Search Results (52)

This study investigated how fabrication method (milling versus 3D printing) affects the water sorption and solubility of PMMA dental materials, and how surface characteristics affect hydrolytic stability. Fifty-six PMMA samples were divided into three groups fabricated from CAD/CAM milled discs (Group A: I–III) and four groups from 3D-printed resin (Group B: IV–VII), each subjected to distinct postprocessing protocols. Water sorption (wsp) and solubility (wsl) were measured after immersion in distilled water at 37 °C for 24, 48, and 72 h, and 7 and 14 days. Surface topography and nanoroughness were assessed using atomic force microscopy (AFM). Statistical descriptive analyses were followed by correlation analyses. Milled PMMA demonstrated significantly lower water sorption and negative solubility (mass loss), indicating material dissolution. In contrast, 3D-printed PMMA showed higher water sorption and positive solubility (mass gain), reflecting water incorporation and polymer swelling. The kinetic profiles differed: milled PMMA displayed a monophasic absorption curve, while 3D-printed PMMA exhibited a biphasic pattern with accelerated water uptake after 72 h. AFM analysis revealed that 3D-printed surfaces had significantly greater nanoroughness than milled surfaces. Strong positive correlations were observed between surface roughness parameters (Sa, Sy) and water sorption capacity. The fabrication method was found to influence the hydrolytic stability of PMMA dental materials. Milled PMMA demonstrated superior stability, with lower water uptake, smoother surfaces, and lower leaching solubility. In contrast, 3D-printed PMMA exhibited increased surface roughness and water sorption, attributed to its layered microstructure and nanoporosity. Surface topography emerged as a strong predictor of wsl, related to hydrolytic degradation. For clinical applications, milled PMMA is recommended for long-term use requiring durability, whereas 3D-printed PMMA may be appropriate for short-term applications with optimised postprocessing. Full article

Alkali-activated cementitious materials are environmentally friendly alternatives to traditional cement. The structure of their core product, sodium aluminosilicate hydrate (N-A-S-H) gel, is regulated by the silicon-to-aluminum (Si/Al) ratio; however, the atomic-scale mechanism underlying this influence remains unclear. Integrating reactive force field molecular dynamics simulations and experiments, this study systematically reveals the regulation mechanism of the Si/Al ratio (1.0–2.0) on the microstructure and macroscopic properties of N-A-S-H gels. Starting from well-defined PS and PSS oligomers, the simulation results demonstrate that the Si/Al ratio governs the polymerization pathway, aluminum coordination environment (especially the content of pentacoordinate aluminum), and evolution of nanoporosity. When the Si/Al ratio is approximately 1.8, the system exhibits the highest silicate polymerization degree, lowest nanoporosity, and densest three-dimensional (3D) network structure; deviation from this ratio leads to structural degradation due to charge imbalance or excessive polymerization. These computational findings are validated by experiments on fly ash-based geopolymers: the material achieves the highest compressive strength at a Si/Al ratio of 1.8. The consistency between simulations and experiments collectively reveals a cross-scale action mechanism: the Si/Al ratio determines the macroscopic mechanical properties by regulating the nanoscale packing density and defect distribution of the gel. This study provides critical atomic-scale insights for the rational design of high-performance geopolymers. Full article

The oxygen evolution reaction (OER) plays a central role as an anode in electrocatalytic processes such as energy conversion and storage and the generation of molecular oxygen from the electrolysis of water. Currently, precious metal oxides such as IrO₂ and RuO₂ are recognized as reference OER electrocatalysts with reasonably high activity; however, their widespread use in practical devices has been severely hindered by their high cost and scarcity. It is essential to design alternative OER electrocatalysts made of low-cost and abundant earth elements with significant activity and robustness. We report four new nanocellulose-derived Fe–zeolite nanocomposites, namely Fe/Zeolite@CCNC (1), Fe/Zeolite@CCNF (2), Fe/Zeolite/CNT@CCNC (3), and Fe/Zeolite/CNT@CCNF (4). Two different types of nanocellulose were investigated: nanocellulose nanofibrils and nanocellulose nanocrystals. Characterization with TEM, SEM-EDS, PXRD, and XPS is reported. The nanocomposites exhibited electrocatalytic activity for OER that varies based on the origin of biocarbon and the composition content. The effect of adding carbon nanotubes to the nanocomposites was studied, and an improvement in OER catalysis was observed. The electrochemical double-layer capacitance and electrochemical impedance spectroscopy of the nanocomposites are reported. The nanocomposite 3 exhibited the highest performance, with an onset potential value of 1.654 V and an overpotential of 551 mV, which exceeds the activity of RuO₂ for OER catalysis at 10 mA/cm² in the glassy carbon electrode. A 24 h chronoamperometry study revealed that the catalyst is active for ~2 h under continuous operating conditions. BET surface analysis showed that the crystalline nanocellulose-derived composite exhibited 301.47 m²/g, and the fibril nanocellulose-derived composite exhibited 120.39 m²/g, indicating that the increased nanoporosity of the former contributes to the increase in OER catalysis. Full article

The development of cost-effective and scalable air/oxygen electrode materials is crucial for the advancement of Zn–air batteries (ZABs). Porous carbon materials doped with heteroatoms have attracted considerable attention in energy and environmental fields because of their tunable nanoporosity and high electrical conductivity. In this work, we report the synthesis of a three-dimensional (3D) N and P co-doped porous carbon (PA@pDC-1000), derived from a conjugated polyaniline–phytic acid polymer. The cross-linked, rigid conjugated polymeric framework plays a crucial role in maintaining the integrity of micro- and mesoporous structures and promoting graphitization during carbonization. As a result, the material exhibits a hierarchical pore structure, a high specific surface area (1045 m² g⁻¹), and a large pore volume (1.02 cm³ g⁻¹). The 3D N, P co-doped PA@pDC-1000 catalyst delivers a half-wave potential of 0.80 V (vs. RHE) and demonstrates a higher current density compared to commercial Pt/C. A primary ZAB utilizing this material achieves an open-circuit voltage of 1.51 V and a peak power density of 217 mW cm⁻². This metal-free, self-templating presents a scalable route for the generating and producing of high-performance oxygen reduction reaction catalysts for ZABs. Full article

Modern tissue engineering requires not only degradable materials promoting cell growth and differentiation, but also vascularization of the engineered tissue. Porous polylactide/polycaprolactone (PLA/PCL, ratio 3/5) foam scaffolds were prepared by a combined porogen leaching and freeze-drying technique using NaCl (crystal size 250–500 µm) and a water-soluble cellulose derivative (Klucel^TM E; 10–100% w/w relative to the total PLA/PCL concentration) as porogens. Scanning electron microscopy, micro-CT, and Brunauer–Emmett–Teller analysis showed that all scaffolds contained a trimodal range of pore sizes, i.e., macropores (average diameter 298–539 μm), micropores (100 nm to 10 μm), and nanopores (mostly around 3.0 nm). All scaffolds had an open porosity of about 90%, and the pores were interconnected. The size of the macropores and the nanoporosity were higher in the scaffolds prepared with Klucel. Nanoporosity increased water uptake by the scaffolds, while macroporosity promoted cell ingrowth, which was most evident in scaffolds prepared with 25% Klucel. Human adipose-derived stem cells co-cultured with endothelial cells formed pre-vascular structures in the scaffolds, which was further enhanced in a dynamic cell culture system. The scaffolds are promising for the engineering of pre-vascularized soft tissues (relatively pliable 10% Klucel scaffolds) and hard tissues (mechanically stronger 25% and 50% Klucel scaffolds). Full article

We compared the applicability of 3D fibrous scaffolds, produced by our patented centrifugal spinning technology, in soft tissue engineering. The scaffolds were prepared from four different biocompatible and biodegradable thermoplastics, namely, polylactide (PLA), polycaprolactone (PCL), poly(3-hydroxybutyrate) (PHB), and poly(1,4-butylene succinate) (PBS) and their blends. The combined results of SEM and BET analyses revealed an internal hierarchically organized porosity of the polymeric micro/nanofibers. Both nanoporosity and capillary effect are crucial for the water retention capacity of scaffolds designed for tissue engineering. The increased surface area provided by nanoporosity enhances water retention, while the capillary effect facilitates the movement of water and nutrients within the scaffolds. When the scaffolds were seeded with adipose-derived stem cells (ASCs), the ingrowth of these cells was the deepest in the PLA/PCL 13.5/4 (w/w) composite scaffolds. This result is consistent with the relatively large pore size in the fibrous networks, the high internal porosity, and the large specific surface area found in these scaffolds, which may therefore be best suited as a component of adipose tissue substitutes that could reduce postoperative tissue atrophy. Adipose tissue constructs produced in this way could be used in the future instead of conventional fat grafts, for example, in breast reconstruction following cancer ablation. Full article

After undergoing biological treatment, wastewater still contains substances with endotoxic activity, such as lipopolysaccharide. However, due to the increasing practice of treating wastewater to make it suitable for drinking (potable reuse), the removal of these endotoxic active materials is crucial. These substances can be harmful to human health, leading to a condition called endotoxaemia. Furthermore, environmental endotoxins pose risks to pharmaceutical manufacturing processes and the quality of the final pharmaceutical products. Ultimately, the most significant concern lies with the patient, as exposure to such substances can have adverse effects on their health and well-being. Activated carbon has a proven efficiency for endotoxin removal; rice husk (RH), as a type of natural lignocellulosic agricultural waste, is a unique carbon precursor material in terms of its availability, large-scale world production (over 140 million tons annually), and is characterized by the presence of nanoscale silica phytoliths, which serve as a template to create additional meso/macropore space within the nanoscale range. High surface area RH/lignin-derived honeycomb monoliths were prepared in this study via extrusion, followed by carbonization and physical and chemical activation to develop additional pore space. The nanoporosity of the carbon honeycomb monoliths was established by means of low-temperature nitrogen adsorption studies, using calculations based on QSDFT equilibrium and BJH models, as well as mercury intrusion porosimetry (MIP) and SEM investigations. An alternative method for the elimination of the bacterial lipopolysaccharide (LPS)—a conventional marker—using filtration in flowing recirculation systems and the adsorbent activity of the monoliths towards LPS was investigated. Since LPS expresses strong toxic effects even at very low concentrations, e.g., below 10 EU/mL, its removal even in minute amounts is essential. It was found that monoliths are able to eliminate biologically relevant LPS levels, e.g., adsorption removal within 5, 30, 60, 90, and 120 min of circulation reached the values of 49.8, 74.1, 85.4, 91.3%, and 91.6%, respectively. Full article

In recent years, the morphology control of semiconductor nanomaterials has been attracting increasing attention toward maximizing their functional properties and reaching their end use in real-world devices. However, the development of easy and cost-effective methods for preparing large-scale patterned semiconductor structures on flexible temperature-sensitive substrates remains ever in demand. In this study, vapor post-treatment (VPT) is investigated as a potential, simple and low-cost post-preparative method to morphologically modify gravure-printed zinc oxide (ZnO) nanoparticulate thin films at low temperatures. Exposing nanoparticles (NPs) to acidic vapor solution, spontaneous restructuring pathways are observed as a consequence of NPs tending to reduce their high interfacial energy. Depending on the imposed environmental conditions during the treatment (e.g., temperature, vapor composition), various ZnO thin-film morphologies are produced, from dense to porous ones, as a result of the activation and interplay of different spontaneous interface elimination mechanisms, including dissolution–precipitation, grain boundary migration and grain rotation–coalescence. The influence of VPT on structural/optical properties has been examined via XRD, UV–visible and photoluminescence measurements. Controlling NP junctions and network nanoporosity, VPT appears as promising cost-effective, low-temperature and pressureless post-preparative platform for preparing supported ZnO NP-based films with improved connectivity and mechanical stability, favoring their practical use and integration in flexible devices. Full article

Despite its potential against several carcinomas, the pharmacological efficacy of silibinin (SLB) is hampered by poor solubility, absorption, and oral bioavailability. To face these issues, we developed polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) coated with hydrophilic polyethene oxide (PEO) for controlled and targeted SLB delivery. NPs were produced at two different SLB loadings and presented a spherical shape with smooth surfaces and stable size in water and cell culture medium. The encapsulation efficiencies were found to be >84%, and thermal analysis revealed that the SLB was present in an amorphous state within the NPs. In vitro SLB release experiments revealed that at the lowest SLB loading, desorption of the active molecule from the surface or nanoporosities of the NPs mainly dictates release. In contrast, at the highest SLB loading, diffusion primarily regulates release, with negligible contributions from other mechanisms. Cell experiments showed that, compared with the free drug, SLB loaded in the produced NPs significantly increased the bioactivity against H1299, H1975, and H358 cells. Full article

Nanoporous materials, such as metal-organic frameworks (MOFs), are renowned for their high selectivity as gas adsorbents due to their specific surface area, nanoporosity, and active surface chemistry. A significant challenge for their widespread application is reduced gas uptake in wet conditions, attributed to competitive adsorption between gas and water. Recent studies of gas adsorption in wet materials have typically used small amounts of powdered porous materials (in the milligram range) within very small reactors (1–5 mL). This leaves a gap in knowledge about gas adsorption behaviors in larger reactors and with increased MOF sample sizes (to the gram scale). Additionally, there has been a notable absence of experimental research on MOFs heavily saturated with water. In this study, we aimed to fill the gaps in our understanding of gas adsorption in wet conditions by measuring CH₄ adsorption in MOFs. To do this, we used larger MOF samples (in grams) and a large-volume reactor. Our selection of commercially available MOFs, including HKUST-1, ZIF-8, MOF-303, and activated carbon, was based on their widespread application, available previous research, and differences in hydrophobicity. Using a volumetric approach, we measured high-pressure isotherms (at T = 274.15 K) to compare the moles of gas adsorbed under both dry and wet conditions across different MOFs and weights. The experimental results indicate that water decreases total CH₄ adsorption in MOFs, with a more pronounced decrease in hydrophilic MOFs compared to hydrophobic ones at lower pressures. However, hydrophilic MOFs exhibited stepped isotherms at higher pressures, suggesting water converts to hydrate, positively impacting total gas uptake. In contrast, the hydrophobic ZIF-8 did not promote hydrate formation due to particle aggregation in the presence of water, leading to a loss of surface area and surface charge. This study highlights the additional challenges associated with hydrate-MOF synergy when experiments are scaled up and larger sample sizes are used. Future studies should consider using monolith or pellet forms of MOFs to address the limitations of powdered MOFs in scale-up studies. Full article

Anodization is a method to fabricate a tunable nanoporosity and thickness of alumina coating. This research is devoted to large-area hard anodization (HA), ultrahard anodization (UHA), and transitional modes. The phenomenon and challenges of UHA and the transition from HA are studied on large-area samples using linear-sweep voltammetry. The findings indicate that a uniform large-area thick coating can be achieved by utilizing pre-UHA modes. The study’s results indicate that UHA leads only to coatings with non-uniform thickness in large-area anodization. The peculiarities of pre-UHA are studied using different temperatures (0, 5, 10, and 15 °C) and processing times (1, 2, 4, 6, and 12 h) in a 0.3 M oxalic acid electrolyte. The current study shows the possibility for the fast growth of thick nanoporous alumina up to 235 ± 4 µm for only 12 h. Full article

The automotive industry is rapidly advancing toward the electrification of vehicles. Battery electric vehicles present unique challenges in heat and noise control due to the absence of an internal combustion engine. These challenges arise from the stringent operating temperature requirements of batteries and the distinct characteristics of their power sources, such as differences in rpm and mounting positions compared to traditional engines. To address these issues, porous sound-absorbing materials and porous insulation materials are commonly employed. Conversely, there is an increasing demand for materials that are both lightweight and compact yet capable of providing excellent sound absorption and thermal insulation. Although porous sound absorbers and insulators are similar, they differ in the microstructure required to achieve high performance, specifically in the size and connectivity of their fluid phases. This increases the challenge of integrating superior sound absorption and insulation properties within the same material. In this study, computational microstructure modeling was employed to develop a non-woven fabric composed of flattened ellipsoidal particles with nanoporosity. This innovative material demonstrates exceptional thermal insulation and sound absorption characteristics attributable to its nanoporosity and high tortuosity. Full article

This work explores the effects of rigid (0.1, 0.25, and 0.5 wt. %) and semi-flexible (0.5, 1.0, and 2.5 wt. %) all-aromatic polyelectrolyte reinforcements as rheological and morphological modifiers for preparing phosphate geopolymer glass–ceramic composites. Polymer-modified aluminosilicate–phosphate geopolymer resins were prepared by high-shear mixing of a metakaolin powder with 9M phosphoric acid and two all-aromatic, sulfonated polyamides. Polymer loadings between 0.5–2.5 wt. % exhibited gel-like behavior and an increase in the modulus of the geopolymer resin as a function of polymer concentration. The incorporation of a 0.5 wt. % rigid polymer resulted in a three-fold increase in viscosity relative to the control phosphate geopolymer resin. Hardening, dehydration, and crystallization of the geopolymer resins to glass-ceramics was achieved through mold casting, curing at 80 °C for 24 h, and a final heat treatment up to 260 °C. Scanning electron microscopy revealed a decrease in microstructure porosity in the range of 0.78 μm to 0.31 μm for geopolymer plaques containing loadings of 0.5 wt. % rigid polymer. Nano-porosity values of the composites were measured between 10–40 nm using nitrogen adsorption (Brunauer–Emmett–Teller method) and transmission electron microscopy. Nanoindentation studies revealed geopolymer composites with Young’s modulus values of 15–24 GPa and hardness values of 1–2 GPa, suggesting an increase in modulus and hardness with polymer incorporation. Additional structural and chemical analyses were performed via thermal gravimetric analysis, Fourier transform infrared radiation, X-ray diffraction, and energy dispersive spectroscopy. This work provides a fundamental understanding of the processing, microstructure, and mechanical behavior of water-soluble, high-performance polyelectrolyte-reinforced geopolymer composites. Full article

In this work, hierarchically porous composites were prepared in the form of activated carbon cloth (CC) Busofit T–1–055 filled with an electrically conductive polymer, polyaniline (PANI), for use as pseudocapacitive electrodes of electrochemical supercapacitors (SCs). CC fibers have high nanoporosity and specific surface area, so it was possible to deposit (via the chemical oxidative polymerization of aniline) a significant amount of PANI on them in the form of a thin layer mainly located on the inner surface of the pores. Such morphology of the composite made allowed the combining of the high capacitive characteristics of PANI with the reversibility of electrochemical processes, high columbic efficiency and cyclic stability rather typical for carbon materials of double-layer SCs. The highest capacitance of composite electrodes of about 4.54 F/cm² with high cyclic stability (no more than 8% of capacity loss after 2000 charge–discharge cycles with a current density of 10 A/cm²) and columbic efficiency (up to 98%) was achieved in 3 M H₂SO₄ electrolyte solution when PANI was synthesized from an aniline hydrochloride solution with a concentration of 0.25 M. Trasatti analysis revealed that 27% of specific capacitance corresponded to pseudocapacitance, and 73% to the double-layer capacitance. Full article

Polymers based on 2-(acetoacetoxy)ethyl methacrylate, charged with iron or sodium, were thermally heated at 150 °C. Both polymers were studied and characterized by SEM, TEM, STEM microscopy and SAEDF techniques. The morphological investigation revealed that, upon heating, both polymers were endowed with microholes, sometimes perfectly ordered, whose dimensions varied from 4–5 nm to approximately 500 nm. In the case of an Fe-containing copolymer, unexpectedly, iron did not fill in the cavities, thus implying that it was “dispersed” in the polymeric matrix. Electronic microdiffraction documented that both polymers exhibited a proto-crystallinity, likely induced by thermal heating. Full article