Search Results (532)

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

Biodiesel is a sustainable and promising alternative energy source produced from renewable raw materials using various methods. One effective approach is simultaneous esterification and transesterification, which relies on suitable catalysts that can be either homogeneous or heterogeneous. Homogeneous catalysts (acid or base) offer high activity but are corrosive and difficult to recover, necessitating energy-intensive processes such as aqueous quenching and neutralization, which can lead to soap formation and stable emulsions. By comparison, heterogeneous catalytic systems overcome many of these challenges due to their ease of recovery, reusability, and simplified product separation, which collectively enhance economic viability and environmental sustainability. This review highlights recent progress in the application of zeolite-based solid catalysts for biodiesel synthesis, with particular emphasis on their use in converting waste cooking oil and other low-cost feedstocks, including non-edible oils, non-food biomass sources, algal resources, and genetically engineered microorganisms. Key factors such as catalytic activity, selectivity, catalyst loading, and reusability are discussed, highlighting the advantages of zeolites due to their unique crystal structure, high thermal stability, and ease of product recovery. Overall, this review underscores the challenges and opportunities in zeolite-based catalysis to provide a comprehensive understanding of its potential to enhance the efficiency and scalability of biodiesel production. Full article

Biomineralization has recently emerged as a highly effective strategy for enzyme immobilization. Zeolitic imidazolate frameworks (ZIFs), a subclass of metal–organic frameworks (MOFs), are particularly attractive carriers due to their structural tunability and chemical stability. While ZIF-8 has been extensively studied, its denser and thermodynamically more stable analog ZIF-zni has received far less attention. In this work, we report the biomineralization of glucose oxidase (GOx) from Aspergillus niger within the ZIF-zni framework and systematically investigate the influence of zinc and imidazole (Im) concentration on immobilization performance. The optimized biocomposite, obtained at 10 mM Zn²⁺ and a Zn:Im ratio of 1:10, exhibited a specific activity of 2051 IU g⁻¹, which is more than twice the activity obtained for GOx@ZIF-8 in our previous study (874 IU g⁻¹). Furthermore, the GOx@ZIF-zni biocomposite demonstrated remarkable resistance to sodium dodecyl sulfate (SDS) and retained up to 50% of its activity after incubation at 65 °C for one hour. These results demonstrate that ZIF-zni is a highly promising carrier for enzyme immobilization and suggest that framework topology and synthesis conditions play a crucial role in determining the catalytic performance and stability of enzyme@MOF biocomposites. Full article

Zeolitic imidazolate framework-8 (ZIF-8) is one of the most extensively studied metal–organic frameworks due to its high surface area, tunable porosity, chemical stability, and intrinsic antimicrobial activity. Recent research has focused on engineering ZIF-8 through metal doping and surface functionalization to enhance its physicochemical performance and expand its applications in food safety and environmental systems. Metal-doped ZIF-8 incorporating Cu²⁺, Fe²⁺/Fe³⁺, Ag⁺, or Mn²⁺ improves reactive oxygen species generation, enables controlled metal-ion release, and promotes synergistic bactericidal mechanisms against both Gram-positive and Gram-negative pathogens. In parallel, surface modification using biopolymers such as hyaluronic acid, chitosan, alginate, and polyethylene glycol enhances colloidal stability, reduces cytotoxicity, modulates surface charge, and improves adhesion to food-contact surfaces, thereby enhancing coating stability and sustained antimicrobial activity. These combined strategies support the development of multifunctional nanoplatforms with improved dispersibility, controlled release behavior, and compatibility with food packaging, sanitization, and water treatment applications. From a sustainability perspective, ZIF-8-based systems offer the potential to reduce reliance on conventional chemical disinfectants, minimize chemical residues, and enable the integration of biodegradable polymer matrices for safer and more environmentally responsible antimicrobial solutions. This review summarizes recent advances in synthesis strategies, structure–property relationships, antimicrobial and antibiofilm mechanisms, and environmental safety considerations. Key challenges, including scalability, regulatory acceptance, stability, and long-term ecotoxicological impact, are discussed, along with perspectives on stimuli-responsive systems, essential oil encapsulation, and smart antimicrobial coatings. Full article

Direct air capture (DAC) of CO₂ via temperature-swing adsorption (TSA) can support sustainable carbon dioxide removal, but only if sorbents regenerate with low energy demand and maintain performance under humid ambient air. In this paper, we evaluate three commercial molecular sieves (JLPM3, 13X, and 4A) in packed-bed tests using humid ambient air. We compared 40 g samples as received with 200 g samples conditioned for 12 days at 100 °C to emulate prolonged exposure to regeneration temperature (the cumulative effect of many heating/desorption cycles); all cycle-stabilized uptake values are reported from the conditioned materials. JLPM3 delivered the highest stabilized CO₂ uptake (0.24 ± 0.01 mmol·g⁻¹), consistent with a combined physisorption/chemisorption mechanism. Its higher total porosity (26.190%) and smaller mesopores (7.569 nm width) promoted rapid mass transfer and site accessibility, while slightly greater micropore area (710.285 m²·g⁻¹) and volume (0.267 cm³·g⁻¹) than 13X supported its marginally higher capacity. Evidence of partial structural degradation under mechanical and thermal stress indicates that minimizing strain during cycling will be important for scale-up and for reducing sorbent replacement. Conditioning at 100 °C activated additional chemisorption sites across all sieves but reduced physisorption capacity. Importantly, a ~100 °C desorption step fully regenerated physisorbed CO₂ while purging moisture from zeolite pores, indicating that low-temperature TSA (compatible with low-grade or waste heat) can replace harsher 300 °C regeneration and lower energy demand. CO₂–H₂O competition experiments confirmed substantial site occupancy by water vapor, which limits capture under humid conditions and motivates water management strategies. Overall, maximizing DAC performance requires tailoring pore structure and operating conditions while preserving sorbent integrity; JLPM3 emerges as a promising candidate for more energy- and resource-efficient DAC. Full article

This study evaluates the performance of Ni-La₂O₃/Beta catalysts for the dry reforming of methane, focusing on the effects of nickel loading, catalyst pretreatment, reaction temperature, and gas composition and flow rate. Catalysts with nickel contents ranging from 3 to 20 percent by weight were prepared via wet impregnation and characterized by gas adsorption, X-ray diffraction, temperature-programmed reduction with hydrogen, thermogravimetric analysis, and transmission electron microscopy. The results indicate that nickel gradually incorporates into the zeolitic support, preferentially occupying the most stable sites. Direct reduction of the impregnated catalyst precursors—omitting the calcination step—yielded materials with slightly higher methane conversion (ca. 3.5%) and enhanced stability. This improved performance is attributed to the reduction occurring during the thermal decomposition of supported nickel nitrate, which promotes finer nickel dispersion and stronger interaction with the La₂O₃-modified Beta zeolite. Full article

This study addresses the challenge of separating powdered zeolite adsorbents by developing biomass-supported composites via in situ crystallization of zeolites NaA (LTA) and NaX (FAU) within lead tree wood. Wood was mixed with precursor gels and subjected to hydrothermal treatment, yielding composites and external zeolite powders. Phase formation and morphology were confirmed by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The zeolite content in the composites was estimated from TGA to be approximately 10 wt.% for LTW–NaA and ~2 wt.% for LTW–NaX. Cu(II) adsorption was evaluated under controlled conditions and analyzed using Langmuir and Freundlich models together with Giles classification. The NaA powder showed the highest capacity (q_m ≈ 210 mg g⁻¹), while composite performance reflected zeolite loading. When normalized by zeolite mass, the composites exhibited comparable or enhanced capacities relative to powders, suggesting improved accessibility of active sites. NaA-based materials displayed H-type isotherms, whereas NaX-based materials showed L-type behavior, indicating different adsorption mechanisms. These results demonstrate that framework topology and biomass confinement jointly influence adsorption and that the composites are promising, easily recoverable adsorbents, with further work required to assess regeneration and long-term stability. Full article

Ethylene–propylene–diene monomer rubber (EPDM) is commonly used as a gas-tight sealing material in electrical equipment. Factors such as media exposure, thermal oxidative stress, and abrasion frequently cause deterioration of EPDM’s mechanical properties, significantly compromising the reliability of electrical equipment. Traditional activator ZnO provides limited enhancement to the properties of EPDM. The reaction between Zn²⁺ on the surface of zinc oxide interacts with the accelerator during curing of rubber, forming zinc chelates, which interact with sulfur to form zinc polysulfide complexes. But the release of zinc complexes has adverse effects on humans and ecosystems. To reduce ZnO usage and further improve the performance of EPDM in terms of mechanical properties and aging resistance, zeolitic imidazolate framework-8 (ZIF-8) is developed as a multifunctional additive in this work. Mechanical testing demonstrates that the incorporation of ZIF-8 enhances the mechanical performance and resistance to thermal oxidative aging of EPDM. Crosslink density testing, FTIR, and XPS show that ZIF-8 promotes the crosslinking reaction during rubber curing, resulting in improved mechanical performance for EPDM. Analysis of crosslinking density testing and SEM images shows that EPDM-ZIF-8 composite exhibits a slower increase in crosslinking density during thermal oxidative aging. TGA results indicate that ZIF-8 enhances the thermal stability of EPDM, which leads to improved aging resistance properties. This study provides new insights for the design and development of rubber composite materials, offering a reliable solution to the challenge of seal failure in electrical equipment. Full article

The rising demand for clean water has reinforced the importance of thin-film composite TFC polyamide membranes in desalination and wastewater treatment. While improvements often target the selective layer, these can sometimes reduce stability or selectivity. An alternative approach is to tailor the porous support, particularly through the incorporation of nanomaterials such as metal oxides, carbon-based nanomaterials, metal–organic frameworks (MOFs), zeolites, and cellulose-based materials, to improve overall membrane performance. The modification of membrane substrates through the incorporation of nanofillers has demonstrated notable advantages, including enhanced hydrophilicity, improved mechanical stability, and increased porosity. These improvements collectively contribute to higher permeability, reduced internal concentration polarization and enhanced separation performance in FO, NF, and RO applications. The review starts by clearly distinguishing substrate modification, in which nanomaterials are localized in the porous support, from interlayer modification, which involves constructing a distinct layer between the support and selective layer. This concise review highlights current developments in the nanomaterial-based support modification of polyamide TFC membranes; it summarizes nanomaterials selections, incorporation techniques, and resulting property changes. Current challenges and potential research opportunities are also discussed. Full article

The oxygen evolution reaction (OER), a key half-reaction in electrochemical water splitting, is limited by sluggish multi-electron transfer kinetics, starting extensive research into efficient, low-cost nanoscale electrocatalysts, particularly those based on nickel, cobalt, and iron, as well as mixed-metal, hybrid, and heteroatom-doped carbon-based metal-free systems, as presented here. Ni- and Co-based electrocatalysts show high efficiency for alkaline OER due to optimized nanostructures, surface modifications, heterostructure design, and multi-metal doping, which enhance activity, stability, and electronic properties. Their performance relies on precise atomic-level control of structure and synergistic interactions, enabling them to approach or rival noble-metal catalysts. Iron-based electrocatalysts are also promising due to their abundance, low cost, and flexible redox chemistry, forming active iron oxyhydroxide species during operation; however, their low conductivity requires structural and electronic optimization. Beyond Fe, Ni, and Co, copper-based compounds, zeolitic imidazolate framework-derived structures, and manganese phosphide–cerium oxide composites offer enhanced oxygen vacancies, tunable structures, and strong interfacial synergy. Furthermore, heteroatom-doped carbon materials incorporating nitrogen, phosphorus, or sulfur improve catalytic activity by modifying electronic structure, creating active sites, and enhancing charge transfer. Overall, careful control of composition, structure, and electronic properties enables the development of efficient, durable, and scalable noble-metal-free catalysts for OER. Full article

The critical role of lithium in powering the new energy economy necessitates prioritizing efficient extraction methods. This study investigates a novel zeolitic imidazolate frame work (ZIF-8)-coated manganese-based lithium-ion sieve (LIS) for enhanced lithium recovery. The precursor of LIS, Li_1.6Mn_1.6O_4, was synthesized via the hydrothermal method, followed by acid pickling to obtain the spinel lithium-ion sieve H_1.6Mn_1.6O₄. The material was then immersed in a 2-methylimidazole/Zn(NO₃)₂ solution, undergoing ultrasonic-assisted hydrothermal growth to form H_1.6Mn_1.6O₄@ZIF-8 composites. Under optimized conditions (30 °C, pH = 11, 24 h), the composite demonstrated superior lithium extraction performance compared to single-phase adsorbents, reaching 26.62 mg/g in the solution with 250 mg/L Li⁺. The adsorption capacity of the composite increased with Li⁺ concentration and reaction time. The adsorption kinetics followed a pseudo-second-order kinetic model and were dominated by chemisorption. The H_1.6Mn_1.6O₄@ZIF-8 composite exhibited an enhanced Li⁺ partition coefficient K_d of 118.3 in a mixed solution containing ions such as Li⁺, Mg²⁺, K⁺, and Ca²⁺, each with a concentration of 250 mg/L (pH = 12); good structural stability with manganese dissolution of 1.6%; and a capacity retention of approximately 79.5% after five cycles (C_Li⁺ = 250 mg/L). Full article

The growing volume of fiber-reinforced polymer composite waste creates an urgent need for efficient recycling technologies. While solvolysis effectively breaks down thermoset matrices for fiber reinforcement recovery, the process generates hydrocarbon-rich liquid by-products that require further management. This study validates the use of these liquid recycling streams—derived from the solvolysis of unsaturated polyester and epoxy resins—as sustainable carbon precursors for the growth of carbon nanomaterials. Synthesis was performed via catalytic chemical vapor deposition (CVD) at 850 °C using iron nanoparticles impregnated on a zeolite substrate. Morphological analysis confirmed the production of one-dimensional nanostructures (carbon nanotubes/nanofibers), with average diameters below 100 nm. Raman spectroscopy revealed a high degree of graphitization, with I_D/I_G ratios ranging from 0.25 to 0.58, which is comparable to structures synthesized from conventional precursors. Thermogravimetric analysis (TGA) demonstrated high thermal stability and carbon purity reaching up to 90.3%. These findings demonstrate a viable upcycling pathway that enhances the economic attractiveness of composite recycling by transforming waste into advanced nanomaterials. Full article

This study developed and evaluated multifunctional Cu-doped Zeolitic Imidazolate Framework-8 nanoparticles coated with hyaluronic acid (Cu-ZIF-8@HA) for antimicrobial application on stainless-steel food-contact surfaces. Structural characterization through SEM, TEM, and elemental mapping confirmed the successful synthesis, uniform Cu incorporation, and HA coating without compromising the crystalline ZIF-8 framework. Cu doping reduced particle size (~130 nm) and enhanced redox activity, while HA encapsulation improved colloidal stability and biocompatibility by shifting zeta potential from positive (+22.1 mV) to negative (−18.7 mV). Cytotoxicity assays demonstrated that HA significantly mitigated metal-induced toxicity, maintaining >70% cell viability at ≤1000 µg/mL. Antibacterial assessments revealed potent activity against Salmonella Typhimurium ATCC 14028 and Escherichia coli O157:H7, with Cu-ZIF-8@HA exhibiting the largest inhibition zones (18.15–20.33 mm), lowest MIC/MBC values (500/2000 µg/mL and 1000/2500 µg/mL), and over 6-log reductions in bacterial adhesion on stainless steel. Enhanced wettability (contact angle 11.77°) and surface energy (64.42 mN/m) further facilitated antimicrobial contact. These results confirm that Cu-ZIF-8@HA integrates the oxidative potency of Cu, the structural stability of ZIF-8, and the biocompatibility of HA, offering a promising and safe nanomaterial platform for controlling bacterial contamination and biofilm formation in food-processing environments. Full article

Methane (CH₄) is the second-largest contributor to climate change after carbon dioxide (CO₂) and has a global warming potential about 72 times greater than CO₂ over a 20-year timescale. A possible solution to mitigate CH₄ emissions from diluted sources is direct removal of CH₄ through tailored sorbents. In this work, ion-exchanged zeolites have been investigated, owing to their low cost, excellent chemical stability, and ease of production. The impact of barium, lithium, and nickel exchange was investigated, along with one, three, and five ion-exchange sequences. XRD analysis confirmed that the structure remained intact after ion exchange. However, nitrogen physisorption revealed that nickel- and barium-exchanged zeolites had reduced pore volume and surface area compared to the parent zeolite, possibly due to mesopore formation from lattice strain relaxation. ICP-OES and SEM-EDX confirmed the successful incorporation of metals into the zeolite. Finally, breakthrough experiments were carried out to assess the saturation capacity of the synthesized sample. The results demonstrated that the lithium-exchanged samples provided the highest saturation capacity, namely 1.58 ± 0.05 mmol g⁻¹ for the Li-13X-3 and 1.76 ± 0.07 mmol g⁻¹ for the Li-SAPO34-5 over 10 adsorption cycles. Furthermore, the stability of the Li-SAPO34-5 was confirmed over 100 adsorption cycles. Full article

Linear alkylbenzene (LAB) is the main raw material used to make biodegradable detergents, and its production process is based on aromatic alkylation. HY zeolites that have undergone controlled dealumination and desilication have led industrial standards amongst solid acid catalysts because of their controllable acidity and hierarchical pore structure. Coke formation in such systems can assume a dual role, which is dependent on its condition. Though the over-deposition is known to cause deactivation by blocking the micropores, Bronsted acid-site masking, and diffusion collapse, the low-level deposition could also be done to increase the monoalkylate selectivity by the pore mouth catalysis, steric modulation, and selective suppression of secondary alkylation pathways. The critical review is done on the structural-kinetic interaction that determines the coke evolution in HY-based catalysts. In order to moderate the acid-site density and enhance hydrothermal stability, dealumination (Si/Al optimization of about 2.5 to 30–100) occurs, but to reduce deep-pore coke formation, desilication (interconnected mesopores) is created. The bimodal porosity and regulated acidity are found to be synergistic, as hierarchical HY zeolites produced through successive cycles of steam and alkaline treatments not only show LAB selectivity in excess of 90% but also exhibit much longer catalyst lifetimes. Quantitative research on the beneficial coke regime revealed that it was composed of about 36 wt% hydrogen-rich species, which were localized at the pore mouths, hence enhancing monoalkylation selectivity by 15–40%. Beyond a critical transition window (e.g., 8–12 wt.%), coke formation to condensed polyaromatic and graphitic products leads to fast deactivated coke formation, which is due to percolation limits and transport-controlled kinetics. More advanced techniques of characterization of the coke, e.g., temperature-programmed oxidation (TPO), ²⁷Al MAAS NMR, and UV-Raman spectroscopy, indicate how the coke is changed to highly structured graphitic deposits of high oxidation activation energy. Activity recovery of 85–98% is obtained in regeneration processes, including controlled oxidative calcination, microwave-based and plasma-based processes, and thermal management protocols, and it would be determined by the chemistry of the coke, its spatial distribution, and the regeneration protocols. This paper has developed a mechanistic coke control system by cross-tuning the acidity and development of an effective pore network, which led to a sustainable aromatic alkylation reaction with minimal activity loss, high selectivity, and long life. Full article