Search Results (10,319)

The photo-thermochemical cycle (PTC) for water splitting offers a sustainable method for hydrogen production by efficiently utilizing solar energy. This study explored the use of CeO₂ as a catalyst in the PTC system to enhance hydrogen yield. A nanostructured CeO₂ catalyst was synthesized via the sol-gel method, achieving an H₂ yield of 8.35 μmol g⁻¹ h⁻¹. Stability tests over five cycles showed consistent yields between 7.22 and 8.35 μmol g⁻¹ h⁻¹. Analysis revealed that oxygen vacancies (V_Os) increased after the photoreaction and depleted during the thermal reaction, which aligns with the expected PTC mechanism for hydrogen production. Single-factor experiments highlighted that photoreaction duration mainly influenced V_Os generation, while thermal duration and temperature impacted V_Os consumption and intermediate reaction rates. A response surface methodology (RSM) model predicted optimal conditions for maximum H₂ yield (8.85 μmol g⁻¹ h⁻¹) with a photoreaction duration of 46.6 min, thermal duration of 45.4 min, and thermal temperature of 547.2 °C. Full article

Pt on carbon black (Pt/C) has been widely used as a catalyst for both ORR and hydrogen oxidation reaction (HOR), but its stability is compromised due to carbon corrosion and catalyst poisoning, leading to low Pt utilization. To address this issue, this study suggests replacing carbon black with graphene in the catalyst layer. The importance of this work lies in the detailed examination of novel electrocatalysts with high electrocatalytic activity for large-scale power generation. In this paper, we discuss the use of regulatory techniques like structure tuning and composition optimization to construct nanocatalysts impregnated with noble and non-noble metals on graphene supports. Finally, it highlights the limitations and advantages of these nanocatalysts along with some future perspectives. Our objective is that this summary will help in the research and rational design of graphene-based nanostructures for efficient ORR electrocatalysis. The results of this study showed that the performances of graphene-based catalysts show high electrochemical active surface areas for Pt-Fe/GNPs and Pt-Ni/GNPs catalysts (132 and 136 m² g⁻¹, respectively) at 100 operating cycles. Also, high current densities and power densities were observed for Pt₃-Ni/G and Pt-Co/G catalysts used at the cathode. The values for current density were 1.590 and 1.779 A cm⁻², respectively, while the corresponding values for power density were 0.57 and 0.785 W cm⁻². Full article

The aim of this work is to incorporate lanthanide-cored upconversion nanoparticles (UCNP) into the surface of microengineered biomedical implants to create a spatially controlled and optically releasable model drug delivery device in an integrated fashion. Our approach enables silicone-based microelectrocorticography (ECoG) implants holding platinum/iridium recording sites to serve as a stable host of UCNPs. Nanoparticles excitable in the near-infrared (lower energy) regime and emitting visible (higher energy) light are utilized in a study. With the upconverted higher energy photons, we demonstrate the induction of photochemical (cleaving) reactions that enable the local release of specific dyes as a model system near the implant. The modified ECoG electrodes can be implanted in brain tissue to act as an uncaging system that releases small amounts of substance while simultaneously measuring the evoked neural response upon light activation. In this paper, several technological challenges like the surface modification of UCNPs, the immobilization of particles on the implantable platform, and measuring the stability of integrated UCNPs in in vitro and in vivo conditions are addressed in detail. Besides the chemical, mechanical, and optical characterization of the ready-to-use devices, the effect of nanoparticles on the original electrophysiological function is also evaluated. The results confirm that silicone-based brain–machine interfaces can be efficiently complemented with UCNPs to facilitate local model drug release. Full article

In coal mines, the mixture of coal dust and gas is more ignitable than gas alone, posing a high explosion risk to workers. Using the explosion tube, this study examines the explosion propagation characteristics and flame temperature of low-concentration gas and coal dust mixtures with various particle sizes. The CPD model and Chemkin-Pro 19.2 simulate the reaction kinetics of these explosions. Findings show that when the gas concentration is below its explosive limit, coal dust addition lowers the gas’s explosive threshold, potentially causing an explosion. Coal particle size significantly affects explosion propagation dynamics, with smaller particles producing faster flame velocities and higher temperatures. Due to their larger surface area, smaller particles absorb heat faster and undergo thermal decomposition, releasing combustible gases that intensify the explosion flame. The predicted yield of light gases from both coal types exceeds 40 wt% daf, raising combustible gas concentrations in the system. When accumulated reaction heat elevates the gas concentration to its explosive limit, an explosion occurs. These results are crucial for preventing gas and coal dust explosion accidents in coal mines. Full article

The aim of the present paper is to propose an innovative, one-step and sustainable process allowing us to obtain almost 10 kg/week of pure and crystalline simonkolleite nanoparticles (SK NPs) in only 8 min of reaction, working in water, under ambient conditions of pressure/temperature, guaranteeing at the same time low environmental impact and a high yield of NP production. In addition, the obtained NPs can also act as ZnO precursors at ambient temperature, and this result supports the sustainability of the process considering that, generally, the production of ZnO from SK occurred via annealing at high temperatures. The SK NPs appeared pure and crystalline, characterized by a highly uniform hexagonal lamellar feature. Each lamella is composed of an ordered assembly of very small monodispersed primary NPs, with a size in the range 3–8 nm. The SK NPs exhibited a surface area of up to 41 m²/g, the highest value recorded in the literature, revealing that pore size distribution mainly peaked between 3 and 20 nm. Full article

Lithium–sulfur (Li–S) batteries have emerged as a promising candidate for next-generation high-energy rechargeable lithium batteries, but their practical application is impeded by the sluggish redox kinetics and low sulfur loading. Here, we report the in situ growth of δ-MnO₂ nanosheets onto hierarchical porous carbon microspheres (HPCs) to form an HPCs/S@MnO₂ composite for advanced lithium–sulfur batteries. The delicately designed hybrid architecture can effectively confine LiPSs and obtain high sulfur loading up to 10 mg cm⁻², in which the inner carbon microspheres with a large pore volume and large specific surface area can encapsulate high sulfur content, and the outer MnO₂ nanosheets, as a catalytic layer, can improve the conversion reaction of LiPSs and suppress the shuttle effect. The thick HPCs/S@MnO₂ electrode with 7 mg cm⁻² sulfur loading delivers an areal capacity of 4.0 mAh cm⁻² at 0.1 C and provides stable cycling stability with a low-capacity decay rate of 0.063 % per cycle after 200 cycles at 0.1 C. Furthermore, a Li–S pouch cell with a capacity of 2.5 A h is fabricated and demonstrates high cycling stability. This work offers a feasible method to build advanced sulfur electrodes with high areal loading and sheds light on their commercial application in high-performance Li–S batteries. Full article

This article reports the preparation of a novel functionalized magnetic nanoadsorbent through an addition reaction between Fe₃O₄ nanoparticles coated with allyl silica gel and 4-pyridinyl ethylene. A detailed characterization of Fe₃O₄@SiO₂-yl-VP was conducted. Among them, in the infrared spectrum, we can easily see that the absorption peak of the C=C stretching vibration at 1660 cm⁻¹ in the raw material disappears after the addition reaction, indicating the successful grafting of polymer on the surface of silica gel. The appearance of N element in the EDS spectrum also proves the successful completion of the addition reaction and the successful synthesis of Fe₃O₄@SiO₂-yl-VP. At pH = 5 and pH = 7, it only takes half an hour for Fe₃O₄@SiO₂-yl-VP to achieve maximum adsorption capacities of 85.06 and 73.78 mg/g for Hg (II) and Pb (II), respectively. The adsorption process conforms to the Langmuir model and the pseudo-first- and pseudo-second-order kinetic models and can be reused 11 times, demonstrating excellent reusability. Full article

This study investigated the electro-mineralization of chloroquine (CQ) in a filter-press-type flow reactor using two BDD electrodes operating in batch recirculation mode. The optimal operating parameters were established using response surface methodology (RSM) and central composite rotatable design (CCRD) with three parameters: current density (j), initial pH (pH₀), and volumetric flow rate (Q), with the mineralization efficiency of (CQ) and specific energy consumption (SEC) as responses. Optimal operating parameters were j = 155.0 mA/cm², pH₀ = 9.75, and Q = 0.84 L/min within a reaction time of 9 h, leading to a maximum mineralization efficiency of CQ of 52.59% and a specific energy consumption of 15.73 kW/mg TOC, with a total operating cost of USD 0.18 per liter. Additionally, an ultra-high-performance chromatography study identified three by-products (4-amino-7-choloroquinoline, formic acid, and acid acetic) of CQ degradation. Furthermore, the phytotoxicity test indicates that the electrochemical wastewater proposed decreased the effluent’s phytotoxicity, and an increase in the percentage of Vigna radiata germination was observed. The carbon footprint of optimized electrochemical mineralization of chloroquine is 2.48 kg CO₂ eq., representing a 48% reduction in cumulative energy demand (CED) when the source of energy is a mixture of fossil fuels (50%), wind (25%), and photovoltaic (25%) energy. Full article

Percutaneous Coronary Intervention (PCI) is a treatment method that involves reopening narrowed arteries with a balloon catheter that delivers a cylindrical, mesh-shaped implant device to the site of the stenosis. Currently, by applying a coating to a bare metal stent (BMS) surface to improve biocompatibility, the main risks after PCI, such as restenosis and thrombosis, are reduced while maintaining the basic requirements for the mechanical behavior of the stent itself. In this work, for the first time, the development and optimization process of the spatial structure of the Co-Cr stent (L-605) with a graphene-based coating using cold-wall chemical vapor deposition (CW-CVD) to ensure uniform coverage of the implant was attempted. The CW-CVD process allows the coating of 3D structures, minimizing thermal stress on the surrounding equipment and allowing the deposition of coatings on temperature-sensitive materials. It produces uniform and high-purity films with control over the thickness and composition. The reduced heating of the chamber walls minimizes unwanted reactions, leading to fewer impurities in the final coating. The graphene layers obtained using Raman spectroscopy at different parameters of the CW-CVD process were verified, their properties were investigated, and the functional mechanical behavior of the studied graphene-covered stent was confirmed. In vitro, graphene-coated stents promoted rapid endothelial cell repopulation, an advantage over gold-standard drug-eluting stents delaying re-endothelialization. Also, full-range biocompatibility studies on potential allergic, irritation, toxicological, and pyrogenic reactions of new material in vivo on small animal models demonstrated excellent biocompatibility of the graphene-coated stents. Full article

Phosphate (P) is the plant macronutrient with, by far, the lowest solubility in soil. In soils with low P availability, the soil solution concentrations are low, often below 2 [µmol P/L]. Under these conditions, the diffusive P flux, the dominant P transport mechanism to plant roots, is severely restricted. Phosphate is sorbed into various soil solids, Fe/Al oxides, clay minerals and, sometimes overlooked, humic Fe/Al surfaces. The immobilization of P in soil is often the result of the diffusion of P into the internal surfaces of oxides or humic substances. This slow reaction between soil and P further reduces the availability of P in soil, leading to P fixation. The solubilization of soil P by root-released carboxylates is a promising way to increase the acquisition and uptake of P from P-fixing soils. Citrate and, sometimes, oxalate are effective with respect to additional P solubilization or P mobilization, which may help increase the diffusive P flux into the roots by increasing the P solution concentrations in the rhizosphere. The mobilization of humic-associated P by carboxylates may be an effective way to improve soil P solubility. Not only orthophosphate anions are mobilized by root-released carboxylates, but also higher phosphorylated inositol phosphates, as the main part of P esters in soil are mobilized by carboxylates. Because of the rather strong bonding of higher phosphorylated inositol phosphates to the soil solid phase, the mobilization step by carboxylates appears to be essential for plants to acquire inositol-P. The ecological relevance of P mobilization by carboxylates and its effect on the uptake of P by crops and grassland species are, at best, partially understood. Plant species which form cluster roots such as white lupin (Lupinus albus L.) or yellow lupin (Lupinus luteus L.) release high rates of carboxylates, mainly citrate from these root clusters. These plant species acquire fixed or low available P which is accessible to plants at rates which do not satisfy their P demand without P mobilization. And white lupin and yellow lupin make soil P available to other plants in mixed cropping systems or for subsequent plant species in crop rotations. The mobilization of P by carboxylates is probably also important for legume/grass mixtures for forage production. Species such as alfalfa, red clover or white clover release carboxylates. The extent of P mobilization and P uptake from mobilized P by legume/grass mixtures deserves further research. In particular, which plant species mostly benefit from P mobilization by legume-released carboxylates is unknown. Organic farming systems require such legume/grass mixtures for the introduction of nitrogen (N) by forage legumes into their farming system. For this agricultural system, the mobilization of soil P by carboxylates and its impact on P uptake of the mixtures are an important research task. Full article

The development and characterization of synthesis techniques for oxide materials based on ceria is a subject of extensive study with the objective of their wide-ranging applications in pursuit of sustainable development. The present study demonstrates the feasibility of controlled synthesis of Ce_1−xM_xO_2−δ (M = Fe, Ni, Co, Mn, Cu, Ag, Sm, Cs, x = 0.0–0.3) in combustion reactions from precursors comprising glycine, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and cellulose as organic components. Controlled synthesis is achieved by varying the composition of the precursor, the type of organic component, and the amount of organic component, which allows for the influence of the generation of high-density electrical charges and outgassing during synthesis. The intensity of charge generation is quantified by measuring the value of the precursor–ground potential difference. It has been demonstrated that an increase in the intensity of charge generation results in a more developed morphology, which is essential for the practical implementation of ceria as a catalyst to enhance contact with gases and solid particles. The maximum value of the potential difference, equal to 68 V, is obtained during the synthesis of Ce_0.7Ni_0.3O_2−δ with polyvinyl alcohol in stoichiometric relations, which corresponds to a specific surface area of 21.7 m² g⁻¹. A correlation is established between the intensity of gas release for systems with different organic components, the intensity of charge generation, morphology, and the value of the specific surface area of the samples. Full article

The esterase EstSIT01 from Microbacterium can catalyze the asymmetric hydrolysis of meso-dimethyl ester to produce the crucial chiral intermediate (4S, 5R)-hemimethyl ester for d-biotin synthesis. Despite its high yields and stereoselectivity, the low thermostability of EstSIT01 limits its practical application. Herein, two kinds of rational strategies were combined to enhance the thermostability of EstSIT01. Based on the Surface Residue Substitution (SRS) method, two variants (G215A and G316A) with improved thermostability and one mutant (G293A) with superior activity were identified from nine candidates. According to the Consensus Mutation method, two mutants (E301P and A332P) with enhanced thermostability were identified from six candidates. However, the combined mutation failed to yield mutants surpassing the best single mutant, E301P, in terms of thermostability. The combined mutant E301P/G215A and E301P/G215A/G293A exhibited a slight enhancement in enzyme activity relative to E301P, while also exhibiting improved thermostability compared to the wild-type EstSIT01. Compared with the wild-type esterase, the thermal inactivation half-lives (t_1/2) of mutant E301P were enhanced 1.4-fold, 2.4-fold and 1.8-fold at 45 °C, 55 °C, and 65 °C, respectively. The optimal reaction temperature and pH for mutant E301P remained consistent with those of the wild type, at 40 °C and 10.0, respectively. The K_m of E301P was 0.22 ± 0.03 mM and the k_cat was 5.1 ± 0.28 s⁻¹. Further analysis indicated that the free energies of G215A, G293A and E301P were decreased by 0.91, 0.308 and 1.1049 kcal/mol, respectively, compared to the wild-type EstSIT01. The interaction analysis revealed that the substitution of glutamic acid with proline at position 301 enhanced the hydrophobic interactions within the protein. The decreased free energies and the increased hydrophobic interactions were well correlated with the enhanced stability in these mutants. Full article

Electrodialysis (ED) has already been applied to recover nickel in galvanizing processes, allowing nickel recovery and the production of a treated effluent with demineralized water quality. However, the growth in ED use is still limited by the production and commercialization of ion-selective membranes, currently limited to a few large companies. Therefore, this paper presents the development of homogeneous cationic and anionic membranes made from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) for ED use. Cationic membranes were prepared by the sulfonation reaction of PPO under different experimental conditions (PPO:H₂SO₄ molar ratio and reaction time). Anionic membranes were prepared by the bromination reaction of PPO, followed by the amination reaction. The membranes were characterized for their chemical and electrochemical properties, including ion exchange capacity, conductivity, thermal stability, and surface morphology. The optimal conditions for cationic membrane sulfonation were achieved with a 1:4.4 PPO:H₂SO₄ molar ratio, and a reaction time of 0.5 h. For anionic membranes, the best results were obtained with bromination, with a PPO:NBS (N-Bromosuccinimide) molar ratio of 1:0.5, followed by 14 days of amination. Overall, 91.8% chloride, 90.9% sulfate, and 85.5% nickel ion extraction was achieved, highlighting PPO as a promising polymer for the development of anionic and cationic ion-selective membranes for ED. Full article

Gold nanoparticles (Au NPs) are a promising target for research due to their small size and the resulting plasmonic properties, which depend, among other things, on the chosen reducer. This is important because removing excess substrate from the reaction mixture is problematic. However, Au NPs are an excellent component of various materials, enriching them with their unique features. One example is hydrogels, which provide a good, easily modifiable base for multiple applications such as cosmetics. For this purpose, various compounds, including hyaluronic acid (HA) and its derivatives, are distinguished by their high water-binding capacity and many characteristics resulting from their natural origin in organisms, including biocompatibility, biodegradability, and tissue regeneration. In this work Au NPs were synthesized using a green chemistry method, either by using onion extract as a reductant or chemically reducing them with sodium citrate. A complete characterization of the nanoparticles was carried out using the following methods: Fourier-Transform Infrared Spectroscopy (FT-IR), Electrophoretic (ELS), and Dynamic Light Scattering (DLS) as well as Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). Their antioxidant activity was also tested using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The results showed that the synthesized nanoparticles enrich the hydrogels with antioxidant properties and new surface properties (depending on the reducing agent, they can be more hydrophilic or hydrophobic). Preliminary observations indicated low cytotoxicity of the nanomaterials in both liquid form and as a hydrogel component, as well as their lack of penetration through pig skin. The cosmetic properties of hydrogel masks were also confirmed, such as increasing skin hydration. Full article

Supercapacitors are a kind of energy storage device that lie between traditional capacitors and batteries, characterized by high power density, long cycle life, and rapid charging and discharging capabilities. The energy storage mechanism of supercapacitors mainly includes electrical double-layer capacitance and pseudocapacitance. In addition to constructing multi-level pore structures to increase the specific surface area of electrode materials, defect engineering is essential for enhancing electrochemical active sites and achieving additional extrinsic pseudocapacitance. Therefore, developing a simple and efficient method for defect engineering is essential. Atomic layer deposition (ALD) technology enables precise control over thin film thickness at the atomic level through layer-by-layer deposition. This capability allows the intentional introduction of defects, such as vacancies, heteroatom doping, or misalignment, at specific sites within the material. The ALD process can regulate the defects in materials without altering the overall structure, thereby optimizing both the electrochemical and physical properties of the materials. Its self-limiting surface reaction mechanism also ensures that defects and doping sites are introduced uniformly across the material surface. This uniform defect distribution is particularly profitable for high surface area electrodes in supercapacitor applications, as it promotes consistent performance across the entire electrode. This review systematically summarizes the latest advancements in defect engineering via ALD technology in supercapacitors, including the enhancement of conductivity and the increase of active sites in supercapacitor electrode materials through ALD, thereby improving specific capacitance and energy density of the supercapacitor device. Furthermore, we discuss the underlying mechanisms, advantages, and future directions for ALD in this field. Full article