Ramonna I. Kosheleva

A novel method for quantifying tortuosity by analyzing the pressure distribution of gas within a rotating porous bed is presented. The method utilizes a custom-designed disc-shaped cell packed with activated carbon particles and subjected to a high-speed rotation of 5000 rpm under an equilibrium initial pressure of 5045 mbar CO₂. The theory related to this method is outlined. From the radial pressure distribution, the apparent tortuosity is estimated to be ~2.3. This value is independently validated using an extracted apparent diffusion coefficient of D_app = (9.7 ± 0.3) × 10⁻⁷ m²/s and a corresponding tortuosity of τ_app = 2.2 ± 0.8. The findings establish a new route for probing the interplay between pore geometry, gas transport, and adsorption phenomena under centrifugal forces.

In situ and operando small-angle X-ray and neutron scattering (SAXS and SANS) have become powerful techniques for studying adsorption processes because they provide real-time information that traditional ex situ methods cannot capture. This review examines the use of these techniques in four major material groups: soft matter and polymers, carbon-based materials, biological systems and ceramics. Unlike conventional before-and-after characterization, in situ methods allow researchers to follow structural changes during adsorption as they happen, revealing adsorption kinetics, intermediate states and pore-filling mechanisms. Operando approaches further connect nanoscale structural evolution with overall adsorption performance, leading to deeper mechanistic understanding. Important developments include monitoring structural rearrangements in polymers during adsorption, studying sodium storage mechanisms in hard carbon anodes using combined small- and wide-angle neutron scattering, observing protein conformational changes at hydrated interfaces, and identifying organic functional groups in mesoporous ceramics in real time. SANS contrast variation, especially through hydrogen/deuterium substitution, allows selective visualization of different components in complex systems, while synchrotron SAXS enables kinetic studies with millisecond time resolution. Despite these advantages, several challenges remain, including model-dependent interpretation of scattering data, difficulties in separating real structural changes from contrast-related artifacts, limitations in accessible timescales and the technical complexity of isotopic labeling. Future research is expected to focus on improved contrast methods, machine learning-assisted data analysis, multimodal approaches combining scattering with spectroscopy or microscopy and the application of these techniques to more complex and disordered adsorbents such as activated carbons, coals and bio-based materials. Overall, this review summarizes current methodologies, compares adsorption-related structural changes across different materials and highlights both current limitations and future opportunities for in situ and operando SAS studies in adsorption research.

The effect of high-gravity fields, generated by rapid rotation, on CO₂ adsorption in activated carbon beds is examined. Adsorption-desorption kinetics is monitored before, during, and after short rotation periods at up to 5000 rpm. Rotation induced a reproducible transient bump in headspace pressure, quantitatively attributed to a centrifugal free energy shift (~12.2 J/mol) that overfilled weak adsorption sites beyond their static equilibrium. The bump mechanism is described by fold catastrophe theory, with a critical angular velocity (ω_c = 3500 rpm) triggering a sudden transition to a high-occupancy branch. Post-rotation, constant-rate zero-order desorption from shallow sites overlapped with a slower pseudo-first-order adsorption process as deep, previously inaccessible pores became available, increasing CO₂ capacity by 2.5%. Kinetic modeling produced an apparent diffusivity of 1.2 × 10⁻⁵ m²/s and a structural accessibility time constant of ~25 h. Thermodynamic analysis showed that rotation improved the overall free energy of adsorption and altered entropy in a manner consistent with the observed adsorption-desorption sequence. These results demonstrate that rotational fields can enhance CO₂ uptake, modify kinetic pathways, and trigger threshold phenomena in porous adsorbents.

Two hemostatic bionanocomposite dressings were developed using natural, semi-natural (or semi-synthetic) and synthetic polymers. The first system consisted of chitosan (CS), polyvinyl alcohol (PVA), and carboxymethyl cellulose (CMC) (CS/PVA/CMC), while the second was based on CS, PVA, and starch (SR) (CS/PVA/SR). Zinc oxide (ZnO) nanoparticles and bicyclic monoterpene camphor (CP) ketone were incorporated as bioactive agents in order to enhance antimicrobial and hemostatic performance. FTIR spectroscopy confirmed the successful solvent casting synthesis of the dressings and the interactions between the biopolymers and additives. XRD analysis indicated a predominantly amorphous structure, while SEM images and EDS analysis revealed uniform dispersion of ZnO particles within the polymer matrices without aggregation. Furthermore, the CS/PVA/CMC-1ZnO/CP sample exhibited a water sorption of 12,666 ± 126%, while CS/PVA/SR-1ZnO/CP reached 7013 ± 215%. ZnO incorporation also improved mechanical performance, with CS/PVA/SR-2ZnO/CP displaying the highest tensile strength (39.18 ± 0.2 MPa) and elongation at break (9.54 ± 1.04%). ZnO incorporation also led to a concentration-dependent increase in antibacterial activity, with SR-based dressings achieving near-complete bacterial reduction at higher ZnO loadings. All the dressings demonstrated good biocompatibility, while CS/PVA/SR-1ZnOCP showed the fastest clotting time (420 s ± 40), highlighting its potential for hemostatic applications.

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. Temporal analysis of the cumulative population yields a scaling exponent of ~0.6, indicating correlated fluctuations rather than independent stochastic events. Spatial observations confirm that NBs are separated by micrometer-scale distances, excluding direct bubble–bubble interactions. The combined statistical and imaging results support a picture in which NBs behave as dynamically coupled gas domains embedded within localized dissolved-gas microenvironments. The observed non-monotonic population dynamics cannot be explained by irreversible dissolution alone. Instead, the data indicate that NBs undergo continuous cycles of dissolution and replenishment. Within this framework, localized gas micro-domains, potentially exhibiting non-extensive behaviour, evolve dynamically and act as transient reservoirs. Upon bubble disappearance, these regions persist and diffuse, while their interaction may locally restore conditions for nucleation. This mechanism provides a physically consistent explanation for the observed cyclic behaviour and the apparent persistence of NBs beyond classical predictions.

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.

The effect of high-gravity fields, generated by rapid rotation, on CO₂ adsorption in activated carbon beds is examined. Adsorption-desorption kinetics is monitored before, during, and after short rotation periods at up to 5,000rpm. Rotation induced a reproducible transient bump in headspace pressure, quantitatively attributed to a centrifugal free energy shift (~12.2 J/mol) that overfilled weak adsorption sites beyond their static equilibrium. The bump mechanism is described by fold catastrophe theory, with a critical angular velocity (ωc=3,500rpm) triggering a sudden transition to a high-occupancy branch. Post-rotation, constant-rate zero-order desorption from shallow sites overlapped with a slower pseudo-first-order adsorption process as deep, previously inaccessible pores became available, increasing CO₂ capacity by 18.4%. Kinetic modelling produced an apparent diffusivity of 1.2x10-5m2/s and a structural accessibility time constant of ~25h. Thermodynamic analysis showed that rotation improved the overall free energy of adsorption and altered entropy in a manner consistent with the observed adsorption-desorption sequence. These results demonstrate that rotational fields can enhance CO₂ uptake, modify kinetic pathways, and trigger threshold phenomena in porous adsorbents.

This study investigates the development and evaluation of anti-photoaging creams enriched with natural extracts from avocado, apple, and kiwi by-products, with and without nanobubbles (NBs), focusing on their antioxidant, photoprotective, anti-inflammatory, and antiplatelet properties. Extract-containing creams showed significantly higher antioxidant capacity, particularly in the ferric reducing antioxidant power (FRAP) assay (S: 710.4 ± 344.3, NB: 566.3 ± 185.0, X: 202.8 ± 145.6 μmol TE/g DW at production; S: 631.7 ± 277.8, NB: 1019.3 ± 574.0, X: 449.8 ± 43.9 μmol TE/g DW after 1 month; p < 0.05), indicating up to a 250% improvement compared to the base cream and stable antioxidant activity during storage. The sun protection factor (SPF) increased in extract-containing creams after storage (8.7 ± 0.8 → 9.5 ± 0.6; p < 0.05). Attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) with Strat-M^® membranes revealed enhanced penetration of active compounds in enriched creams, while NBs did not significantly change absorption profiles. Platelet aggregation assays showed markedly lower half maximal inhibitory concentration (IC50) values in extract-enriched creams compared to the base cream for both the platelet-activating factor (PAF) pathway (S: 300.0 ± 42.0, NB: 258.0 ± 31.0 vs. X: 685.0 ± 35.0; after 1 month S: 325.0 ± 50.0, NB: 275.0 ± 42.0 vs. X: 885.0 ± 112.0; p < 0.05) and the adenosine diphosphate (ADP) pathway (S: 450.0 ± 65.0, NB: 400.0 ± 31.0 vs. X: 880.0 ± 58.0; after 1 month S: 470.0 ± 52.0, NB: 412.0 ± 42.0 vs. X: 1102.0 ± 125.0; p < 0.05). In silico analysis was also performed to demonstrate the ligand/protein complex with the strongest affinity to the PAF receptor. Overall, these findings highlight the potential of fruit by-products as sustainable, multifunctional cosmetic ingredients supporting circular economy principles.

Photocatalytic H₂ production is one of the most promising approaches for sustainable energy. The literature presents a plethora of carefully designed systems aimed at harnessing solar energy and converting it into chemical energy. However, the main drawback of the reported photocatalysts is their stability. Thus, the development of a cost-effective and stable photocatalyst, suitable for real-world applications remains a challenge. An ideal photocatalyst for H₂ production must possess appropriate band-edge energy positions, an effective sacrificial agent, and a suitable cocatalyst. Among the various photocatalysts studied, TiO₂ stands out due to its stability, abundance, and non-toxicity. However, its efficiency in the visible spectrum is limited by its wide bandgap. Metal doping is an effective strategy to enhance electron–hole separation and improve light absorption efficiency, thereby boosting H₂ synthesis. Common metal cocatalysts used as TiO₂ dopants include platinum (Pt), gold (Au), copper (Cu), nickel (Ni), cobalt (Co), ruthenium (Ru), iron (Fe), and silver (Ag), as well as bimetallic combinations such as Ni-Fe, Ni-Cu, Nb-Ta, and Ni-Pt. In all cases, doped TiO₂ exhibits higher H₂ production performance compared to undoped TiO₂, as metals provide additional reaction sites and enhance charge separation. The use of bimetallic dopants further optimizes the hydrogen evolution reaction. Additionally, porphyrins, with their strong visible light absorption and efficient electron transfer properties, have demonstrated potential in TiO₂ photocatalysis. Their incorporation expands the photocatalyst’s light absorption range into the visible spectrum, enhancing H₂ production efficiency. This review paper explores the principles and advancements in metal- and porphyrin-doped TiO₂ photocatalysts, highlighting their potential for sustainable hydrogen production.