Physchem, Volume 5, Issue 2 (June 2025) – 9 articles

A comprehensive investigation of the chemical bonding, electronic structure, and spectroscopic properties of the lanarkite-type Pb₂SO₅ (PSO) structure was conducted, for the first time, using density functional theory simulations. Thus, different functionals, PBE, PBE0, PBESOL, PBESOL0, BLYP, WC1LYP, and B3LYP, were used, and their results were compared to predict their fundamental properties accurately. All DFT calculations were performed using a triple-zeta valence plus polarization basis set. Among all the DFT functionals, PBE0 showed the best agreement with the experimental and theoretical data available in the literature. Our results also reveal that the [PbO₅] clusters were formed with five Pb–O bond lengths, with values of 2.29, 2.35, 2.57, 2.60, and 2.79 Å. Meanwhile, the [SO₄] clusters exhibited uniform S–O bond lengths of 1.54 Å. Also, a complete topological analysis based on Bader’s Quantum Theory of Atoms in Molecules (QTAIM) was applied to identify atom–atom interactions in the covalent and non-covalent interactions of the PSO structure. Additionally, PSO has an indirect band gap energy of 4.83 eV and an effective mass ratio ($m_h^{*}$/$m_e^{*}$) of about 0.192 (PBE0) which may, in principle, indicate a low degree of recombination of electron–hole pairs in the lanarkite structure. This study represents the first comprehensive DFT investigation of Pb₂SO₅ reported in the literature, providing fundamental insights into its electronic and structural properties. Full article

The recovery of green waste and biomass presents a significant challenge in the 21st century. In this context, this study aims to valorize waste generated by the fruit juice processing industry at the N’Gaous unit (composed of the orange peel, fibers, pulp, and seeds) as an adsorbent to eliminate an anionic dye and to enhance its adsorption capacity through thermal activation at 200 °C and 400 °C. The aim is also to determine the parameters for the adsorption process including contact time (0–120 min), solution pH (2–10), initial dye concentration (50–700 mg/L), and adsorbent dosage (0.5–10 g/L). The adsorption tests showed that waste activated at 400 °C (AR400) demonstrated a higher efficiency for removing indigo carmine (IC) from an aqueous solution than waste activated at 200 °C (AR200) and unactivated waste (R). The experimental maximum adsorption capacities for IC were 70 mg/g for unactivated waste, 500 mg/g for waste activated at 200 °C, and 680 mg/g for waste activated at 400 °C. These tests were conducted under conditions of pH 2, an equilibrium time of 50 min, and an adsorbent concentration of 1 g/L. The analysis of the kinetic data revealed that the pseudo-second-order model provides the best fit for the experimental results, indicating that this mechanism predominates in the sorption of the pollutant onto the three adsorbents. In terms of adsorption isotherms, the Freundlich model was found to be the most appropriate for describing the adsorption of dye molecules on the R, AR200, and AR400 supports, owing to its high correlation coefficient. Before adsorption tests, the powder R, AR200 and AR400 were characterized by various analyses, including Fourier transform infrared (FTIR), pH zero charge points and laser granularity for structural evaluation. According to the results of these analyses, the specific surface area (SSA) of the prepared material increases with the increase in the activation temperature, which expresses the increase in the adsorption of material activated at 400 °C, compared with materials activated at 200 °C and the raw material. Full article

A 3-Amino-Propyl Trimethoxy Silane (APTS) functionalized silica was prepared and investigated. The functionalized silica showed a powerful removal behavior towards Chromium (III) [Cr (III)] and Cadmium (II) [Cd (II)] ions in aqueous solution. Different factors affecting the heavy metal ions adsorption on these substrates such as pH, initial concentration, contact time, and temperature were investigated. FT-IR analyses were carried out to characterize the functionalization of salicylaldehyde unto 3-aminopropyl silica. Results showed that optimum adsorption of the metal ions occurred at a pH of 7 and 6 by the pure silica and functionalized silica, respectively. Removal efficiencies of the adsorbents showed the trend: Salicylaldehyde-APTS modified > pure silica. The adsorption was described by the Langmuir adsorption isotherm. The kinetic results showed that the adsorption was described well with the pseudo second-order kinetic model. The study reveals that both pure silica and functionalized silica can be used as good adsorbents for the removal of the heavy metal pollutants from aqueous solutions and may be applied in the treatment of industrial waste waters, and they may be useful in detoxifying our already polluted environments. Full article

The aim of the study was to investigate the fixation of Cr(VI) ions from contaminated sediments using synthetic zeolite 4A and natural zeolite clinoptilolite. Parameters such as pH, contact time, adsorption mass and temperature were investigated. If the ions of the heavy metals were mobile, they would become toxic to the environment. After sediment digestion, the initial and final concentrations of Cr(VI) were measured in sediment samples with or without zeolite. Inductively coupled plasma with optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD) were used to characterize the material. The adsorption kinetics were investigated using a pseudo-first order model, a pseudo-second order model, and an intra-particle diffusion model. The results showed that the zeolites enhanced the fixation of Cr(VI). Chemisorption was the main mechanism when using acid-modified zeolite. Full article

Aluminium is an attractive material for proton-exchange-membrane fuel cell bipolar plates as it has a much lower density than steel and is easier to form than both steel and graphite. This work focused on the development of amorphous carbon films deposited using closed-field unbalanced magnetron sputtering (CFUBMS) in order to improve the corrosion resistance of aluminium bipolar plates and to enhance fuel cell performance and durability. Chromium and tungsten adhesion layers were used for the coatings. It was possible to achieve good electrical conductivity and high electrochemical corrosion resistance up to 70 °C on polished Aluminium alloy 6082 by tuning the deposition parameters. Coatings with a tungsten adhesion layer showed better corrosion resistance than those with a chromium adhesion layer. In situ, accelerated stress testing of single cells was performed using uncoated and coated Al6082 bipolar plates. Both coatings resulted in improved fuel cell performance compared to uncoated aluminium when used on the cathode side of the fuel cell. Full article

This work successfully synthesized green zinc oxide nanoparticles using extracts from strawberry guava leaves (Psidium cattleianum Sabine). Additionally, the reducing effect of the antioxidant extracts obtained through traditional techniques, such as infusion and maceration, was studied and compared against an emerging unconventional technology like ultrasound assisted extraction. Regarding the physical and chemical characteristics, it was found that all three systems were confined within a wavelength range of 357 to 370 nm (UV-vis) and sizes from 60 to 140 nm for the ultrasound-assisted nanoparticles (SEM), corroborated with DLS (134 ± 60 nm). Through X-ray diffraction, the hexagonal wurtzite structure was elucidated, and it was observed that ultrasound favored a higher percentage of crystallinity (98%) compared to the infusion (84%) and maceration (72%). This could be correlated with different functional groups via FTIR and with thermal events associated with thermogravimetric curves, where the total biomass weight loss was lower for nanoparticles using ultrasound extract (6.25%), followed by maceration (15.55%) and infusion (18.01%) extracts. Furthermore, these nanostructures were evaluated against clinically relevant pathogens, including Salmonella enteritidis, Staphylococcus aureus, Escherichia coli O157:H7, and Pseudomonas aeruginosa, assessing bacterial growth inhibition using the microdilution technique, and achieving inhibitions of 75%. Biofilm activity was evaluated through Congo red and crystal violet assays, where ultrasound-derived NPs proved to be good inhibitors for all pathogens. Finally, the toxicity of the nanoparticles was analyzed against peripheral blood leukocytes from goats as well as on the 3 T3-L1 cell line used in anti-obesity assays; the nanoparticles proved to be suitable in all concentrations reaching around 100% cell viability, positioning them as good candidates for diverse industrial applications that align with the principles of green chemistry towards a circular economy. Full article

Troponin C (TnC) is the Ca²⁺-sensing subunit of troponin that is responsible for activating thin filaments in striated muscle, and, in turn, for regulating the systolic and diastolic contractile function of cardiac muscle. The secondary structure of vertebrate TnC is mainly composed of α-helices, with nine helices named sequentially, starting from the amino terminus, from N to A–H. The N-helix is a 12-residue-long α-helix located at the extreme amino terminus of the protein and is the only helical structure that does not participate in forming Ca²⁺-binding EF-hands. Evolutionarily, the N-helix is found only in TnC from mammalian species and most other vertebrates and is not present in other Ca²⁺-binding protein members of the calmodulin (CaM) family. Furthermore, the primary sequence of the N-helix differs between the genetic isoforms of the fast skeletal TnC (sTnC) and cardiac/slow skeletal TnC (cTnC). The 3D location of the N-helix within the troponin complex is also distinct between skeletal and cardiac troponin. Physical chemistry and biophysical studies centered on the sTnC N-helix demonstrate that it is crucial to the thermal stability and Ca²⁺ sensitivity of thin filament-regulated MgATPase activity in solution and to isometric force generation in the sarcomere. Comparable studies on the cTnC N-helix have not yet been performed despite the identification of cardiomyopathy-associated genetic variants that affect the residues of cTnC’s N-helix. Here, we review the current status of the research on TnC’s N-helix and establish future directions to elucidate its functional significance. Full article

Bio-hybrid fuels, chemically derived from sustainable raw materials and green energies, offer significant potential to reduce carbon dioxide emissions in the transport sector. However, when these fuels are used as drop-in replacements in internal combustion engines, material compatibility with common sealing materials is not always given. Within the cluster of excellence, “The Fuel Science Center (FSC)” at RWTH Aachen, experimental immersion tests were conducted on a limited set of fuel and sealing material combinations. Given the extensive range of possible fuel and sealing combinations, a data-based machine learning prediction framework was developed and validated to pre-select promising fuel candidates. Due to the limited number of samples, preliminary results indicate a need to expand the database. Since experimental investigations are time-consuming and costly, this work explores faster physics-motivated data generation approaches by modeling molecular interactions between fuel and sealing materials. Two modeling scales are employed. One calculates the intermolecular distance using density functional theory. The other uses Hansen solubility parameters, representing an abstract modeling of intermolecular forces. Both approaches are compared, and their limitations are assessed. Including the generated data in the prediction framework improves its accuracy. Full article

This review focuses on the rheological behavior of polystyrene (PS) composites reinforced with carbon nanotubes (CNTs), providing an in-depth analysis of how CNT incorporation affects the viscosity, elasticity, and flow properties of these materials. The review covers fundamental aspects of PS and CNT structures, emphasizing their influence on the composite’s rheological properties. Key interaction mechanisms, including van der Waals forces and covalent bonding, are discussed for their role in determining material behavior. Various preparation methods, such as melt mixing, solution mixing, and in situ polymerization, are evaluated based on their impact on CNT dispersion and rheological performance. The study examines critical rheological parameters such as relative and complex viscosity, shear thinning, and elasticity, supported by theoretical models and experimental findings. The review also identifies major challenges, such as achieving uniform CNT dispersion and addressing processing limitations, while offering insights into future research directions aimed at improving the rheological performance and scalability of PS/CNT composites for advanced applications. Full article