Chemistry and Materials Science

Abstract: In mathematical chemistry, topological indices are frequently employed to link numerical descriptors related to chemical and biological aspects with molecular graph structures. The Sombor index is one of these indicators that has attracted a lot of interest lately because of its remarkable structural sensitivity and predictive power. In this study, we extend the conventional Sombor index to fuzzy graph situations by introducing a fuzzy graph-based Sombor index, represented by SO(Fη). Under basic graph operations, such as the union, join, composition, and Cartesian product of fuzzy graphs, several constraints for SO(Fη) are found. Additionally, a comparison analysis is carried out to examine the connection between the Sombor index and other well-known topological indices, emphasizing its usefulness in chemical graph theory. A modified fuzzy Sombor index is created and used to analyze cancer diagnosis data in China, where uncertainty in risk factors including nutrition, obesity, diabetes, and air pollution plays a critical role in disease progression, in order to show the practical applicability of the suggested index. The promise of the fuzzy Sombor index as a flexible tool connecting theoretical graph invariants and practical data analysis is demonstrated by this application.

Abstract: This work investigates the photo-Fenton degradation of azo dyes in an aqueous medium rich in sodium dodecyl sulfate (SDS), using methyl orange (MO) as a model contaminant. Chemometric modeling was integrated with mechanistic analysis to elucidate the role of the micellar pseudophase in radical distribution, dye partitioning, and overall reaction efficiency. A sequential experimental design strategy was applied, combining fractional factorial design and response surface methodology (RSM) to evaluate the individual and interactive effects of key operational variables and determine the optimal operating conditions for maximum degradation efficiency. Under optimized conditions (pH 2.85, [H₂O₂] = 100 mM, [Fe²⁺] = 0.5 mM, [SDS] = 13 mM, [MO] = 0.01 mM), MO degradation reached 98.4% in 5 minutes. Spectroscopic and partitioning studies revealed a strong affinity of MO for the micellar interface, indicating preferential localization in a microheterogeneous environment. Radical scavenging experiments confirmed that hydroxyl radicals are the dominant oxidizing species in water, while the reduction observed in the presence of SDS suggested secondary radical pathways derived from the surfactant under micellar conditions. Kinetic analyses highlighted the role of intermolecular interactions and micellar compartmentalization in radical generation. The optimized system was successfully extended to other azo dyes, underscoring the potential of surfactant-rich organized media to enhance photo-Fenton reactions in complex aqueous environments.

Abstract: Antimicrobial peptides are promising agents for combating resistant infections. They exhibit bactericidal activity against a wide range of microbes, primarily by disrupting the permeability of the bacterial membrane and ultimately causing cell death. Effective bacterial killing requires a high number of membrane-bound peptide molecules. Therefore, it is conceivable that peptide accumulation on the membrane could also interfere with essential cellular processes by altering bilayer dynamics, a hypothesis referred to as the “sand in the gearbox” model. In this work, we systematically investigated how membrane dynamics is affected by a set of well-characterized yet highly diverse peptides: the natural AMP magainin 2, the toxin melittin, the synthetic peptides LAH4 and Killer-FLIP, and small membrane-active peptidomimetics with bactericidal activity. These effects were examined using fluorescence spectroscopy techniques, by measuring anisotropy, generalized polarization, and excimer formation of specific probes inserted at different depths within the lipid bilayer. Our results show that the activity of all compounds extends beyond membrane permeabilization, and that perturbation of membrane dynamics is a common feature among all systems analyzed. The membrane-active compounds induced a stiffening of the phospholipid bilayer by reducing lipid lateral mobility and decreasing water penetration, at least on the nanosecond timescale accessible to fluorescence measurements. Interestingly, when accounting for differences in the resulting membrane surface area coverage, the concentration range in which this behavior occurred was the same for all compounds studied. This threshold is, generally, higher than that required for membrane permeabilization and reflects near-complete coverage of the bilayer surface.

Abstract: Water exhibits anomalous thermodynamic and structural behavior as it approaches and crosses below its melting point. Modelling this behaviour computationally remains challenging: as temperature decreases, nuclear quantum effects (NQE) become increasingly significant, sampling efficiency deteriorates dramatically, and the choice of computational method critically impacts the accuracy of predicted structural and dynamical properties. This review provides a comprehensive assessment of molecular dynamics methodologies for simulating water at low temperatures, with particular emphasis on the supercooled regime (200--273 K). We examine commonly used methods in ab initio molecular dynamics (AIMD) approaches, and critically evaluate strategies for incorporating nuclear quantum effects through path-integral molecular dynamics (PIMD), ring-polymer MD (RPMD), and centroid MD (CMD); below approximately 250 K the magnitude of nuclear quantum effects, and the sensitivity of structural and dynamical properties to them, grows to the point where classical treatment of the nuclei is no longer adequate. The known limitations of density functional approximations for water structure are assessed in the context of their interplay with NQE treatment, rather than in isolation. Practical considerations, including sampling efficiency and the temperature scaling of path-integral bead counts, are discussed alongside the methods.

Abstract: In this paper, we present new methods for the synthesis of picrylamino derivatives. Improvements over existing methods are demonstrated, including significantly reduced reaction times and the use of less hazardous reagents. One of these methods is recommended for the synthesis of 3-picrylamino-1H-1,2,4-triazole due to its slightly higher yield and reduced use of harmful picryl chloride. The proposed methods provide a practical approach for producing insensitive high-energy materials with good yields and high purity. The purity of the synthesized materials was confirmed by LC-MS or FT-IR spectra analysis. It is also shown that introducing substitutions into the benzene or triazole ring does not require additional synthetic steps, while the resulting compounds exhibit improved stability and/or detonation performance. The proposed methods provide a practical approach for producing insensitive high-energy materials with good yields and high purity. The stability of the picrylamino derivatives was confirmed by bullet impact tests. In addition, the structure of picrylamino-1,2,4-triazole is analyzed to provide insight into its stability. The results establish a practical and scalable approach to the development of safer, more stable, and high-performance energetic materials.

Abstract: The calculation of gas properties from the gas composition is an activity that occurs frequently in gas analysis. Such calculations play an important role in the transmission and distribution of energy gases, carbon dioxide and other commodities. They also occur in monitoring air quality. Applications include the calculation of compressibility factors of natural gas to convert metered gas volumes from actual to reference conditions, the conversion of amount fractions into mass concentrations and calculations in process design and optimisation. Evaluating measurement uncertainty is important, as usually there are legislative, regulatory and commercial requirements to be met. Assessing and demonstrating compliance with such requirements requires knowledge about the uncertainty of the measurement result. It is shown how the well-known law of propagation of uncertainty can be used with models from which it is not evident how to calculate partial derivatives, such as equations of state, which are used to calculate, e.g., compressibility factors, densities and energies. Furthermore, it is shown how to calculate time averages from measurement data in grids and networks.

Abstract: In this study, hydantoin (C₃H₄N₂O₂) was selected to investigate the photoluminescence mechanism of non-typical luminescent compounds. The emission spectra of single crystals were examined using a laser confocal microscope. Within the same crystal, the peak shape and position were consistent across different regions, while the intensity varied; this phenomenon is attributed to confinement-induced emission. For different crystal blocks, variations in molecular packing modes led to changes in both peak shape and position. Combined with theoretical calculations and analyses, the results show that: as the molecular number increases, the energy gap decreases and the excitation wavelength increases (lower excitation energy); the hole-electron attraction energy, delocalization index, and overlap degree all decrease, with the hole delocalization index decreasing faster than that of the electron; the spin-orbit coupling coefficients for high-lying triplet states are more sensitive to the molecular count; and the intersystem crossing rate increases sharply with increasing energy level. In summary, the number and mode of molecular packing in the crystal influence the excited-state electronic structure and hole-electron interactions, thereby determining the luminescence behavior of non-typical luminescent compounds.

Abstract: In protein solutions, an additive that increases protein-protein attractive interactions is expected to decrease protein crystal solubility and raise temperature of liquid-liquid phase separation (LLPS). In contrast, addition of 0.10-M 4-(2-hydroxyethyl)-1-piperazineethanesulfonate (HEPES) to lysozyme-NaCl aqueous solutions at constant pH (7.4) and ionic strength (0.20 M) decreases solubility but lowers LLPS temperature. This leads to a broadening of LLPS metastability gap in the phase diagram and an enhancement of protein crystallization yield from LLPS. We theoretically examine the effect of HEPES on both solubility and LLPS boundaries using a colloid model. Under the hypothesis that HEPES stabilizes protein-protein contacts in the crystal lattice by physical cross-linking, we apply cell theory to describe the thermodynamic behavior of the crystalline phase and use solubility data to show that HEPES increases protein-protein attraction energy by 2.7%. Since an increase in attraction incorrectly predicts a raise in LLPS temperature, we consider that HEPES also enhances the anisotropic character of protein-protein interactions. To describe the thermodynamic behavior of the solution phase, we start from Barker-Henderson second-order perturbation theory on the hard-sphere reference fluid with square-well potential and local-compressibility approximation. We modify this model so that it can reproduce the correct mathematical expression of the second virial coefficient. This also leads to a better agreement with Monte Carlo simulations. We then approximately incorporate anisotropy by assuming that the square-well attraction energy is a temperature-dependent average over all particle surface with a given fractional coverage of attractive spots. The attraction energy of the attractive spots is set to be the same as that of protein-protein contacts in the crystal. Only fractional coverage (anisotropy) was varied to successfully fit the effect of HEPES on the LLPS boundary.

Abstract: Heparin is a highly sulfated polyelectrolyte, and its properties depend a lot on its shape in solution. In this study, we closely examined the structural behaviour of UVC-irradiated low-molecular-weight heparin. By using controlled photodegradation, we created native, small, and ultra-small molar mass fractions, which allowed us to study how structural properties change with molecular weight. We examined how molar mass, radius of gyration, second virial coefficient, and critical overlap concentration are related to one another to understand different conformational states. Our results showed that as molar mass decreased, the chain diameter and persistence length also dropped, while the overlap concentration increased. This means the hydrodynamic volume went down and the chains became more flexible. The positive second virial coefficient values showed that polymer–solvent interactions remained favourable after photo-tailing. The scaling exponents suggest that degraded heparin behaves as a semi-flexible polyelectrolyte and adopts an extended-coil shape in water with electrolytes. Further analysis showed that the characteristic ratio and stiffness of the chains decreased as the chains were broken by irradiation. Overall, UVC phototailing provides a reliable way to modify the structure of these molecules while maintaining solution stability. These findings show a clear link between reduced molecular weight and changes in shape, which is useful for developing better low-molecular-weight heparins for pharmaceutical and medical use.

Abstract: Poly(l-lactic acid) or poly(l-lactide) (PLLA) is an optically active polymer derived from renewable sources and fully biodegradable. It is known that PLLA assumes a left-handed helix in the solid state and also in solution it still keeps a certain degree of helical structure. Here we examine the Optical Rotatory Dispersion (ORD) behavior of two grades of PLLA (medium molecular weight and hexadecyl-terminated or a high molecular weight for 3D printing) in 13 different solvents and through the Moffitt-Yang equation of the ORD data. Furthermore, the ORD data of PLLA in additional 6 solvents were taken from literature and analyzed with the Moffitt-Yang approach. The results suggest that also in solution PLLA maintain the left-handed helix and the most structurizing and helicogenic solvents for PLLA are ethyl acetate, acetonitrile, and certain chlorinated solvents. The equilibrium association constant (K) and other thermodynamic parameters (ΔG°, ΔH° and ΔS°) between PLLA and polyphenylacetylene (PPA another helical polymer in the solid state and in solution) were determined in trichloromethane, dichloromethane and tetrahydrofuran. The K values found suggest a strong helix-helix interaction between the two polymers. The ORD analysis of the PLLA-PPA solutions show evidences of the extrinsic Cotton effect and confirming the chiral helicity induction between the two polymers with 1:1 complex formation.

Abstract: The temporal dynamics and statistical properties of air nanobubbles (NBs) in ultrapure water were investigated using nanoparticle tracking analysis (NTA). Statistical analysis of NB lifetimes reveals a strong correlation between bubble size and persistence. The mean bubble diameter increases rapidly from ~100 nm for short-lived detections to a characteristic size of about 500 nm for bubbles surviving longer than 40 frames, after which the size remains approximately constant. The population of detected NBs decreases monotonically with increasing lifetime, approximately following an exponential decay. Spatial observations show that NBs are separated by micrometer-scale distances, excluding direct bubble–bubble interactions. Temporal analysis of the cumulative population yields a scaling exponent of ~0.6, suggesting correlated activation of localized gas micro-domains rather than independent stochastic events. These findings support a physical picture in which NBs behave as long-lived gas domains embedded in a gas–solution continuum, undergoing continuous molecular exchange with their surrounding environment. The results are consistent with non-extensive thermodynamic descriptions, where NBs are treated as diffuse interfacial entities rather than classical gas phases with sharp boundaries. Within this framework, bubble stability arises from coupling between bubble volume and local dissolved gas concentration, enabling persistence far beyond classical predictions.

Abstract: Super oxidized water is a disinfectant agent generated by electrolysis. Its effectiveness de-pends mainly on the oxidation-reduction potential and pH. In the present study, a 22 fac-torial Design of Experiments was used in order to evaluate the influence of the applied potential and the NaCl concentration on the ORP and pH of super oxidized water, with the aim of generating solutions with specific redox values for different disinfection appli-cations. The models obtained showed a high predictive capacity (R2 > 0.99), identifying NaCl concentration as the factor with the greatest effect on the oxidation-reduction poten-tial and pH. The optimized conditions presented experimental errors of less than 1.5%, thus confirming the validity of the model. The solutions showed high physicochemical stability during 24 weeks of storage. Microbiological evaluation showed antimicrobial ac-tivity against Escherichia coli, Staphylococcus aureus, Methicillin-Resistant Staphylococcus au-reus, and Candida albicans, with its responses being dependent on the ORP level and the microorganism evaluated. The results demonstrate that the use of DOE allows for the ad-justment of redox profile of super oxidized water in a controlled manner for specific ap-plications, simultaneously optimizing antimicrobial efficacy, which positions super oxi-dized water as a flexible and scalable technology for disinfection in industrial and clinical contexts.

Abstract: Waste-to-energy (WtW) systems constitute a complex thermochemical interface between energy production and waste management. This can be done by generating CO2 streams of mixed biogenic and fossil origin. Net-negative emissions can be achieved by integrating carbon capture and storage (CCS) into WtE plants. However, the physical chemistry of the capturing process under heterogeneous conditions is not yet fully understood. This review analyzes the molecular and thermodynamic foundations of CO2 capture in WtE contexts and emphasizes solvent-solute interactions, reaction equilibria, and energy landscapes governing sorption and regeneration. Moreover, the chemistry of amine-based systems, ionic liquids, and solid sorbents will be examined, with respect to flue gas composition, impurity tolerance and degradation pathways, as well as the thermodynamic and kinetic frameworks for CO2 compression, phase behavior and geochemical storage reactions. The present review presents WtE–CCS as a particular field where the principles of physical chemistry contribute substantially to the development of sustainable approaches to environmental management.

Abstract: This review examines biodegradable polymer-based core–shell nanoformulations encapsulating essential oils for acne treatment through the lens of physicochemical design and controlled delivery mechanisms. Acne is a common inflammatory skin disorder closely associated with sebum overproduction and microbial imbalance, while conventional therapies, although effective, may present long-term side effects. Increasing attention has therefore turned to sustainable dermatological materials derived from eco-friendly polymers combined with naturally active compounds. Recent advances show that core–shell nanostructures fabricated from biodegradable polymers function as physicochemically engineered carriers for volatile essential oils, enhancing their stability, protecting them from premature degradation, and enabling controlled release governed by diffusion, polymer relaxation, interfacial interactions, and degradation kinetics. The review highlights how polymer chemistry, interfacial properties, particle morphology, and processing routes determine encapsulation efficiency, release profiles, and skin permeation behavior. Particular emphasis is placed on structure–property–function relationships, including mass transport phenomena, thermodynamic compatibility between polymers and essential oils, surface charge, wettability, and nanostructure architecture, which collectively influence bioavailability and therapeutic performance. By integrating concepts from polymer physical chemistry, colloid and interface science, and drug delivery kinetics, these sustainable nanoformulations emerge as promising platforms for acne and sebum control. Overall, essential oil-loaded biodegradable polymeric core–shell systems represent a sustainable and scientifically grounded approach to acne management, although further physicochemical characterization and in vivo validation are required to support clinical translation.

Abstract: This study compares the acid dyeing of Polyamide 6 (PA6) fabric using conventional heating and microwave-assisted techniques and examines reaction parameters (temperature, time, pH, dye concentration) on conventional and microwave system. C.I. Acid Blue 324 was used to explore the effects of critical process parameters, including pH, temperature, dyeing time, and dye concentration, on color strength (K/S). Conventional and Microwave Dyeing showed an inverse correlation between pH and K/S, with optimal color yield achieved at pH 3.0. Dye uptake was enhanced by increasing temperature, with maximum K/S obtained at 95°C for 30 minutes and the highest dye concentration (1.50 %). In contrast, the microwave-assisted dyeing methodology (160 W) drastically accelerated the process. Optimal conditions for microwave dyeing also favored an acidic media (pH 3.0) and showed a strong positive correlation between microwave exposure time and K/S. The microwave-assisted technique is confirmed as a rapid, energy-efficient, green process and effective alternative for dyeing PA6, offering significant potential for reduced processing time.

Abstract: Cannabinoids are of considerable current interest for use in pharmaceutical and non-medical consumer products. While there have been significant efforts to understand their chemical stability under ambient conditions, only sparse attention has been paid to characterizing their photostability. Here, we present UVA (365 nm) and UVB (280 nm) photolysis measurements of eight representative cannabinoids, including natural compounds (THC, CBD, THCA, CBDA), metabolites (THC-COOH, THC-OH), and synthetic analogues (JWH-018, MDMB-FUBINACA). Measurements were performed using a novel online-electrospray mass spectrometry (MS) approach, where online photolysis of cannabinoid solutions was conducted with laser light emit-ting diodes. MS detection was used to monitor precursor compound decay and photoproduct formation. Complementary results obtained via UV-Vis spectroscopy of photolysed cannabinoid solutions are also presented. For THC, CBD, THC-COOH, THC-OH, THCA and CBDA significant photodegradation was observed with 280 nm photolysis, both through the appearance of photoproducts detected by MS, and via time-dependent changes in the solution UV-Vis absorption profiles. In contrast, the synthetic cannabinoids (JWH-018 and MDMB-FUBINACA) showed negligible degradation with UVB photolysis, consistent with their relatively low absorbance propensity through the mid-UV region. No significant photodegradation was observed for UVA (365 nm) photolysis of any of the cannabinoids. The results presented here constitute the first directly comparable set of photolysis measurements for key phytocannabinoids.

Abstract: Eight H-bonded complexes of arsenic acid with nitrogen bases (diethylamine, 4-methoxypyridine, pyridine-2,6-diamine, 2,4,6-trimethylpyridine, N1,N1,N2,N2-tetraethylethane-1,2-diamine, 1,3,5-triazine-2,4,6-triamine, pyridin-4-ol and 4-methoxyaniline) were studied in the solid state by single crystal X-ray diffraction technique and DFT calculations. In all cases quite short (≤ 2.65 Å) OHO bonds were found in the self-assembled supramolecular infinite chains or ribbons of dihydrogen arsenates, constituting a repertoire of five different H-bonding patterns (motifs). The electron localization function maps revealed the spots of the nucleophilic sites on oxy-gen atoms that determine the preferable directions for H-bonding of H2AsO4– anions observed in the crystal packing. Analysis of the electrostatic potential maps for isolated species has demonstrated that upon H-bonding between H2AsO4– anions and proto-nated nitrogen bases, NH+···–OAsO(OH)2, the redistribution of electron density within the anion provides otherwise virtually non-existent electrophilic sites on hydrogen atoms, which balances the Coulomb repulsion and allows for the anion···anion pairing within the crystal. The topological analysis of calculated electron density after relaxation of the hydrogen atoms’ positions was used to classify the OHO bonds as moderately strong ones (with an interaction energy up to 65 kJ/mol) and revealed a high degree of ionicity of molecular moieties within zwitterions (with an absolute charge up to 0.87 e). For the strongest OHO and NHO bonds the noticeable covalent character was shown by using the crystal orbital Hamiltonian population analysis.

Abstract:

In this study, the dyeing kinetics of polyamide fabrics with acid dyes, Telon Blue M2R, under both conventional and microwave-assisted heating conditions were comprehensively investigated. While the conventional dyeing reaction was completed in 30 minutes, microwave-assisted dyeing was performed in the microwave device for 10 minutes. Dyeing kinetics were investigated as a function of reaction time, reaction concentration and dyeing temperatures. The K/S values (color depth) of the dyed fabrics were correlated with the concentration. A significant reduction in the dyeing process time for polyamide fabric was observed with microwave heating compared to the conventional method. Kinetic analysis revealed that the PSO kinetic model provides a better fit to the experimental data on the diffusion process of acid dye in polyamide fabrics, as evidenced by higher correlation coefficients (R²) compared to the PFO model. The activation energy of the reaction in dyeing was found to be 63.27 kJ/mol, and the Arrhenius constant was determined as 7,20 x 10¹⁰ L/g.min in conventional media and 18,70 x 10¹⁰ L/g.min in microwave media. The Arrhenius factor in the microwave medium was more than two times higher than in the conventional one.

Abstract: In this work, poly(3-dodecylthiophene) (P3DDT) thin films were electrochemically synthesized using tetraethylammonium tetrafluoroborate (Et4NBF4) electrolyte. After synthesis, the films were deposited onto fluorine-doped tin oxide (FTO) substrates and subjected to optical and electrical characterizations to investigate their photophysical and electronic properties. Optical analyses were performed using ultraviolet-visible absorption spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), emission ellipsometry (EE) and Raman spectroscopy. The results revealed the formation of distinct structures during the electropolymerization process, which significantly affected the optical behavior observed in the UV-Vis and PL spectra. Furthermore, the EE measurements provided insights into the impact of these structures on the polarization states of emitted and transmitted light, on energy and charge transfer mechanisms, and on the photophysical behavior of P3DDT. Variations in the degree of polarization (P), anisotropy factor (r), and asymmetry factor (g) were analyzed as a function of the emission wavelength. The results confirm the potential of P3DDT as an active layer in electroluminescent devices, as the emissive material used in the active layer consisted exclusively of this polymer.

Abstract: The term “pristine interface” is used for differentiating emulsions that consist of only water and oil with no surfactant from the Pickering emulsions, which are also surfactant-free but stabilized with colloidal particles. We review 23 papers dedicated to such emulsions prepared from a wide variety of liquids. We studied here the evolution of one of such emulsion, hexadecane-in-water at 4% vl, over a long period of time, from days to weeks. We discovered that the droplet size is growing with time with the rate that depends on mixing conditions, which supports a coalescence hypothesis. However, this coalescence is unusual because the size reaches a certain constant value, which contradicts typical coalescence behavior. In order to explain this peculiarity, we employ a theoretical model that was developed for pristine nano-bubbles stability. We hypothesize the existence of a layer of structured water molecules at the interface, following Eastoe and Ellis (Adv in Colloid and Interface Sci., 134-135, 89-95, 2007) and many other prominent scientists. Then we point out that the Electric Double Layer exerts a force on the water dipole moments in this layer (dielectrostatic force) that compensates Kelvin’s pressure. The droplet size calculated using this model is close to the measured sizes. The second factor associated with this layer is the repulsion of the water dipole moments, which we show can compensate for surface tension parallel to the interface. After ruling out alternative hypotheses with our data, we conclude that the model suggested for explaining the stability of nano-bubbles is also consistent with our results for these “pristine emulsions”.