Search Results (658)

Aniline (ANI) was electropolymerized on ITO substrates with different surface resistivities. The process was performed by cyclic voltammetry from an aqueous, homogeneous solution containing sulfuric acid and the aniline monomer using various numbers of cycles and scan rates. The resulting polymer films (PANI) were characterized by ATR-IR spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The influence of ITO surface resistivity on the electropolymerization process, the quality of the obtained PANI layers, and their optical properties was evaluated. Homogeneous PANI films were produced on ITO substrates with surface resistivities of 15–25 Ω/sq, encompassing both emeraldine salt and emeraldine base forms. Although the film’s growth was rapid, it also led to adhesion issues. In contrast, for ITO substrates with surface resistivities of 70–100 Ω/sq and 80–100 Ω/sq, the resulting films showed improved adhesion but were less homogeneous. Nevertheless, the conductive emeraldine salt form of polyaniline was successfully obtained. The conductive form of polyaniline was obtained without any additional modifications to the electropolymerization procedure. Notably, the literature provides no systematic analysis of electropolymerization on ITO substrates with different surface resistivities, which opens up new research opportunities and provides a basis for the rational design and optimization of PANI-based electro-optical coatings for advanced sensing applications. Full article

Slickwater fracturing has become an adopted technology for enhancing hydrocarbon recovery from unconventional, low-permeability reservoirs such as shale and tight formations, owing to its ability to generate complex fracture networks at a low cost. Polyacrylamide and polyacrylamide-based gels serve as key additives in these fluids, primarily functioning as drag reducers and thickeners. However, downhole environments of high-temperature (>120 °C) and high-salinity (>1 × 10⁴ mg/L) reservoirs pose challenges, leading to thermal degradation and chain collapse of conventional polyacrylamide, which results in performance loss. To address these limitations, synthesis methods including aqueous solution polymerization, inverse emulsion polymerization, and aqueous dispersion polymerization have been developed. This review provides an overview of molecular design methods aimed at enhancing performance stability of polyacrylamide-based polymers under extreme conditions. Approaches for improving thermal stability involve synthesis of ultra-high-molecular-weight polyacrylamide, copolymerization with resistant monomers, and incorporation of nanoparticles. Methods for enhancing salt tolerance focus on grafting anionic, cationic, or zwitterionic side chains onto the polymer backbone. The drag reduction mechanisms and gelation methods of these polymers in slickwater fracturing fluids are discussed. Finally, this review outlines research directions for developing next-generation polyacrylamide polymers tailored for extreme reservoir conditions, offering insights for academic research and field applications. Full article

Cadmium sulfide is an important II-VI semiconductor known for its valuable photocatalytic properties ascribable to its band gap energy, which allows light absorption in the visible domain. Nonetheless, the application of cadmium sulfide in wastewater organic pollutant degradation is restricted due to its high toxicity to humans, soil, and marine life. To address this issue, we developed new composite materials by depositing CdS on a bentonite support in a 1:9 mass ratio to develop a photocatalyst with lower toxicity. In the first step, bentonite was activated using an aqueous HCl solution; for the deposition of CdS powder, we proposed the trituration method and compared it with chemical precipitation and hydrothermal synthesis, using thioacetamide as a sulfide ion source. The modified bentonite underwent characterization using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, UV-Vis, and FTIR spectroscopy. The photocatalytic activity was tested in the degradation of Congo red (CR), a persistent diazo dye. The efficiency of removing CR with CdS–bentonite composites depended on the deposition method of CdS, and it was higher than that of pristine CdS and of only adsorption onto acid-activated bentonite. The photocatalytic degradation mechanism was estimated by the scavenger test using ethylenediaminetetraacetic acid disodium salt, ascorbic acid, ethanol, and silver nitrate as radical scavengers. Full article

The hydrophobic region of semaglutide makes it prone to aggregation in aqueous solution, which leads to serious interception in microfiltration. The influences of pH and low concentrations of salts (NaCl, CH₃COONa, Na₂SO₄ and (NH₄)₂SO₄) on the particle size and zeta potential of semaglutide aggregates were studied in this work. The results showed pH could change the zeta potential on the semaglutide surface, but the impact on semaglutide dispersion was limited. When salts were introduced into aqueous solution, NaCl had a more significant dispersion effect on semaglutide than other salts. Under pH 2.5 or pH 8.0 conditions, the addition of 0.01 mol/L NaCl reduced the average particle size of semaglutide aggregates to below 70 nm. The permeability of semaglutide in microfiltration increased from 60% to 86% under optimized conditions with the PES membrane (0.22 μm), and the adsorption loss also reduced 40%. In addition, this study compared the HPLC detection precision of semaglutide samples prefiltered with different microfiltration filters. Some semaglutide was intercepted by various microfiltration filters, resulting in serious detection errors. When semaglutide was dissolved in the aqueous solution containing 0.01 mol/L NaCl with pH 2.5, the detection error was controlled within 1%. Full article

The stability of physical and mechanical properties of highly filled swelling rubbers in polar and nonpolar liquids (oil, mineralized water) was studied. Nitrile butadiene rubber of BNKS-28 AMN grade served as the elastomer matrix, with sodium salt of carboxymethylcellulose (NaCMC) as the swelling filler. Oxal T-92, a mixture of dioxane alcohols (10–50 phr, step 10 phr), was used as a plasticizer due to its good thermodynamic miscibility with rubber (confirmed by Scatchard–Hildebrand calculations). Adding Oxal T-92 to NaCMC-filled compounds markedly reduced Mooney viscosity, improving processing through increased macromolecule mobility, without significantly affecting vulcanization kinetics—indicating chemical inertness toward crosslinking centers. Increasing Oxal T-92 from 10 to 50 phr reduced tensile strength from 4.1 MPa to 2.9 MPa. Swelling in aqueous solutions of varying mineralization was evaluated via volume and mass change. The optimal plasticizer content for high swelling with acceptable strength is 20–30 phr. After 3 days in oil and formation water, NaCMC-filled rubbers retained stable physical and mechanical properties. Full article

Mn⁴⁺-activated fluoride phosphors possess outstanding luminescent properties, making them highly suitable for applications in lighting and display technologies. However, the synthesis of such phosphors generally requires the use of large amounts of highly toxic aqueous HF, leading to serious environmental pollution. To eliminate the use of hazardous HF solution, a low-temperature molten salt method employing NH₄HF₂ was developed to synthesize the narrow-band red emitter Cs₂GeF₆: Mn⁴⁺ phosphor. Following the reaction, the product was washed with a dilute H₂O₂ solution to remove residual NH₄HF₂ and other impurities. The phase purity and morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, and the luminescence properties were examined via photoluminescence (PL) spectroscopy. The obtained phosphors exhibit bright red emission characteristics of Mn⁴⁺ under blue-violet excitation. Among them, Cs₂GeF₆: 0.08 Mn⁴⁺ shows the highest emission intensity, with an internal quantum efficiency (IQE) of 78%. A white light-emitting diode (WLED) fabricated by combining this phosphor with a blue chip and commercial Y₃Al₅O₁₂: Ce³⁺ (YAG) phosphor achieved a high luminous efficacy (LE) of ~146 lm/W, a correlated color temperature (CCT) of ~4396 K, and a color rendering index (Ra) of ~83, alongside excellent operational color stability. Full article

The performance of conventional bentonite-based drilling fluids is severely compromised in high-salinity and high-hardness brines, creating a need for salt-tolerant viscosifiers. This work provides a comprehensive performance evaluation of an activated palygorskite sourced from the Ventzia basin in Greece to be used as a high-performance additive for water-based drilling fluids. Six raw clay samples were mechanically processed and activated via extrusion and chemically treated with 2.25% MgO. Their rheological behavior and filtration properties were systematically investigated in three aqueous environments, (i) deionized water, (ii) API-standard salt water, and (iii) API-standard high-hardness salt water. The performance was benchmarked against that of commercial palygorskite products. The results demonstrated that the selected activated Greek samples exhibited excellent rheological properties, including higher viscosity, yield point, and thixotropic gel strength, comparable to those of the commercial benchmark. While the fluid’s rheology was suppressed by increasing salinity due to the flocculation of co-existing smectite, the best-performing Greek clays maintained a significant advantage, developing exceptionally robust gel structures critical for solid suspension in harsh conditions. Crucially, the same smectite flocculation mechanism proved highly beneficial for filtration control, leading to a significant reduction in fluid loss and the formation of a thin filter cake, particularly with the high-hardness brine. The findings confirm that activated Greek palygorskite is a technically viable, high-performance alternative to imported commercial materials, offering a sustainable solution for formulating resilient drilling fluids for challenging environments. Full article

Pollution of water resources with hazardous substances of anthropogenic origin (e.g., synthetic dyes, heavy metal ions) is currently one of the most important environmental issues, and the development of not only effective and economical but also eco-friendly methods of removing these substances from aqueous solutions is one of the greatest challenges. Among the various separation methods, techniques based on the utilization of different types of polymer membranes have gained increasing interest due to their usually high efficiency, the materials’ stability and reusability, and the possibility of using “green” components for their formation. Recent research efforts have been concentrated, inter alia, on the application of natural polysaccharide polymers (e.g., cellulose, alginates, starch, cyclodextrins) and their derivatives to produce well-performing membranes. Appropriately composed polysaccharide-based membranes under optimal process conditions enable effective separation of dyes, salts, and metal ions (e.g., often with a rejection rates of >95% for dyes and metal ions and <7% for salts). This review concerns the latest developments in the formation and utilization of novel polysaccharide-based membranes for the separation of synthetic dyes and metal ions from aqueous solutions and suspensions, with emphasis on their most important advantages, limitations, and potential impact on the environment and sustainability. Full article

Mn⁴⁺-doped fluoride red phosphors are widely used in white LED lighting and display applications due to their excellent luminescent properties. However, their synthesis relies heavily on highly toxic aqueous hydrofluoric acid, which not only causes severe environmental and soil/water pollution but also makes it difficult to control the microstructure of the products due to the rapid reaction rate. In this study, low-melting-point NH₄HF₂ was used as the molten salt, with KMnO₄ and MnF₂ as manganese sources, to synthesize the red phosphor K₃AlF₆: Mn⁴⁺ via the molten salt method. After the reaction, impurities such as NH₄HF₂ were removed by washing with a dilute H₂O₂ solution. The microstructure, photoluminescence properties, thermal quenching behavior, and application in warm white light-emitting diodes (W-LEDs) of the K₃AlF₆: Mn⁴⁺ phosphors were investigated. The results indicate that the phosphors prepared by this method consist of a single pure phase. By adjusting the molten salt content, the morphology of the product can be transformed from nanoparticle-like to nanorod-like structures. All products exhibit the characteristic red emission of Mn⁴⁺ under blue and violet light excitation, with the optimally doped sample achieving an internal quantum efficiency (IQE) of 69% under blue light excitation. The combination of the obtained K₃AlF₆: Mn⁴⁺ with the yellow phosphor YAG enabled the fabrication of W-LEDs. These W-LEDs achieved a color rendering index (Ra) of 86.8, a luminous efficacy (LE) of 77 lm/W, and a correlated color temperature (CCT) of 3690 K, along with excellent color stability under operating conditions. Full article

This study introduces an innovative hybrid approach combining salting-out and adsorption for the highly efficient removal of crystal violet (CV) dye from aqueous solutions. The method leverages high-ionic-strength brine discharge from the Complex of El-Outaya (CEO, ENASEL, Biskra, Algeria) and micro-mesoporous biochar derived from calves’ horn cores (BHC-800). Results demonstrate that both undiluted and diluted brine significantly enhance CV removal, while BHC-800, with a surface area of 258 m² g⁻¹, exhibits a maximum Langmuir adsorption capacity of 106.1 mg g⁻¹ (at 20 °C ± 2). Thermodynamic analysis confirms a spontaneous (ΔG° < 0) and exothermic (ΔH° = −0.86 kJ mol⁻¹) process, with increased interfacial disorder (ΔS° = 93.53 J mol⁻¹ K⁻¹). The synergistic effect of salting-out and adsorption achieved ~99.8% removal of CV at an initial concentration of 1000 mg L⁻¹. Furthermore, BHC-800 exhibited excellent reusability, maintaining high adsorption efficiency over multiple cycles. Economic assessment revealed operational costs of 0.45–0.89 US$ m⁻³ for 60% brine discharge. Biochar production costs were 0.076–0.18 US$ kg⁻¹, translating to 7.5–17.2 (10⁻⁴ US$) per gram of CV removed. This dual strategy not only offers an eco-friendly and cost-effective solution for dye-laden water but also promotes the valorization of saline effluents and animal byproducts, addressing critical environmental challenges in industrial wastewater treatment. Full article

Samarium, a rare earth element, is crucial for advanced technological applications, particularly due to the exceptional magnetic properties of Sm_xCo_y intermetallics, discovered over 50 years ago. However, its growing significance and demand have highlighted concerns about scarce, commercially viable natural sources and the complex separation processes needed to isolate it from other lanthanides. In this context, electrodeposition has emerged as a versatile method for both synthesizing samarium materials and recovering the element. A major obstacle in applying electrolysis lies in the complex electrochemical behavior of samarium species, stemming from their highly negative electrochemical potential. While this limits the use of aqueous solutions, it also opens up possibilities for alternative solvents, such as molecular liquids, ionic liquids, deep eutectic solvents, and molten salts. The electrochemical properties of samarium have prompted exploration into electrodeposition techniques for material synthesis and recycling. This review discusses various aqueous and non-aqueous electrolyte compositions, different electrolysis modes, and the role of cathode substrates. It also shows the potential of electrolysis in the fabrication of various cathode products (metal, alloys/intermetallics, inorganic compounds), highlighting both challenges and opportunities in its practical implementation. Full article

Choline salts represent sustainable and safe electrolyte systems. In this study, an aqueous 1 M choline nitrate solution was employed to prepare hydrogel polymer electrolytes (HPE) via in situ photopolymerization. To enhance compatibility between the electrolyte and polymer matrix, choline methacrylate was synthesized and used as a functional monomer alongside HEMA and PEGDA. The photocurable formulation contained 70 wt.% electrolyte and 30 wt.% monomer mixture. Subsequent electrolyte uptake increased the electrolyte fraction in the HPE to 87 wt.%. The use of choline methacrylate enabled the formation of transparent HPE with favorable mechanical performance, showing puncture resistance of 0.33 N and 0.28 N at elongations of 7.9 mm and 4.4 mm for samples with 70 and 87 wt.% electrolyte, respectively. High ionic conductivity was achieved, reaching ~18 mS/cm and ~34 mS/cm for HPE with 70 and 87 wt.% electrolyte. Finally, a capacitor assembled with HPE containing 87 wt.% electrolyte demonstrated good operational parameters, confirming the applicability of this system in energy storage devices. This work highlights the potential of choline-based electrolytes and polymerizable choline derivatives as functional components for the design of efficient, safe, and environmentally friendly gel polymer electrolytes. Full article

The synthesis of a small library of fused Cyclic Aryl Amino Carbon (f-CArAC) carbene precursors in the form of 1,1,2,4-tetraaryl-1H-isoindol-2-ium triflate (6), (7-R) (R = ^tBu, CF₃) or 3,3-dimethyl-2,8-bis-arene-substituted-3,4-dihydro-isoquinolin-2-ium hydrogen-dichloride (8) and 2,4,8-tri(substituted)-isoquinolin-2-ium tosylate salts (12) has been achieved. All of them feature an arene incorporated on the annulated benzene ring of the corresponding heterocycle, introduced at the early stages of their synthesis via the Suzuki cross-coupling reaction between 2,6-dibromo-benzaldehyde and the desired aryl boronic acid. The terphenyl-2′carbaldehyde by-products of this Suzuki reaction are useful starting points for the preparation of two new iminium iodide salts (10-R) (R = H, CF₃) as potential precursors to access ACyclic Amino Carbon (ACAC) carbenes. Compounds (6) and (7-^tBu) react readily with hydroxide either in THF or in a biphasic Et₂O/aqueous OH⁻ solution to produce the substituted isoindolinols (13) and (14), respectively. The thermal dehydration of the former generates the corresponding f-CArAC carbene in situ, which is trapped by Cu(I)Cl furnishing, a rare example of a two-coordinate Cu(I) complex (15) supported by this new ligand scaffold. Full article

High-pressure intrusion of water and LiCl aqueous solutions at different concentrations in hydrophobic STT-type zeosil was studied for possible applications in absorption and storage of mechanical energy. The water is intruded at a pressure of 35 MPa and remains trapped in the pores after pressure release, which corresponds to bumper behavior with total energy absorption. The use of LiCl solution leads to a change in system behavior, regardless of the concentration investigated (10, 15, or 20 M). Its intrusion is mainly reversible, but a small part of the intruded liquid remains in the pores after the first intrusion–extrusion cycle, which corresponds to a mixed behavior of bumper and shock absorber. The intrusion pressure rises strongly with an increase in salt concentration and reaches 227 MPa for a LiCl 20 M solution; the stored energy of 27 J/g can be achieved. The characterization of STT-type zeosil before and after intrusion–extrusion tests by structural and physicochemical methods shows that silanol defects are formed both under the intrusion of water and LiCl solutions. The relationship between zeosil structure and intrusion–extrusion characteristics is discussed by comparing the results obtained with those of other structural types of zeosils. Full article

This study investigates the physicochemical processes in aqueous solutions treated with a high-current (up to 300 A) pulsed multispark discharge. Pulse length was 2 μs at a 50 Hz repetition rate. The discharge occurred within bubbles of argon injected between the stainless-steel electrodes at the constant flow rate. The erosion of electrode material during the discharge led to iron and other alloy components entering the liquid. Optical emission spectra confirmed the erosion of electrode material (Fe, Cr, Ni atoms and ions). EDTA and its disodium salt were used in order to study their effect on the metal particle formation process. Treatment with deionized water led to an increase in conductivity and the generation of hydrogen peroxide (up to 1200 µM). In contrast, the presence of EDTA and its disodium salt drastically altered the reaction pathways: the H₂O₂ yield decreased, and the solution conductivity dropped substantially for the acidic form of EDTA, while the decrease was minor for EDTA-Na₂. This effect is attributed to the buffered chelation of eroded metal ions, forming stable Fe-EDTA complexes, as confirmed by a characteristic absorption band at 260 nm. The results demonstrate the critical role of complex-forming agents in modulating plasma–liquid interactions, shifting the process from direct erosion products to the formation of stable coordination compounds. Full article