Search Results (42,564)

Exploring synthetic pathways for efficient photocatalysts has always been a major goal in catalysis. The performance of organic photocatalysts is affected by a variety of complex factors, and how to understand the structure–effect relationship is the key to designing efficient photocatalysts. This work explored the feasibility of constructing large-specific-surface-area conjugated microporous polymers (CMPs) based on stereoscopic units like spirobifluorene and achieving efficient photocatalytic activity by modulating the donor–acceptor (D-A) ratio with dibenzothiophene sulfone. Crosslinked pore structures were successfully constructed, and the specific surface area increased with the ratio of spirobifluorene. When the molar ratio of D-A was 1:20, polymer Spso-3 showed the highest photocatalytic hydrogen production activity, at 22.4 mmol h^–1 g^–1. The findings indicate that constructing D-A type CMPs should be a promising approach to improving the performance of photocatalytic water separation. The appropriate push–pull effect of the D-A structure promotes the photo-induced separation of electron–hole pairs, and the porous structure built on steric units offers ample space for catalytic reactions. This work could provide case references for structural design and the structure–effect relationship of efficient polymer photocatalysts. Full article

Lithium-ion batteries (LIBs) have been widely applied in electronic communication, transportation, aerospace, and other fields, among which separators are vital for their electrochemical stability and safety. Electrospun polyvinylidene fluoride (PVDF)-based separators have a large specific surface area, high porosity, and remarkable thermal stability, which significantly enhances the electrochemistry and safety of LIBs. First, this paper reviewed recent research hotspots and processes of electrospun PVDF-based LIB separators; then, their pivotal parameters influencing morphology, structures, and properties of separators, especially in the process of electrospinning solution preparation, electrospinning process, and post-treatment methods were summarized. Finally, the challenges of PVDF-based LIB separators were proposed and discussed, which paved the way for the application of electrospun PVDF-based separators in LIBs and the development of LIBs with high electrochemistry and security. Full article

The improved heat dissipation observed in 3D micro-ribbed tubes is primarily influenced by the intricate interplay of multiple structural parameters. Nevertheless, research into the coupling mechanisms of these multi-structural parameters remains constrained by the absence of effective methodology in numerical solutions. In the present work, a new 3D micro-rib structure based on discrete adjoint method is established. Firstly, the research examines the interplay of different parameters (such as arrangement, relative roughness height, angle of attack, and circumferential rows) on the thermo-hydraulic performance. It is noted that the heat transfer efficiency is notably impacted by the relative roughness height. And the arrangement methodology dictates the optimal positioning for heat transfer efficiency. An increase in the number of circumferential rows enhances fluid mixing, while the angle of attack plays a crucial role in the formation of longitudinal vortices. Secondly, the coupling optimization technique is employed to obtain the optimal structure featuring non-uniform relative roughness height by the developed numerical solution. Overall, in comparison to the smooth tube, the optimized ribbed tube exhibits a remarkable 64.9% enhancement in performance evaluation criteria. Finally, a notable enhancement of 10.65–22.78% is observed when comparing with the prevailing micro-rib structures. Full article

Additive manufacturing (AM) of components using material extrusion (MEX) offers the potential for the integration of functions through the use of multi-material design, such as sensors, actuators, energy storage, and electrical connections. However, there is a significant gap in the availability of electrical composite properties, which is essential for informed design of electrical functional structures in the product development process. This study addresses this gap by systematically evaluating the resistivity (DC, direct current) of 14 commercially available filaments as unprocessed filament feedstock, extruded fibers, and fabricated MEX-structures. The analysis of the MEX-structures considers the influence of anisotropic electrical properties induced by the selective material deposition inherent to MEX. The results demonstrate that composites containing fillers with a high aspect ratio, such as carbon nanotubes (CNT) and graphene, significantly enhance conductivity and improve the reproducibility of MEX structures. Notably, the extrusion of filaments into MEX structures generally leads to an increase in resistivity; however, composites with CNT or graphene exhibit less reduction in conductivity and lower variability compared to those containing only carbon black (CB) or graphite. These findings underscore the importance of filler selection and composition in optimizing the electrical performance of MEX structures. Full article

Branched fluorinated surfactants with creatively introduced acrylate in the hydrophilic group were designed and prepared by adopting perfluoro-2-methyl-2-pentene as the raw substrate. These new compounds showed excellent surface properties, and the surface tension of their aqueous solution at 25 °C could be below 20.00 mN/m at the critical micelle concentration. Compared with similar structures we have synthesized previously, these synthesized compounds exhibit a great improvement with regard to their molecular arrangement at the gas–liquid interface, their polymerizability, and the antibacterial properties of their polymer form, which can provide new ideas in the work to replace perfluorooctane sulfonate/perfluorooctanoic acid. Full article

Magnetic fluid hyperthermia, a minimally invasive localized therapy that uses heat generated by magnetic nanoparticles under an AC magnetic field, is a complementary approach for cancer treatment that is excellent due to its advantages of being noninvasive and addressing only the affected region. Still, its use as a stand-alone therapy is hindered by the simultaneous requirement of nanoparticle biocompatibility, good heating efficiency, and physiological safe dose. To overcome these limits, the biocompatible magnetic nanoparticles’ heating efficiency must be optimized. Iron oxide nanoparticles are accepted as the more biocompatible magnetic nanoparticles available. Therefore, in this work, superparamagnetic iron oxide nanoparticles were synthesized by a low-cost coprecipitation method and modified with starch and gum to increase their heating efficiency and compatibility with living tissues. Two different reducing agents, sodium hydroxide (NaOH) and ammonium hydroxide (NH₄OH), were used to compare their influence. The X-ray diffraction results indicate the formation of a single magnetite/maghemite phase in all cases, with the particle size distribution depending on the coating and reducing agent. Citric acid functionalized water-based ferrofluids were also prepared to study the heating efficiency of the nanoparticles under a magnetic field with a 274 kHz frequency and a 14 kAm⁻¹ amplitude. The samples prepared with NaOH display a higher specific loss power (SLP) compared to the ones prepared with NH₄OH. The SLP value of 72 Wg⁻¹ for the magnetic nanoparticles coated with a combination of starch and gum arabic, corresponding to an intrinsic loss power (ILP) of 2.60 nWg⁻¹, indicates that they are potential materials for magnetic hyperthermia therapy. Full article

Sprinkle formulations represent an interesting genre of medicinal products. A frequent problem, however, is the need to mask the unpleasant taste of these drug substances. In the present work, we propose the use of a novel sensor array based on solid-state ion-selective electrodes to evaluate the taste-masking efficiency of rosuvastatin (ROS) sprinkle formulations. Eight Multiple Unit Pellet Systems (MUPSs) were analyzed at two different doses (API_50) and (API_10), as well as pure Active Pharmaceutical Ingredient (API) as a bitter standard. Calcium phosphate-based starter pellets were coated with the mixture containing rosuvastatin. Some of them were additionally coated with hydroxypropyl methylcellulose, which was intended to separate the bitter substance and prevent it from coming into contact with the taste buds. The sensor array consisted of 16 prepared sensors with a polymer membrane that had a different selectivity towards rosuvastatin calcium. The main analytical parameters (sensitivity, selectivity, response time, pH dependence of potential, drift of potential, lifetime) of the constructed ion-selective electrodes sensitive for rosuvastatin were determined. The signals from the sensors array recorded during the experiments were processed using Principal Component Analysis (PCA). The results obtained, i.e., the chemical images of the pharmaceutical samples, indicated that the electronic tongue composed of the developed solid-state electrodes provided respective attributes as sensor signals, enabling both of various kinds of ROS pellets to be distinguished and their similarity to ROS bitterness standards to be tested. Full article

Powders with a phase composition including syngenite (K₂Ca(SO₄)₂·H₂O) and/or calcium sulfate dihydrate (gypsum, CaSO₄·2H₂O) were synthesized from the powder of calcium carbonate (CaCO₃) and water solutions of potassium hydrosulfate (KHSO₄) of various concentrations (0.5 M, 1 M, and 2 M). A molar ratio of starting salts, KHSO₄/CaCO₃ = 2, was used to provide the formation of syngenite (K₂Ca(SO₄)₂·H₂O). But when using a 0.5 M water solution of potassium hydrosulfate (KHSO₄), the phase composition of the synthesized powder was presented by calcium sulfate dihydrate (gypsum, CaSO₄·2H₂O). When using 1 M and 2 M water solutions of potassium hydrosulfate (KHSO₄), the syngenite (K₂Ca(SO₄)₂·H₂O) was found as the predominant phase in synthesized powders. According to estimations made from thermal analysis data, powders synthesized using 1.0 M and 2.0 M water solutions of potassium hydrosulfate (KHSO₄) contained no more than 7.9 and 1.9 mass % of calcium sulfate dihydrate (gypsum, CaSO₄·2H₂O), respectively. The phase composition of products isolated from mother liquors via water evaporation consisted of syngenite (K₂Ca(SO₄)₂·H₂O) and potassium sulfate (arcanite, K₂SO₄). Synthesized powders can be used in preparation of biocompatible bioresorbable materials with phase compositions in the K₂O-CaO-SO₃-H₂O system; as matrix of thermo- or photo-luminescent materials; as components reducing the setting time and increasing the strength of sulfate cements; in the fertilizing industry; and also as components of Martian regolith simulants. Full article

Cobaltocenium-containing (co)polysiloxanes (Cc-PDMSs) with terminal and side groups were synthesized by the reaction of catalyst-free hydroamination between ethynylcobaltocenium hexafluorophosphate and polysiloxanes comprising amino moieties as terminal and side groups. The conversion of NH₂ groups in the polymers reaches 85%. The obtained (co)polysiloxanes “gelate” due to an increase in their molecular weight by approx. 30 times, when stored at room temperature over one week. “Gelated” Cc-PDMSs remain soluble in most polar solvents. The structure of Cc-PDMSs and the mechanism of “gelation” were established by ¹H, ¹³C{¹H}, ²⁹Si{¹H}, ¹⁹F{¹H}, ³¹P{¹H} nuclear magnetic resonance, infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies. As determined by cyclic voltammetry, Cc-PDMSs possess redox properties (Co^II/Co^III transitions at E_1/2 = −1.8 and −1.3 V before and after “gelation”, respectively). This synthetic approach allows to increase the molecular weights of the synthesized polysiloxanes functionalized with cobaltocenium groups easily, leading to their higher film-forming ability, which is desirable for some electronic applications. Cc-PDMSs can be utilized as redox-active polymer films in modified electrodes, electrochromic devices, redox-active coatings, and components for batteries. Full article

With the aim of meeting the growing demand for safe food, intelligent packaging has emerged, which monitors the conditions of the food and informs the consumer about its quality directly at the time of purchase. Among intelligent packaging options, colorimetric indicator films, which change color in response to changes in the food, such as the release of volatile compounds, have been widely studied. Among them, pH indicator films composed of dyes sensitive to small variations in the pH value of the food surface have received greater attention in recent years. Anthocyanins, which are natural pigments, have stood out as one of the most commonly used sources of dyes in the production of these indicator films. In this context, the present review aims to present an updated overview of research employing anthocyanins in indicator films, including their stability under different storage conditions, the influence of different polymers used in their production, and alternative techniques for maintaining stability. Full article

Precast concrete sandwich panels consist of two outer layers connected by a central connector and an inner insulating layer that enhances thermal and acoustic performance. A key challenge with these panels is eliminating thermal bridges caused by metallic connectors, which reduce energy efficiency. PERFOFRP connectors, made from perforated glass fiber-reinforced polymer (GFRP) sheets, have been proposed to address this issue. These connectors feature holes that allow concrete to pass through, creating anchoring pins that enhance shear resistance and prevent the separation of the concrete layers. This research aimed to evaluate the effect of the diameter and number of holes on the mechanical strength of PERFOFRP connectors. Three diameters not previously reported in the literature were selected: 12.70 mm, 15.88 mm, and 19.05 mm. A total of 18 specimens, encompassing 6 different configurations with varying numbers of holes, underwent push-out tests. The most significant resistance increase was a 15% gain over non-perforated connectors, observed in the configuration featuring three holes of 19.05 mm. The connections exhibited rigid and nearly linear behavior until failure. Full article

A carbon fiber-reinforced polymer (CFRP) is a common material utilized for the enhancement in reinforced concrete (RC) constructions. Previous research indicates that the bonding performance between a CFRP sheet and concrete determines whether the bonding of CFRP material is effective. However, the majority of existing research on the bonding performance of the CFRP–concrete interface is concentrated on static loading conditions. In order to clarify the effect of dynamic load on the bonding performance of the CFRP sheet–concrete interface, this study adopts the double-sided shear test method to carry out dynamic experimental research. The test findings reveal that the damage pattern of the CFRP sheet–concrete interface remains consistent across different loading rates. The ultimate bearing capacity increases as the strain rate increases. As the strain rate increases from 10⁻⁵ s⁻¹ to 10⁻² s⁻¹, the effect of bond length on ultimate bearing capacity increases by about 7%. As the strain rate increases, both the maximum strain of CFRP and the maximum interfacial shear stress demonstrate a corresponding increase, with respective increase rates of 60% and 20%. The effective bond length decreases by about 20% when the strain rate rises from 10⁻⁵ s⁻¹ to 10⁻² s⁻¹. Finally, a formula for calculating the dynamic effective bond length of a CFRP sheet, grounded in the Chen and Teng formula, has been proposed and verified. Full article

In recent years, numerous researchers have incorporated plant fibers into polymers to alter the thermal and mechanical properties of materials. Grapevines, considered agricultural waste, have led to burdens for farmers and environmental challenges due to their mass production. This study aims to reduce the brittleness of polylactic acid (PLA) by adding polybutylene succinate (PBS) as a toughening agent and employing grapevine fiber (GVF) as a biomass filler. Additionally, the influence of GVF, toughening agents, compatibilizers, and lubrication agents on the tensile strength, heat deflection temperature (HDT), and impact strength of the composites was examined. The findings revealed that the addition of 10% GVF and 5% PBS increased the impact and tensile strengths of PLA from 17.47 J/m and 49.74 MPa to 29.7 J/m and 54.46 MPa, respectively. Moreover, the HDT of the composites exceeded 120 °C when the GVF content was more than 40 wt%. Additionally, the inclusion of a compatibilizer and a lubrication agent enabled the composite containing 30% GVF to achieve tensile and impact strengths of 45.30 MPa and 25.52 J/m, respectively. Consequently, these GVF/PLA green bio-composites not only improve the mechanical and thermal properties of PLA but also promote the reuse of waste grapevines. Full article