and poly[Ni(Saltmen)] lose approximately 70% of their initial capacity over 50 cycles, indicating progressive electrochemical degradation. In contrast, both polymers demonstrate high electrochemical stability in bromide-containing electrolytes, retaining most of their capacity under identical conditions. Fluoride coordinates without compromising redox performance, serving as a model for electrochemically inert ligands. The results highlight the critical role of both electrolyte composition and ligand design in ensuring the long-term stability of nickel–Salen polymers in energy storage devices. Full article

Hexafluoroethane and 1,1,1,3,3,3-hexafluoropropane (abbreviated as HFC-236fa and R-116, respectively, referred to as C₂F₆ and C₃H₂F₆ based on their molecular formulas) were selected as the object to study the corrosion effects of gas fire-extinguishing agents on different metal materials in the storage state. Typical metal materials used in storage containers including 304 stainless steel, Q235 carbon steel, 6061 aluminum alloy, H59 brass, and T2 copper were subjected to full-immersion corrosion experiments under simulated storage conditions with high-pressure and alternating high–low temperature cycles. High-definition cameras, a scanning electron microscope (SEM), high-precision electronic balances, an energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) were used to explore the corrosion characteristics. The chemical reactions and mechanisms were analyzed. The results indicate the following: (1) A thin corrosion layer appears on the surface of the metal with varying degrees of severity but low prevalence. (2) The corrosion rates of C₂F₆ and C₃H₂F₆ were comparable and varied in the following order: 6061 aluminum alloy > Q235 carbon steel > H59 brass > 304 stainless steel > T2 copper. (3) C₃H₂F₆ is slightly higher than C₂F₆ in all corrosion rate values. (4) The corrosion of metal materials is mainly attributed to the reaction between metal elements and the F-containing groups produced by the cleavage of C₂F₆ and C₃H₂F₆. The generated metal halides in turn catalyze the cleavage of C₂F₆ and C₃H₂F₆. This catalytic effect may be positively correlated with the reactivity of the metal element. (5) The higher corrosive activity of C₃H₂F₆ compared to C₂F₆ is attributed to the ease of C–C bond cleavage, catalyzed by metal halogens. This study provides theoretical insights into the corrosion ability of halogenated alternatives as a replacement for halon-based fire extinguishers. Full article

Eco-friendly flame retardants are becoming a popular alternative to traditional fire retardants, many of which contain toxic halogens. These modern additives, which are based on phosphorus, nitrogen, or silicon compounds, minimize the emission of harmful gases during combustion, making them safer for the environment and human health. This study aimed to synthesize and analyze poly(vinyl chloride) (PVC) composites using a newly synthesized hybrid fire retardant, boehmite derivative (aluminium dibutyl phosphonate), as an environmentally friendly additive. The fire-retardant properties of chitosan, which is derived from the natural biopolymer chitin, have also been tested. The chemical structure of the synthesized compounds was confirmed using ATR/FTIR spectroscopy and SEM-EDX analysis. Next, PVC-based dry blends were prepared with the addition of a stabilizer, plasticiser, chalk, and selected flame retardants (aluminium dibutyl phosphonate or chitosan) at concentrations of 10 wt%, 30 wt%, and 50 wt%, resulting in homogeneous materials intended for evaluating fire performance, thermal stability (DSC, TGA), and mechanical resistance. Full article

As an eco-friendly flame-retardant additive, magnesium hydroxide (MH) is widely employed in low-smoking, halogen-free polymer materials due to its environmentally benign nature. In order to enhance flame retardancy performance, the modified MH was modified with tetrakis(hydroxymethyl)phosphonium sulfate (THPS) by a one-pot hydrothermal method. The resulting morphology was characterized using scanning electron microscopy (SEM), and it shows the dispersion of nanometer particles and almost no aggregation. The X-ray photoelectron spectroscopy (XPS) along with Raman spectroscopy show that the THPS is connected with the Mg(OH)₂ by chemical bond. The sample was incorporated into ethylene–vinyl acetate (EVA) to evaluate the flame retardancy was assessed via limiting oxygen index (LOI) and vertical burning tests (UL-94). The results show that THPS modified MH effectively enhanced the flame retardancy, achieving a V-0 rating and an LOI value of 31.3%. In addition, the composites retain good mechanical integrity. The thermal analysis with TGA and DTG shows the formation of the MgO decomposition product, along with water vapor and phosphorus-containing radicals released by modified MH in the combustion process, forming a strong flame-retardant protective layer. In addition, the maximum smoke density of EVA/MHP-3 composite was 155.4, lower than 411.3 for EVA/MH, with a 62.2% reduction in total smoke production. The result shows that THPS is effective for improving the flame-retardant efficiency of inorganic metal hydroxide in polymer composites. Full article

This study explores the use of agricultural waste rice husk powder (RH) as a sustainable alternative to the petrochemical-derived carbon source, pentaerythritol (PER), in expandable flame retardants. RH is combined with halogen-free ammonium polyphosphate (APP), which serves as both an acid and a gas source. The resulting APP/RH system is incorporated into bio-based thermoplastic polyurethane (Biobased TPU) to prepare a halogen-free, flame-retardant composite material consistent with circular economy principles and environmental sustainability. The optimal APP-to-RH ratio in bio-based TPU was determined to be 2:1, with the best flame-retardant performance observed in the composite containing 20 wt% APP/RH. This formulation achieved a limiting oxygen index (LOI) of 27% and a UL-94 V-0 rating, indicating excellent flame resistance. Thermogravimetric analysis (TGA) showed a significant increase in char residue—from 0.51 wt% in pure TPU to 26.1 wt%—demonstrating improved thermal stability. Further characterization using cone calorimetry, thermogravimetric analysis–Fourier transform infrared spectroscopy (TGA-FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy confirmed that the addition of APP/RH significantly enhances the flame-retardant properties of the TPU composite. Consequently, the application of TPU in construction materials can be advanced through improved fire safety performance and alignment with sustainability goals. Full article

Lead-free A₂ZrX₆ “defect” perovskites hold significant potential for many optoelectronic applications due to their stability and tunable properties. Extending a previous work, we present a first-principles density functional theory (DFT) study, utilizing PBE and HSE06 functionals, to systematically investigate the impact of A-site cation and X-site halogen substitutions on the structural and electronic properties of these materials. We varied the A-site cation, considering ammonium, methylammonium, dimethylammonium, trimethylammonium, and phosphonium, and the X-site halogen, trying Cl, Br, and I. Our calculations reveal that both these substitutions significantly affect the band gap and the lattice parameters. Increasing A-site cation size generally enlarges the unit cell, while halogen electronegativity directly correlates with the band gap, yielding the lowest values for iodine-containing systems. We predict a broad range of band gaps (from ~4.79 eV for (PH₄)₂ZrCl₆ down to ~2.11 eV for MA₂ZrI₆ using HSE06). The (PH₄)₂ZrX₆ compounds maintain cubic crystal symmetry, unlike the triclinic of the ammonium-derived systems. Finally, our calculations show that the MA cation yields the smallest band gap among the ones studied, a result that is attributed to its size and the charges of the hydrogen atoms attached to nitrogen. Thus, our findings offer crucial theoretical insights into A₂ZrX₆ structure–property relationships, demonstrating how A-site cation and halogen tuning enables control over electronic and structural characteristics, thus guiding future experimental efforts for tailored lead-free perovskite design. Full article

This study presents a novel environmentally-friendly process for the selective extraction and enrichment of DHA/EPA-containing phospholipids (PL-DHA/EPA) from krill oil. The methodology leverages differential crystallization behavior between phospholipids and triacylglycerols in ethanolic solutions, exploiting their distinct freezing point thresholds to achieve precise fractionation. Response surface methodology optimization identified optimal extraction parameters: liquid-to-material ratio of 6:1 (v/w), freezing temperature of −20 °C, freezing duration of 25 h, and rotary evaporation temperature of 45 °C, yielding a final product with 39.40% PL-DHA/EPA content. Principal component analysis revealed substantial overlap in confidence ellipses among extraction methodologies, indicating effective preservation of core phospholipid signatures from the parent krill oil while maintaining critical structural characteristics and molecular species distribution. Comprehensive analysis of phospholipid fractions and heatmap analysis revealed distinctive molecular profiles compared to conventional organic solvent extraction, with selective enrichment of EPA-containing phospholipids, particularly PC-EPA and PI-EPA species. The green extraction method demonstrated comparable oxidative stability to conventional approaches, with superior protection against secondary oxidation as evidenced by significantly lower anisidine values. This sustainable approach achieves effective phospholipid enrichment while substantially reducing environmental impact through elimination of halogenated solvents, addressing the critical need for environmentally conscious technologies in marine lipid processing with potential applications in nutraceutical and functional food industries. Full article

Contact electrification (CE), or triboelectrification, is an electron transfer phenomenon occurring at the interface between dissimilar materials due to differences in polarity, holding significant research value in tribology. The microscopic mechanisms of CE remain unclear due to the complex coupling of multiple physical processes. Recently, with the rise of triboelectric nanogenerator (TENG) technology, solid–liquid contact electrification has demonstrated vast application potential, sparking considerable interest in its underlying mechanisms. Emerging experimental evidence indicates that at water–polymer CE interfaces, the process involves not only traditional ion adsorption but also electron transfer. Halogen-containing functional groups in the solid material significantly enhance the CE effect. To elucidate the microscopic mechanism of water–polymer CE, this study employed first-principles density functional theory (DFT) calculations, simulating the interfacial electrification process using unit cell models of water contacting polymers. We systematically and quantitatively investigated the charge transfer characteristics at interfaces between water and three representative polymers with similar backbones but different halogen-functionalized (F, Cl) side chains: fluorinated ethylene propylene (FEP), polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE), focusing on evaluating halogen’s influence and mechanism on interfacial electron transfer. The results reveal that electron transfer is primarily governed by the energy levels of the polymer’s lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO). Halogen functional groups modulate the material’s electron-donating/accepting capabilities by altering these frontier orbital energy levels. Consequently, we propose that the critical strategy for polymer chemical modification resides in lowering the LUMO energy level of electron-accepting materials. This study provides a novel theoretical insight into the charge transfer mechanism at solid–liquid interfaces, offers guidance for designing high-performance TENG interfacial materials, and holds significant importance for both the fundamental theory and the development of advanced energy devices. Full article

Quinazolinones, a class of nitrogen-containing heterocyclic compounds, occupy a crucial position in medicinal chemistry and materials science due to their significant application potential. In recent years, the catalytic asymmetric synthesis of axially chiral quinazolinones has emerged as a prominent research area, driven by their prospective applications in the development of bioactive molecules, design of chiral ligands, and fabrication of functional materials. This review comprehensively summarizes recent advancements in the catalytic asymmetric synthesis of axially chiral quinazolinones, with a particular focus on the construction strategies for the three major structural types: the C–N axis, N–N axis, and C–C axis. Key synthetic methodologies, including atroposelective halogenation, kinetic resolution, condensation–oxidation, and photoredox deracemization, are discussed in detail. In addition, the review provides an in-depth analysis of the applications of various catalytic systems, such as peptide catalysis, enzymatic catalysis, metal catalysis, chiral phosphoric acid catalysis, and others. Despite the substantial progress made thus far, several challenges remain, including the expansion of the substrate scope, enhanced control over stereoselectivity, and further exploration of practical applications, such as drug discovery and asymmetric catalysis. These insights are expected to guide future research towards the development of novel synthetic strategies, the diversification of structural variants, and a comprehensive understanding of their biological activities and catalytic functions. Ultimately, this will foster the continued growth and evolution of this rapidly advancing field. Full article

Polyamide-based glass fibre-reinforced composites are extensively used in electrical and automotive applications due to their excellent mechanical, thermal, and electrical properties. However, prolonged exposure to high temperatures can lead to significant degradation, affecting their long-term performance and reliability. This study investigates the thermal ageing behaviour of polyamide 6,6 composites containing halogenated flame retardants used for electrical applications. The objective of this research is to evaluate the extent of degradation through accelerated ageing tests and to develop an Arrhenius-type ageing model to predict the long-term performance of these materials. This study examines the effects of thermal ageing at temperatures between 160 and 210 °C on flexural properties and explores the underlying degradation mechanisms. Results indicate that short-term exposure to high temperatures can enhance flexural strength due to annealing effects, which are eventually outweighed by thermal oxidation and increased crystallinity, leading to an increase in brittleness. The derived Arrhenius model, with an activation energy of 93 kJ/mol, predicts a service life of approximately 25 years at 80 °C, but a significantly shorter one at 130 °C. These findings underscore the importance of considering thermal ageing effects in the design and application of PA66 composites in high-temperature environments. Full article

Biogas usually contains volatile organic compounds such as terpenes, siloxanes, halogenated hydrocarbons, ketones, alcohols, furans and esters whose presence in the biogas is highly dependent on the feedstock. These trace components can affect the integrity of the materials they come into contact with, e.g., equipment, pipelines and engines, and their presence in the gas may pose health, safety and environmental risks. Understanding the composition of gases is a prerequisite to ensure the correct function of gas infrastructure, appliances and vehicles. This study examined how volatile organic compound (VOC) content in biogas varies depending on the feedstock and evaluated the efficiency of different upgrading processes in removing VOCs. The data, primarily collected in Sweden, include biogases produced in digesters and landfills. The selection of VOCs included in this study was based on extensive analysis of samples collected from numerous biogas and biomethane industrial facilities over an extended period, providing a comprehensive overview of VOC composition. The conducted research is intended to serve as a basis for more systematic studies on the influence of process parameters and feedstock composition on the formation of VOCs. The data have multiple potential uses, including predicting which VOCs would be found in biomethane for a given feedstock and upgrading techniques. Additionally, these data can also be used in standardization discussions to assess the plausibility of the proposed limit values and the need to regulate additional compounds. Full article

This paper presents the results of quantum-chemical modeling performed by the Density Functional-Based Tight Binding (DFTB) method to investigate the change in the band structure of hybrid materials based on carbon nanotubes and unsubstituted, tetra-, or octa-halogen-substituted zinc phthalocyanines upon the adsorption of ammonia molecules. The study showed that the electrical conductivity of these materials and its changes in the case of interaction with ammonia molecules depend on the position of the impurity band formed by the orbitals of macrocycle atoms relative to the forbidden energy gap of the hybrids. The sensor response of the hybrids containing halogenated phthalocyanines was lower by one or two orders of magnitude, depending on the number of substituents, compared to the hybrid with unsubstituted zinc phthalocyanine. This result was obtained by calculations performed using the nonequilibrium Green’s functions (NEGF) method, which demonstrated a change in the electrical conductivity of the hybrids upon the adsorption of ammonia molecules. The analysis showed that in order to improve the sensor characteristics of CNT-based hybrid materials, preference should be given to those phthalocyanines in which substituents contribute to an increase in HOMO energy relative to the unsubstituted macrocycles. Full article

Photocatalysis offers a powerful approach for water purification from toxic organics, hydrogen production, biosolids processing, and the conversion of CO₂ into useful products. Further advancements in photocatalytic technologies depend on the development of novel, highly efficient catalysts and optimized synthesis methods. This study aimed to develop a laser synthesis technique for bismuth oxyhalide nanoparticles (NPs) as efficient and multifunctional photocatalysts. Laser ablation of a Bi target in a solution containing halogen salt precursors, followed by laser plasma treatment of the resulting colloid, yielded crystalline bismuth oxyhalides (Bi_xO_yX_z, where X = Cl, Br, or I) NPs without the need for additional annealing. The composition, structure, morphology, and optical properties of the synthesized Bi_xO_yX_z (X = Cl, Br, I) NPs were characterized using XRD analysis, electron microscopy, Raman spectroscopy, and UV-Vis spectroscopy. The effect of the halogen on the photocatalytic activity of the double oxides was investigated. The materials exhibited high photocatalytic activity in the degradation of persistent model pollutants like Rhodamine B, tetracycline, and phenol. Furthermore, the Bi_xO_yX_z NPs demonstrated good efficiency and high yield in the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). The obtained results highlight the promising potential of this laser synthesis approach for producing high-performance bismuth oxyhalide photocatalysts. Full article

Phenazine natural products are a class of colored nitrogen-containing heterocycles produced by various microorganisms mainly originating from marine and terrestrial sources. The tricyclic ring molecules show various chemical structures and the decorating groups dedicate extensive pharmacological activities, including antimicrobial, anticancer, antiparasitic, anti-inflammatory, and insecticidal. These secondary metabolites provide natural materials for screening and developing medicinal compounds in the field of medicine and agriculture due to biological activities. The review presents a systematic summary of the literature on natural phenazines in the past decade, including over 150 compounds, such as hydroxylated, O-methylated, N-methylated, N-oxide, terpenoid, halogenated, glycosylated phenazines, saphenic acid derivatives, and other phenazine derivatives, along with their characterized antimicrobial and anticancer activities. This review may provide guidance for the investigation of phenazines in the future. Full article

Cationic porous organic polymers have a unique advantage in removing radioactive iodine from the aqueous phase because iodine molecules exist mainly in the form of iodine-containing anions. However, halogen anions will inevitably be released into water during the ion-exchange process. Herein, we reported a novel and easy-to-construct zwitterionic hypercrosslinked polymer (7AIn-PiP)-containing cationic pyridinium-type group, uncharged pyridine-type group, pyrrole-type group, and even an electron-rich phenyl group, which in synergy effectively removed 94.2% (456 nm) of I₂ from saturated I₂ aqueous solution within 30 min, surpassing many reported iodine adsorbents. Moreover, an I₂ adsorption efficiency of ~95% can still be achieved after three cyclic evaluations, indicating a good recycling performance. More importantly, a unique dual 1,3-dipole was obtained and characterized by ¹H/¹³C NMR, HRMS, and FTIR, correlating with the structure of 7AIn-PiP. In addition, the analysis of adsorption kinetics and the characterization of I₂@7AIn-PiP indicate that the multiple binding sites simultaneously contribute to the high affinity towards iodine species by both physisorption and chemisorption. Furthermore, an interesting phenomenon of inducing the formation of HIO₂ in unsaturated I₂ aqueous solution was discovered and explained. Overall, this work is of great significance for both material and radiation protection science. Full article