Search Results (463)

We report the first examples of bent-shaped LC dimers based on a seven-membered bridged stilbene. We synthesized nonylene- and ether-linked cyano-terminated dimers (sC9-tCN and sOC7O-tCN, respectively) and a homologous series of nonylene-linked alkyl-terminated dimers (sC9-tCn) with alkyl carbon atoms n = 1–6. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurement were employed to investigate the phase-transition behavior and LC phase structures. sC9-tCN and sOC7O-tCN only exhibited a nematic (N) phase, whereas sC9-tCn (n = 1–5) formed both the N_TB and N phases. sC9-tC5 additionally formed an unidentified X phase from the N_TB phase and sC9-tC6 exhibited a smectic A phase from the N phase. The weak dispersion force and intermolecular affinity provided by the terminal alkyl chains are likely to be preferable to the large dipole–dipole interactions by the cyano termini for the N_TB phase formation of the present dimers. The isotropic points of sC9-tCn showed an odd–even oscillation with n, whereas the N–N_TB phase transition temperatures were comparable. Remarkably, the N_TB stripe textures of sC9-tCn appeared perpendicular to the rubbing direction, and the N–N_TB phase transitions exhibited their second-order nature. This study revealed the unique N_TB phase properties of the 7-membered bridged stilbene-based LC dimers. Full article

The Lewis acid (LA)-promoted formal [3 + 2] cycloaddition (32CA) reaction of 2-phenyl-1-tosylaziridine (2PTA) with ketone has been studied within the framework of Molecular Electron Density Theory (MEDT) at the ωB97X-D/6-311G(d,p) computational level in dichloromethane. This formal 32CA reaction proceeds through a stepwise mechanism, involving an initial BF₃ LA-promoted aziridine ring-opening process, followed by a ring-closure process to yield the 1,3-oxazolidine product. The activation enthalpy of the most favorable C2–N1 breaking bond step, ΔH^≠ = 6.42 kcal·mol⁻¹, is 20.98 kcal·mol⁻¹ lower than that of the non-catalyzed process, the aziridine ring-opening process being totally C2 regioselective and stereospecific. A topological analysis of the electron localization function (ELF) reveals that the most favorable transition state structure exhibits C2 carbocationic character; in this structure, the C2–N1 single bond has broken, while the C2–O4 single bond has not yet formed. A relative interacting atomic energy (RIAE) analysis of the aziridine ring-opening step reveals that the stabilization of the sulfonamide/LA leaving group and that of the ketone frameworks are the key factors responsible for the reduction in the activation barrier in the presence of LAs. LAs shift the mechanism of the aziridine ring-opening process from S_N2-like in the non-catalyzed reaction to S_N1-like in the LA-promoted process, which occurs with the inversion of the C2 carbon. Full article

The present study intends to evaluate the ratcheting of ER9 wheel medium carbon steel and austenitic steel samples at room and elevated temperatures subjected to uniaxial loading cycles through the use of the Ahmadzadeh–Varvani (A–V) kinematic hardening rule. The A–V framework incorporated an exponential function in the dynamic recovery term to account for the dynamic strain aging (DSA) phenomenon at temperatures where solute atoms and moving dislocations showed increased interaction. Within the DSA domain at 573K for ER9 wheel steel samples, and at 423K for austenitic steel samples, the collision of carbon and nitrogen solute atoms with moving dislocations resulted in the materials hardening, and promoted the yield strength. The Voyiadjis–Song–Rusinek (VSR) multivariable model was used to capture the evolution of yield strength with temperature. The predicted ratcheting results within the DSA temperature domain were in close agreement with those of measured values. Full article

This study utilizes QM/MM Born–Oppenheimer Molecular Dynamics in order to model the process of intermolecular binding between reduced graphene oxide (rGO) and butadiene–acrylonitrile copolymer (PBDAN) with a monomer ratio of 2:1. This research aims to elucidate the structural reasons behind the enhancing properties of the substrate, focusing on the polymer matrix. The behavior of each phase was examined and discussed. More importantly, the intermolecular interactions within the interphase zone of adsorption were investigated on an atomic scale. We found and characterized 58 such instances, grouped into hydrogen bonds and three types of stacking: π–π, σ–π, and σ–n. Each occurrence was analyzed through the use of radial distribution functions. Five spontaneous chemical processes within the rGO nanoparticle were modeled and characterized. Two of them were found to provide stabilization only within the substrate, while the rest are relevant for the overall constitution of the heteromaterial. Perhaps most intriguing is the process of self-repair as part of the vacancy defect. This occurs entirely within the carbon frame of the rGO layer. We believe our results to be of importance for a large set of ligand materials, mostly those which contain unsaturated bonds and electronegative atoms. Full article

Electrochemical CO₂ reduction (CO₂RR) is a promising route to transform a major greenhouse gas into value-added fuels and chemicals. However, its deployment is still hindered by the sluggish activation of CO₂, poor selectivity toward multielectron products, and competition with the hydrogen evolution reaction (HER). Single-atom catalysts (SACs) have emerged as powerful materials to address these challenges because they combine maximal metal utilization with well-defined coordination environments whose electronic structure can be precisely tuned through metal–support interactions. This minireview summarizes current understanding of how structural, electronic, and chemical features of SAC supports (e.g., porosity, heteroatom doping, vacancies, and surface functionalization) govern the adsorption and conversion of key CO₂RR intermediates and thus control product distributions from CO to CH₄, CH₃OH and C₂⁺ species. Particular emphasis is placed on selectivity descriptors (e.g., coordination number, d-band position, binding energies of *COOH and *OCHO) and on rational design strategies that exploit curvature, microenvironment engineering, and electronic metal–support interactions to direct the reaction along desired pathways. Representative SAC systems based primarily on N-doped carbons, complemented by selected examples on oxides and MXenes are discussed in terms of Faradaic efficiency (FE), current density and operational stability under practically relevant conditions. Finally, the review highlights remaining bottlenecks and outlines future directions, including operando spectroscopy and data-driven analysis of dynamic single-site ensembles, machine-learning-assisted DFT screening, scalable mechanochemical synthesis, and integration of SACs into industrially viable electrolyzers for carbon-neutral chemical production. Full article

Hydrogen storage technologies are improving over time, such as in the case of hydrogen adsorption in systems, which has been investigated in various experimental ways, as well as with theoretical methods. The design of systems that meet the needs of their experimental application is one of the challenges of these days. There are different strategies to generate adsorption of more hydrogen molecules, and several research groups have chosen to use alkali metal atoms to cause better interactions between surfaces and hydrogen molecules. Carbon, silicon, boron, phosphorus, and other systems have been reported, with carbon nanostructures being the most widely used. This review describes theoretical studies based on the addition of lithium atoms to various materials to increase the adsorption properties of hydrogen molecules. Full article

Interactions between alkaline solutions and the surface of pyrolytically coated graphite tubes (PCGTs) with/without a platform for determination of vanadium using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) are discussed. Changes on the surface of tubes, lifetime of tubes, and formation of memory effect in the determination of vanadium in alkaline solutions (NaOH, Na₂CO₃, and real alkaline slag leachates) were investigated. Based on the results obtained, it is possible to state that HR CS GFAAS determination of vanadium content in alkaline solutions reveals that PCGTs with a platform are more susceptible than those without a platform to the formation of deposits and degradation of the platform surface, especially after the application of hydroxide environments. More marked and faster formation of deposits leads to shortening of the analytical lifetime of PCGTs with a platform (approx. 70 atomization/analytical cycles (ACs)) compared to PCGTs without a platform (approx. 290 ACs). The mechanical life of both types of tubes is comparable (approx. 500 ACs). Deposits formed on the internal surface of PCGTs can be removed in the presence of a carbonate environment and higher temperatures. Damage to the PCGT surface leads to the formation of scaled shapes and cavities, which can result in decreased absorbance due to losses of vanadium in the cavities (negative measurement error), or in increased absorbance by washing out of vanadium from the cavities (positive measurement error, and formation of memory effect). It was found that more frequent cleaning of PCGTs by performing ACs in an environment of 4 mol L⁻¹ HNO₃ can eliminate these unfavourable phenomena. Our results have shown that in the case of samples analysed with different sample environments (acidic vs. alkaline), the surface material of the tube/platform wears out more quickly, and therefore it is necessary to include a cleaning stage after changing the nature of the environment. Full article

This study presents a systematic approach for converting low-grade carbon derived from mining waste into functional carbon–zeolite composites with enhanced adsorption performance. To promote carbon deposition within and around zeolite frameworks, four industrially relevant zeolites, including zeolite socony mobil-5 (ZSM-5), Faujasite-type zeolite (Zeolite-Y), beta zeolite (Zeolite-β), and mordenite (MOR), were mechanically mixed with low-grade carbon under controlled stirring conditions (24 h at 250 rpm) and subsequently pyrolyzed at 800 °C. These treatments enabled a detailed assessment of structural stability and carbon–zeolite interactions. Scanning electron microscopy revealed pronounced modifications in surface morphology and carbon distribution after carbon treatment, while X-ray diffraction confirmed that the crystalline zeolite frameworks remained structurally intact despite the deposition of amorphous carbon. The adsorption performance of the resulting composites was evaluated through CO₂ adsorption measurements under controlled temperature and pressure conditions, demonstrating a clear enhancement relative to the pristine zeolites. Overall, this work highlights an effective strategy for valorizing low-grade carbon waste into high-performance carbon–zeolite hybrid adsorbents and provides new mechanistic insights into framework stability, selective atom removal, and carbon–zeolite interactions in high-temperature and acidic environments. Full article

The structure of self-assembled monolayers (SAMs) greatly influences electrochemical interface behavior. This study systematically examines how positional isomers of aromatic diamines (ADMs) assemble on a glassy carbon (GC) electrode and how such ordering affects the attachment and performance of electrochemically reduced graphene oxide (ERGO). SAMs of ortho-, meta-, and para-phenylenediamine (o-PDA, m-PDA, and p-PDA) were fabricated on GC and characterized using atomic force microscopy (AFM) and Raman spectroscopy. Among them, GC/p-PDA exhibited the most compact and homogeneous interfacial structure. ERGO was subsequently immobilized through the free amine functionalities of the SAM, as confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Strong covalent coupling and electrostatic interactions between the positively charged ERGO and terminal amines enabled stable attachment. Under optimized conditions, the modified GC/p-PDA/ERGO electrode demonstrated exceptional electrocatalytic activity toward nitrobenzene (NBz) reduction, achieving a high sensitivity of 1410 μA mM⁻¹ cm⁻² and a low detection limit of 0.040 μM. In addition, this sensor displayed outstanding anti-interference capability, stability, and recovery in a water sample. These results establish GC/p-PDA/ERGO sensor as a robust and efficient electrocatalytically active interface for nitroaromatic pollutants detection and sustainable environmental monitoring. Full article

Fulgides are a class of organic compounds that exhibit photochromic behavior in both the solid state and in solution. These compounds have attracted considerable research interest due to their wide range of potential applications, including photochromic eyewear, smart windows, optical switches, data storage, and chemical and biological sensors. Here, we report the synthesis and crystal structures of fulgides bearing four different para-substituents on the phenyl moiety. All four molecules crystallize in space groups containing an inversion center. The distances between the two carbon atoms that would form the single C–C bond in the cyclized products fall within the range of 3.301–3.475 Å. The observed structural variations are attributed to intermolecular interactions based on Hirshfeld surface analysis. The fulgides exhibit photochromism, but they are not expected to display ferroelectric behavior due to their crystallization in centrosymmetric space groups. Full article

The development of membranes and patches for controlled drug release to enhance therapeutic efficacy is a promising approach to addressing the challenge posed by poor adherence to pharmacological therapies for chronic diseases. In this study, we designed an electrospun polycaprolactone (PCL) nanofibrous membrane reinforced with different concentrations (0.04%, 0.05%, 0.075%, and 0.2%) of functionalized multi-walled carbon nanotubes (f-MWCNTs) intended for biomedical applications, such as transdermal devices. We characterized the resulting composites using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and dynamic mechanical analysis (DMA) to evaluate their morphology, chemical composition, and mechanical properties. We also measured their cytotoxicity upon contact with peripheral blood mononuclear cells. The nanofibers had diameters below 100 nm and inclusions of microspheres, which were attributed to the electrospinning expansion phenomenon. Spectroscopic and mechanical analyses confirmed molecular interactions between the PCL matrix and the f-MWCNTs. Finally, biological tests demonstrated that both the dispersion of f-MWCNTs and the nanofiber sizing render the membranes biocompatible, supporting their potential use as drug-delivery systems. Full article

The growing pressure to achieve carbon neutrality has exposed major limitations in current industrial processes, which often operate in isolation, rely on simplified mass-balance assumptions, and struggle to manage increasingly complex material and energy flows. Traditional industrial symbiosis and circular economy strategies have improved resource efficiency, yet they rarely capture molecular-level interactions or enable coordinated optimization across multiple facilities, restricting their ability to support large-scale decarbonization. In this context, Carbon–Hydrogen–Oxygen Symbiosis Networks (CHOSYNs) have emerged as an advanced framework that integrates atomic-level targeting with multi-scale process systems engineering to identify synergies, valorization pathways, and cross-sector exchanges that conventional approaches overlook. This review consolidates the theoretical foundations, historical development, and recent applications of CHOSYNs, illustrating how it can enhance efficiency, reduce emissions, and strengthen resilience in energy systems, chemical industries, and circular resource management. Although the literature remains limited, existing studies demonstrate the promise of CHOSYNs as a unifying methodology for designing low-carbon industrial ecosystems. Key challenges related to scalability, validation, governance, and operational robustness are examined, and a roadmap is proposed to guide the evolution and practical deployment of CHOSYNs toward 2035. Full article

A detailed investigation of the structure–property relationships of three-antennary oligoglycines in aqueous solutions is performed. Two representatives of these substances are investigated: CH₃C(-CH₂-NH-Gly₅)₃ and CH₃C(-CH₂-NH-Gly₇)₃. The aim is to clarify the effect of molecular peculiarities and the concentration of the oligoglycines on bulk-solution performance and on adsorption-layer properties at the solution–air interface. This study is focused on the clarification of the conditions for the onset of bulk and interfacial supramolecular species in the aqueous environment. The presence of oligoglycine antennae attached to a common carbon-atom center allows the formation of highly coordinated intra- and intermolecular ‘click-clack’ interactions and presumes the possibility for the development of extended H-bonded networks, e.g., in the form of Polyglycine II motifs. A combined study protocol, including dynamic light scattering, profile analysis tensiometry, and microscopic thin-liquid-film techniques, is applied. The results allow the drawing of essential conclusions about the possible coupling mechanism of bulk and interfacial phenomena. The outcomes give grounds to advance the following hypothesis: due to the synchronized action of noncovalent interactions, three types of tectomeric structures may appear—dimers, gel-like elements, and disk-like supramolecular entities. Options for fine-tuning of the tectomer formation in aqueous solutions are presented, and possible application routes are outlined. Full article

Graphitic nanomaterials have emerged as foundational components in nanoscience owing to their exceptional electrical, mechanical, and chemical properties, which can be tuned by controlling dimensionality and structural order. From zero-dimensional (0D) quantum dots, carbon nano-onions, and nanodiamonds to one-dimensional (1D) nanoribbons, two-dimensional (2D) nanowalls, and three-dimensional (3D) graphene foams, these architectures underpin advancements in catalysis, energy storage, sensing, and electronic technologies. Among various synthesis routes, chemical vapor deposition (CVD) provides unmatched versatility, enabling atomic-level control over carbon supply, substrate interactions, and plasma activation to produce well defined graphitic structures directly on functional supports. This review presents a comprehensive, dimension-resolved overview of CVD-derived graphitic nanomaterials, examining how process parameters such as precursor chemistry, temperature, hydrogen etching, and template design govern nucleation, crystallinity, and morphological evolution across 0D to 3D hierarchies. Comparative analyses of Raman, XPS, and XRD data are integrated to relate structural features with growth mechanisms and functional performance. By connecting mechanistic principles across dimensional scales, this review establishes a unified framework for understanding and optimizing CVD synthesis of graphitic nanostructures. It concludes by outlining a path forward for improving how CVD-grown carbon nanomaterials are made, monitored, and integrated into real devices so these can move from lab-scale experiments to practical, scalable technologies. Full article

Defect engineering can effectively regulate the catalytic activity of single-atom catalysts anchored on the graphene substrate. Based on graphene with topological defects consisting of 5,7-membered carbon rings, we designed and investigated twenty transition metal single-atom catalysts TM-N₄-C57 (TM = Sc~Cu, Zr~Mo, Ru, Rh, Hf~Ir) for electrocatalytic nitrogen reduction reaction (NRR) using density functional theory (DFT) calculations. Employing a screening strategy that considers binding energy, N₂ adsorption, catalytic activity, selectivity, and thermal stability, we ultimately screened out two electrocatalysts (Mo-N₄-C57 and W-N₄-C57) with excellent catalytic activity and selectivity. The NRR pathways on these two catalysts proceed through distal and consecutive pathways, with limiting potentials of −0.19 and −0.53 V for Mo-N₄-C57 and W-N₄-C57, respectively. The activity origin was elucidated through the analysis of partial density of states (PDOS) and crystal orbital Hamilton populations (COHP), suggesting that the interaction between Mo and NH₂ in the *NH₂ intermediate is relatively weak. An excellent linear relationship between U_L and ICOHP has been identified, suggesting it as a descriptor. This work provides a theoretical basis for designing efficient NRR catalysts with modified second coordination spheres. Full article