Search Results (228)

Ferrocenium catalysis is a growing field of research. This study investigates the catalytic activity of different ferrocenium salts in propargylic substitution reactions to afford propargylic ethers. Four different ferrocenium catalysts were employed in the title reaction, which was monitored over time. The rate of the disappearance of the starting material can be fitted to a first order rate law and observed rate constants were determined. The catalyzed propargylic substitution reactions display a moderate but discernible dependence on the ferrocenium counterion. The lack of an induction period for the reaction indicates that the ferrocenium cation itself is catalytically active, and not just a decomposition product thereof, which would result in an induction period. The presence of a carboxylic acid substituent on one of the cyclopentadienyl rings enhances catalytic activity. The Meyer–Schuster rearrangement of the propargylic alcohol to the corresponding conjugated enone played only a minor role in the ferrocenium-catalyzed reactions. Catalyst decomposition moderately retards the reaction but does not suppress product formation, as demonstrated by experiments with aged FcBF₄. In contrast, the presence of TEMPO as a radical scavenger completely inhibits product formation, while not causing detectable catalyst decomposition at room temperature. In turn, FeCl₃ catalyzes both the propargylic substitution and the Meyer–Schuster rearrangement equally and decomposes the catalysis product over time. These findings reinforce the notion that strong Lewis acids readily promote the rearrangement of propargylic alcohols and that Lewis acidity plays a crucial role in finding a balance between the substitution reactions of propargylic alcohols and their rearrangement to unsaturated aldehydes. Full article

In the realm of composite solid propellant research, the enhancement of energy performance without altering the underlying formulation holds paramount significance. This investigation employed an in situ displacement technique to establish a highly reactive interface, successfully synthesizing the [nCu+nCo+nFe]/μAl composite material, which considerably augmented the energy performance of RDX/AP. The decomposition pathways of ammonium perchlorate (AP) and RDX were optimized, resulting in a reduction in their thermal decomposition temperatures by 1.3 °C and 22.4 °C, respectively. Simultaneously, the highly reactive interface promoted efficient oxygen transport, thereby facilitating more rapid and complete reactions of aluminum. Moreover, the distinct dual-catalyst efficacy of the composite significantly enhanced the combustion efficiency of the composite energy micro-unit. Consequently, the [nCu+nCo+nFe]/μAl+RDX/AP composite energetic micro-units exhibited a notable decrease in combustion duration (from 1.58 s to 1.07 s) and elevated combustion flame temperatures (ranging from 1712.8 °C to 2205.6 °C) alongside an expanded combustion area, thus underscoring its potential for advanced propulsion applications. Full article

Modification of zeolitic structures through the incorporation of transition metal oxides has proven to be a promising approach for heterogeneous catalysis. In the present study, *BEA zeolite was modified using the incipient wetness impregnation method with varying amounts (10, 20, and 40 wt.%) of iron(III) oxide to investigate its structural and physicochemical properties. Characterization techniques such as XRD, UV–Vis DRS, FT–IR, Raman spectroscopy, SEM/EDS, TEM/EDS, and SAED, as well as textural and thermal analyses, were employed to assess the main changes. Different iron species were detected, including isolated iron(III) and well-dispersed Fe₂O₃ nanoparticles coating the zeolite surface. Under the synthesis conditions, increased Fe₂O₃ loading promoted hematite nanocrystal growth and the formation of the α-Fe₂O₃ phase, as demonstrated by XRD, Raman, and SAED analyses. Key observations included the preservation of the zeolite framework, high relative crystallinity (ranging from 70% to 85%), and a band gap of approximately 2.0 eV. Furthermore, a general increase in mesoporosity and external surface area was observed, along with a reduction in the number of acidic sites. This decrease may be attributed to restricted accessibility of the probe molecule (pyridine) to Brønsted sites due to micropore blockage in *BEA. These results demonstrate that the adopted synthesis method effectively produced α-Fe₂O₃/BEA catalysts, with no other crystalline phases of iron(III) oxide detected. Full article

The integration of polymer coatings with metal and metal oxide nanoparticles represents a significant advancement in nanotechnology, enhancing the stability, biocompatibility, and functional versatility of these materials. These enhanced properties make polymer-coated nanoparticles key components in a wide range of applications, including biomedicine, catalysis, environmental remediation, electronics, and energy storage. The unique combination of polymeric materials with metal and metal oxide cores results in hybrid structures with superior performance characteristics, making them highly desirable for various technological innovations. Polymer-coated metal and metal oxide nanoparticles can be synthesized through various methods, such as grafting to, grafting from, grafting through, in situ techniques, and layer-by-layer assembly, each offering distinct control over nanoparticle size, shape, and surface functionality. The distinctive contribution of this review lies in its systematic comparison of polymer-coating synthesis approaches for different metal and metal oxide nanoparticles, revealing how variations in polymer architecture and surface chemistry govern their stability, functionality, and application performance. The aim of this paper is to provide a comprehensive overview of the current state of research on polymer-coated nanoparticles, including metals such as gold, silver, copper, platinum, and palladium, as well as metal oxides like iron oxide, titanium dioxide, zinc oxide, and aluminum oxide. This review highlights their design strategies, synthesis methods, characterization approaches, and diverse emerging applications, including biomedicine (e.g., targeted drug delivery, gene delivery, bone tissue regeneration, imaging, antimicrobials, and therapeutic interventions), environmental remediation (e.g., antibacterials and sensors), catalysis, electronics, and energy conversion. Full article

Soil degradation and pollution pose significant threats to global agricultural sustainability and food security. Conventional remediation methods are often constrained by low efficiency, high cost, and potential secondary pollution. Nanobiotechnology, an emerging interdisciplinary field, offers innovative solutions by integrating functional nanomaterials with plant–microbe interactions to advance soil remediation and sustainable agriculture. This review systematically elaborates on the mechanisms and applications of nanomaterials in soil remediation and enhanced plant stress resilience. For contaminant removal, nanomaterials such as nano-zero-valent iron (nZVI) and carbon nanotubes effectively immobilize or degrade heavy metals and organic pollutants through adsorption, catalysis, and other reactive mechanisms. In agriculture, nanofertilizers facilitate the regulated release of nutrients, thereby markedly enhancing nutrient use efficiency. Concurrently, certain nanoparticles mitigate a range of abiotic stresses—such as drought, salinity, and heavy metal toxicity—through the regulation of phytohormone balance, augmentation of photosynthetic performance, and reinforcement of antioxidant defenses. However, concerns regarding the environmental behavior, ecotoxicity, and long-term safety of nanomaterials remain. Future research should prioritize the development of smart, responsive nanosystems, elucidate the complex interactions among nanomaterials, plants, and microbes, and establish comprehensive life-cycle assessment and standardized risk evaluation frameworks. These efforts are essential to ensuring the safe and scalable application of nanobiotechnology in environmental remediation and green agriculture. Full article

Nickel–iron (Ni-Fe) catalysts are widely used in industry due to their cost-effectiveness and versatile catalytic properties. This work investigates the structural and morphological characteristics of Ni-Fe catalysts supported on γ-Al₂O₃, synthesized with varying Ni/Fe atomic ratios (from 1:1 to 20:1). The catalysts were characterized using a combination of experimental techniques including X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), and selected-area electron diffraction (SAED). Theoretical modeling using the USPEX evolutionary algorithm complemented the experimental data by predicting stable Ni-Fe crystal structures. The results revealed uniform metal distribution on the support with particle sizes ranging from 4.1 to 4.5 nm. SAED analysis confirmed the formation of an intermetallic FeNi phase, particularly in samples with higher iron content. This study demonstrates Ni-Fe interaction effects and will be of interest to researchers in catalysis and materials science working on the development of bimetallic systems. Full article

The production of green hydrogen by microalgae is a promising strategy to convert energy of sun light into a carbon-free fuel. Many problems must be solved before large-scale industrial applications. One solution is to find a microalgal species that is easy to grow, easy to manipulate, and that can produce hydrogen open-air, thus in the presence of oxygen, for periods of time as long as possible. In this work we investigate by means of predictive computational models, the [FeFe] hydrogenase enzyme of Nannochloropsis salina, a promising microcalga already used to produce high-value products in salt water. Catalysis of water reduction to hydrogen by [FeFe] hydrogenase occurs in a peculiar iron-sulfur cluster (H-cluster) contained into a conserved H-domain, well represented by the known structure of the single-domain enzyme in Chlamydomonas reinhardtii (457 residues). By combining advanced deep-learning and molecular simulation methods we propose for N. salina a two-domain enzyme architecture hosting five iron-sulfur clusters. The enzyme organization is allowed by the protein size of 708 residues and by its sequence rich in cysteine and histidine residues mostly binding Fe atoms. The structure of an extended F-domain, containing four auxiliary iron-sulfur clusters and interacting with both the reductant ferredoxin and the H-domain, is thus predicted for the first time for microalgal [FeFe] hydrogenase. The structural study is the first step towards further studies of the microalga as a microorganism producing pure hydrogen gas. Full article

This study is focused on the hydrothermal synthesis of iron–manganese oxide nanostructures, focusing on the influence of Fe:Mn precursor ratios, temperature, and reaction time on phase formation, morphology, and structural characteristics. Three molar ratios (Fe:Mn = 2:1, 1:1, and 1:2) were explored under variable conditions (80 °C, 120 °C, and 200 °C; 4, 12, and 24 h). X-ray diffraction (XRD) analysis revealed distinct phase selectivity depending on precursor composition: FeMn₂O₄ was obtained with 1:2 ratio, Fe₃Mn₃O₈ with 1:1, and Fe₂MnO₄ with 2:1, each without phase mixing. Scanning electron microscopy (FESEM) showed a pronounced effect of temperature and time on nanoparticle morphology, ranging from compact agglomerates to well-defined rod-like structures at 200 °C/24 h. Dynamic light scattering (DLS) indicated narrow size distributions for samples synthesized at 120 °C/12 h, with hydrodynamic diameters between 20 and 50 nm. Raman spectroscopy confirmed the presence of characteristic vibrational modes of spinel-type structures and validated structural integrity. High-resolution transmission electron microscopy (HRTEM) evidenced well-ordered lattice fringes with interplanar spacings of ~0.48–0.52 nm, consistent with spinel phases and indicative of high crystallinity. These findings demonstrate that controlled atomic binding and thermal parameters enable selective synthesis of pure iron–manganese oxide phases with tailored morphologies, offering a scalable route for designing advanced functional materials in catalysis, energy, and biomedical applications. Full article

Tuberculosis, the deadliest human lung disease caused by Mycobacterium tuberculosis, continues to be a global health threat, and finding new drugs and drug targets seems an ongoing battle. The cytochrome P450 CYP125A1 enzyme of M. tuberculosis H37Rv, which is involved in cholesterol metabolism, is a well-established target for drug development. Research is ongoing to identify new compounds that target this enzyme. Understanding the structure–activity relationship of CYP125 family members is crucial for developing a specific and efficient inhibitor. In this direction, this study analyzed 21 crystal structures of CYP125 family enzymes, unraveling the factors responsible for substrate specificity and the amino acids that play a key role in catalysis. One of the unique features of CYP125A1 is its active site cavity shape, which determines the specificity of substrates and inhibitors. The active site cavity is shaped like a letter box, lined by hydrophobic residues, and it transitions into a funnel-like shape with a progressive narrowing as it approaches the heme. Due to this shape, the cholesterol and cholest-4-en-3-one serve as substrates, but not androstenedione, as the former molecules have an alkyl side chain that extends down the narrow funnel channels, interacting with the heme iron. Different binding patterns were observed for substrates and indole-derived inhibitors. Both type I and type II interactions were observed with the non-azole P450 inhibitor LP10 and indole-derived compounds, where the side chain of the indole-derived compound determined the type of interaction. This study provides a comprehensive understanding of the structure–function analysis of P450 enzymes and the interactions of CYP125A members with various ligands. Our findings pave the way for designing new and specific CYP125A1 inhibitors that will ultimately be developed into novel anti-TB drugs. Full article

In some cases, the catalytic processes involve the formation of self-organized supramolecular structures due to H-bonds and other non-covalent interactions. It has been suggested that the construction of self-assembled catalytic systems is a promising strategy to mimic enzyme catalysis at the model level. As a rule, the real catalysts are not the primary catalytic complexes, but rather, those that are formed during the catalytic process. In our earlier works, we have established that the effective catalysts M(II)_xL¹_y(L¹_ox)_z(L²)_n(H₂O)_m (M = Ni, Fe, L¹ = acac⁻, L² = activating electron-donating ligand) for the selective oxidation of ethylbenzene to α-phenyl ethyl hydroperoxide are the result of the transformation of primary (Ni(Fe)L¹)_x(L²)_y complexes during the oxidation of ethylbenzene. In addition, the mechanism of the transformation to active complexes is similar to the mechanism of action of NiFeARD (NiFe-acireductone dioxygenase). Based on kinetic and spectrophotometric data, we hypothesized that the high stability of effective catalytically active complexes may be associated with the formation of stable supramolecular structures due to intermolecular hydrogen bonds and possibly other non-covalent bonds. We confirmed this assumption using AFM. In this work, using AFM, we studied the possibility of forming supramolecular structures based on iron complexes with L²-crown ethers and quaternary ammonium salts, which are catalysts for the oxidation of ethylbenzene and are models of FeARD (Fe-acireductone dioxygenase). The formation of supramolecular structures based on complexes of natural Hemin with PhOH and L-histidine or Hemin with L-tyrosine and L-histidine, which are models of heme-dependent tyrosine hydroxylase and cytochrome P450-dependent monooxygenases (AFM method), may indicate the importance of outer-sphere regulatory interactions with the participation of Tyrosine and Histidine in the mechanism of action of these enzymes. Full article

Carbon-based nanocomposites coated with iron oxides were synthesized using a wet impregnation method with thermally annealed coal and an iron nitrate precursor. The influence of the thermal treatment atmosphere (air, vacuum, or nitrogen) on the morphology, structure, and magnetic properties of the nanocomposites was examined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. It was found that the vacuum thermal treatment produced carbon-based nanocomposite containing iron oxide with the highest crystallinity, according to XRD analysis, while also inducing the greatest degree of structural defects in the carbon matrix, as evidenced by Raman analysis. Mössbauer spectroscopy confirmed that all thermal treatment methods promote the formation of the hematite phase, which was found to be the only phase formed in the air-treated nanocomposites, whereas traces of magnetite and the formation of Fe(OH)₃ were detected in the vacuum- and nitrogen-treated nanocomposites, respectively. Magnetic characterization revealed that all nanocomposites exhibit ferromagnetic-like behavior, attributed to the weak ferromagnetic nature of hematite. The best magnetic response (highest saturation magnetization with the widest hysteresis loop) was observed in the vacuum-treated nanocomposites. These findings collectively demonstrate that the synthesis atmosphere plays a crucial role in tailoring the structural and magnetic characteristics of carbon-based iron oxide nanocomposites, offering pathways for their optimization in applications such as catalysis, environmental remediation, or sensing technologies. Full article

The efficient simultaneous removal of NO_x and CO from sintering flue gas under low-temperature conditions (110–180 °C) in iron and steel enterprises remains a significant challenge in the field of environmental catalysis. In this study, we present an innovative strategy to enhance the performance of CuSmTi catalysts through silver modification, yielding a bifunctional system capable of oxygen structure regulation and demonstrating superior activity for the combined NH₃-SCR and CO oxidation reactions under low-temperature, oxygen-rich conditions. The modified AgCuSmTi catalyst achieves complete NO conversion at 150 °C, representing a 50 °C reduction compared to the unmodified CuSmTi catalyst (T_100% = 200 °C). Moreover, the catalyst exhibits over 90% N₂ selectivity across a broad temperature range of 150–300 °C, while achieving full CO oxidation at 175 °C. A series of characterization techniques, including XRD, Raman spectroscopy, N₂ adsorption, XPS, and O₂-TPD, were employed to elucidate the Ag-Cu interaction. These modifications effectively optimize the surface physical structure, modulate the distribution of acid sites, increase the proportion of Lewis acid sites, and enhance the activity of lattice oxygen species. As a result, they effectively promote the adsorption and activation of reactants, as well as electron transfer between active species, thereby significantly enhancing the low-temperature performance of the catalyst. Furthermore, in situ DRIFTS investigations reveal the reaction mechanisms involved in NH₃-SCR and CO oxidation over the Ag-modified CuSmTi catalyst. The NH₃-SCR process predominantly follows the L-H mechanism, with partial contribution from the E-R mechanism, whereas CO oxidation proceeds via the MvK mechanism. This work demonstrates that Ag modification is an effective approach for enhancing the low-temperature performance of CuSmTi-based catalysts, offering a promising technical solution for the simultaneous control of NO_x and CO emissions in industrial flue gases. Full article

Accumulation of ferrous sulfate residue (FSR) not only occupies land but also results in environmental pollution and waste of iron resource; thus, recycling of iron from FSR has attracted widespread concern. To this end, this article shows fabrication and system analysis of hematite (HM) nanoparticles from FSR via microwave-assisted reduction technology. Physicochemical properties of HM nanoparticles were investigated by multiple analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible (UV-Vis) spectrum, vibrating sample magnetometer (VSM), and the Brunauer–Emmett–Teller (BET) method. Analytic results indicated that the special surface area, pore volume, and pore size of HM nanoparticles with the average particle size of 45 nm were evaluated to be ca. 20.999 m²/g, 0.111 cm³/g, and 0.892 nm, respectively. Magnetization curve indicated that saturation magnetization Ms for as-synthesized HM nanoparticles was calculated to be approximately 1.71 emu/g and revealed weakly ferromagnetic features at room temperature. In addition, HM nanoparticles exhibited noticeable light absorption performance for potential applications in many fields such as electronics, optics, and catalysis. Hence, synthesis of HM nanoparticles via microwave-assisted reduction technology provides an effective way for utilizing FSR and easing environmental burden. Full article

Magnetic zeolite nanocomposites (NCs) have emerged as a promising class of hybrid materials that combine the high surface area, porosity, and ion exchange capacity of zeolites with the magnetic properties of nanoparticles (NPs), particularly iron oxide-based nanomaterials. This review provides a comprehensive overview of the synthesis, characterization, and diverse applications of magnetic zeolite NCs. We begin by introducing the fundamental properties of zeolites and magnetic nanoparticles (MNPs), highlighting their synergistic integration into multifunctional composites. The structural features of various zeolite frameworks and their influence on composite performance are discussed, along with different interaction modes between MNPs and zeolite matrices. The evolution of research on magnetic zeolite NCs is traced chronologically from its early stages in the 1990s to current advancements. Synthesis methods such as co-precipitation, sol–gel, hydrothermal, microwave-assisted, and sonochemical approaches are systematically compared, emphasizing their advantages and limitations. Key characterization techniques—including X-Ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning and Transmission Electron Microscopy (SEM, TEM), Thermogravimetric Analysis (TGA), Nitrogen Adsorption/Desorption (BET analysis), Vibrating Sample Magnetometry (VSM), Zeta potential analysis, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and X-Ray Photoelectron Spectroscopy (XPS)—are described, with attention to the specific insights they provide into the physicochemical, magnetic, and structural properties of the NCs. Finally, the review explores current and potential applications of these materials in environmental and biomedical fields, focusing on adsorption, catalysis, magnetic resonance imaging (MRI), drug delivery, ion exchange, and polymer modification. This article aims to provide a foundation for future research directions and inspire innovative applications of magnetic zeolite NCs. Full article

This study presents a novel approach to fabricating magnetic sponge-like composites by melting various types of steel onto three-dimensional (3D) carbonized spongin scaffolds under extreme biomimetic conditions. Spongin, a renewable marine biopolymer with high thermal stability, was carbonized at 1200 °C to form a turbostratic graphite matrix capable of withstanding the high-temperature steel melting process (1450–1600 °C). The interaction between molten steel vapors and the carbonized scaffolds resulted in the formation of nanostructured iron oxide (primarily hematite) coatings, which impart magnetic properties to the resulting composites. Detailed characterization using SEM-EDX, HRTEM, FT-IR, and XRD confirmed the homogeneous distribution of iron oxides on and within the carbonized fibrous matrix. Electrochemical measurements further demonstrated the electrocatalytic potential of the composite, particularly the sample modified with stainless steel 316L—for the hydrogen evolution reaction (HER), offering promising perspectives for green hydrogen production. This work highlights the potential of extreme biomimetics to create functional, scalable, and sustainable materials for applications in catalysis, environmental remediation, and energy technologies. Full article