Search Results (82)

This work reports the electrochemical behavior of a nickel hydroxide electrode, electrodeposited in a deep eutectic solvent (DES), in alkaline solutions of varying composition, aiming to elucidate the influence of the cation (Na⁺ vs. K⁺), urea, and carbonate ions on the mechanism and kinetics of anodic processes. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to analyze the electrochemical responses of electrode processes in alkaline water electrolysis systems. For the urea oxidation reaction (UOR), the frequency-dependent characteristics were thoroughly characterized, and the impedance response was simulated according to the Armstrong–Henderson equivalent circuit. It was found that the addition of urea significantly transforms the impedance structure, sharply reducing the polarization resistance and increasing the pseudo-capacitive component of the constant phase element at low frequencies, indicating activation of the slow steps of urea oxidation via a direct mechanism and the formation of an extended adsorptive surface. It was demonstrated that, unlike conventional alkaline electrolysis where KOH-based systems are generally more effective, urea-assisted systems exhibit superior performance in NaOH-based electrolytes, which provides more favorable kinetics for the electrocatalytic urea oxidation process. Furthermore, the accumulation of carbonate ions was shown to negatively affect UOR kinetics by increasing polarization resistance and partially blocking surface sites, highlighting the necessity of controlling electrolyte composition in practical systems. These findings open new opportunities for the rational design of efficient urea-assisted electrolyzers for green hydrogen generation. Full article

Porous Ni, Ni–Ir, and Ni–Pt electrodes were prepared on Ni substrates by molten-salt Al co-deposition followed by dealloying. SEM/EDS and XRD confirmed a Raney-type porous network with Ir or Pt present across the layer. A urea oxidation reaction (UOR) was tested in 1 M NaOH + 0.33 M urea by cyclic voltammetry and chronoamperometry at +0.40 V vs. SCE (60 min). Smooth Ni showed near-zero current. Porous Ni resulted in ~11 mA cm⁻² initially and ~9 mA cm⁻² after 60 min. Porous Ni–Ir started at ~7 mA cm⁻² and fell to ~2 mA cm⁻² within 5 min, indicating fast deactivation, likely due to Ir-oxide formation that suppresses the Ni²⁺/Ni³⁺ redox couple. Porous Ni–Pt remained at ~11 mA cm⁻² over 60 min, consistent with a stable Ni–Pt effect in which Pt aids urea adsorption/activation while Ni provides the redox path for oxidation. Overall, Pt improves UOR performance, whereas Ir lowers it under these conditions. Full article

The utilization of carbon dioxide (CO₂) for synthesizing value-added chemicals represents a promising environmentally sustainable strategy. Herein, we synthesized a series of Mn₂O₃ catalysts derived from metal-organic frameworks (MOFs) incorporating three different ligands—homophthalic tricarboxylic acid (H₃BTC), 1,4-benzenedicarboxylic acid (H₂BDC), and a combination of polyvinyl pyrrolidone (PVP) with H₃BTC—via a hydrothermal method for ethylene urea (EU) production from CO₂ and ethylenediamine (EDA). The Mn₂O₃ catalyst derived from the H₃BTC+PVP ligand system (designated MnTP) demonstrated superior catalytic performance, achieving 97% EDA conversion and 97% EU selectivity under mild conditions (100 °C, 1 min), which surpassed all previously reported catalysts under comparable conditions. The enhanced activity originated from structural improvements induced by the H₃BTC+PVP precursors, particularly the promotion of oxygen vacancies and Mn³⁺ species, thereby facilitating efficient CO₂ activation and binding. This work establishes a novel strategy for the sustainable conversion of CO₂ into high-value cyclic ureas through rational catalyst design. Full article

To address the issues of traditional gels in high-temperature reservoir leakage plugging, such as injection–retention imbalance, poor high-temperature stability, and insufficient thixotropy, this study developed a thixotropic polymer gel system via molecular design and component optimization, aiming to achieve excellent thixotropy, high strength, and wide temperature adaptability (80–140 °C) while clarifying its gelation mechanism. First, the optimal polymer was selected by comparing the high-temperature stability and crosslinking activity of AM/AMPS copolymer (J-2), low-molecular-weight acrylamide polymers (J-3, J-4), and AM/AMPS/NVP terpolymer (J-1). Then, the phenolic crosslinking system was optimized: hexamethylenetetramine (HMTA) was chosen for controlled aldehyde release (avoiding poor stability/dehydration) and catechol for high crosslinking efficiency (enhancing strength via dense crosslinking sites). Urea–formaldehyde resin (UF) was introduced to form a “polymer-resin double network,” improving high-temperature compression resistance and long-term stability. Cyclic shear rheological tests showed the gel system had a larger hysteresis area than the polymer solution, indicating excellent thixotropy before gelation. It gelled completely at 80–140 °C (gelation time shortened with temperature). At 120 °C, its viscosity was 7500 mPa·s, storage modulus (G′) 51 Pa, and loss modulus (G″) 6 Pa, demonstrating good shear thixotropy. The final system (1% J-1, 0.3% catechol, 0.6% HMTA, 15% UF) is suitable for high-temperature reservoir leakage plugging. Full article

Adenosine nucleotides and polyphosphates play a significant role in biochemistry, from participating in the formation of genetic material to serving as metabolic energy currency. In this study, we examine the stability and decomposition rates of adenosine phosphates—5′-AMP, 5′-ADP, and 5′-ATP (mentioned simply as AMP, ADP and ATP hereafter)—at temperatures of 22–25 °C, 50–55 °C, 70–75 °C, and 85–90 °C, at a pH of 4, over periods of 2 and 4 days, in both saltwater and ultrapure water, under unsealed and completely dried down conditions. We found that adenosine phosphates degrade rapidly under heat and dehydration, particularly at temperatures above 25 °C. Among the three compounds, AMP is the most stable, maintaining its integrity between 22 and 55 °C, whereas ATP begins to degrade at 22–25 °C and ADP is completely decomposed at temperatures above this range. Decomposition rates were analyzed using quantitative ³¹P-NMR, based on the detection of various phosphorus-containing species. AMP primarily hydrolyzed into phosphate, pyrophosphate and even formed 2′,3′-cAMP. In contrast, the condensed adenosine phosphates (ADP and ATP) hydrolyzed to AMP, phosphate, pyrophosphate, triphosphate, 5′-AMP and, in some cases, 2′,3′-cyclic adenosine monophosphate (2′,3′-cAMP). We also investigated the formation of these compounds in the presence of N-containing additives such as thiourea, urea, imidazole, and cyanamide at temperatures between 65 and 70 °C. Among these, cyanamide and urea were particularly effective in promoting the synthesis of adenosine monophosphates (AMPs) from phosphate and adenosine. The major products observed were 2′,3′,5′-AMPs and cyclic 2′,3′-AMPs. In some experiments, adenosine diphosphate (ADP) and dimeric nucleotide species were also detected. These findings suggest that moderately heated evaporating pools could facilitate the abiotic formation of AMPs. However, such environments would likely have been unsuitable for the long-term accumulation of these compounds due to continued degradation, though there would exist some level of these nucleotides at steady state. Full article

Plasma Electrolytic Polishing (PEP) is an advanced anodic process that enhances stainless steel surfaces through controlled electrochemical dissolution and plasma-mediated modification. This study demonstrates that PEP treatment of AISI 304 SS at 300 V in aqueous urea solution (3.0 wt.%)/NH₄NO₃ (0.25 wt.%) achieves remarkable improvements: surface roughness decreases by 54.6% (from 0.197 ± 0.023 μm to 0.0895 ± 0.0205 μm) with minimal mass loss (0.0035 g·cm⁻²) in just 20 min. Tafel analysis showed a 99% reduction in corrosion rate (0.00497 mm yr⁻¹) compared to untreated AISI 304 SS (0.094 mm yr⁻¹). Cyclic Potentiodynamic Polarization (CPDP) measurements indicated superior pitting resistance (E_pit = +0.423 vs. +0.486 V for PEP processing). XPS analysis elucidates the underlying mechanisms, showing a 91% increase in the Cr/Fe ratio (0.44 to 0.84) and complete transformation of surface oxides to protective Cr₂O₃ (57.34 wt.%) and Fe₃O₄ (55.88 wt.%), which collectively explain the enhanced corrosion resistance. Full article

An electrochemical immunosensor for the quantification of prostate-specific antigens (PSAs) using silver nanocrystals (AgNCs) is reported. The silver nanocrystals were synthesized using a conventional citrate reduction protocol. The silver nanocrystals were characterized using scanning electron microscopy (SEM) and field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, and small-angle X-ray scattering (SAXS). The proposed immunosensor was fabricated on a glassy carbon electrode (GCE), sequentially, by drop-coating AgNCs, the electro-deposition of EDC-NHS, the immobilization of anti-PSA antibody (Ab), and dropping of bovine serum albumin (BSA) to prevent non-specific binding sites. Each stage of the fabrication process was characterized by cyclic voltammetry (CV). Using square wave voltammetry (SWV), the proposed immunosensor displayed high sensitivity in detecting PSA over a concentration range of 1 to 10 ng/mL with a detection limit of 1.14 ng/mL and R² of 0.99%. The immunosensor was selective in the presence of interfering substances like glucose, urea, L-cysteine, and alpha-methylacyl-CoA racemase (AMACR) and it showed good stability and repeatability. These results compare favourably with some previously reported results on similar or related technologies for PSA detection. Full article

This study investigates the photoelectrochemical (PEC) performance of molybdenum-doped bismuth vanadate (Mo-doped BiVO₄) and its heterojunction with the BiOCl layer in glucose and urea sensing. Photoelectrochemical analyses, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealed that the formation of a heterojunction enhanced charge carrier separation. The impact of the interaction between the surface of the photoanode and analytes on sensing performance was systematically evaluated. Among the tested configurations, Mo-doped BiVO₄ exhibited superior glucose sensing with a limit of detection (LOD) of 0.173 µM, while BiVO₄/BiOCl demonstrated an LOD of 2.474 µM. In the context of urea sensing, Mo-doped BiVO₄ demonstrated an LOD of 0.656 µM, while BiVO₄/BiOCl exhibited an LOD of 0.918 µM. Notably, despite the enhanced PEC activity observed in heterostructured samples, Mo-doped BiVO₄ exhibited superior sensing performance, attributable to good interaction with analytes. The photocurrent response trends—an increase with glucose concentration and a decrease with urea concentration—were attributed to oxidation and adsorption phenomena on the photoanode surface. These findings underscore the critical role of photoanode surface engineering in advancing PEC sensor technology, paving the way for more efficient environmental and biomedical applications. Full article

Riociguat is a soluble guanylate cyclase (sGC) activator that increases the levels of cyclic guanosine monophosphate (cGMP). cGMP is known to play a key role in regulating kidney function. This research sought to investigate the possible protective effects of riociguat on the kidneys in the context of chronic kidney disease (CKD). CKD was induced in male Wistar rats through adenine administration. A total of 24 rats were allocated into four groups and administered treatments over a period of 35 days. Group 1 received a normal diet and a vehicle (carboxymethylcellulose (0.5%)), serving as the control. Group 2 received adenine (0.25% w/w) in the feed and a vehicle. Groups 3 and 4 received adenine in the feed (0.25% w/w) plus riociguat (3 mg/kg/day) and riociguat (10 mg/kg/day), respectively. Adenine administration significantly elevated systolic blood pressure, plasma creatinine, urea, and neutrophil gelatinase-associated lipocalin (NGAL). Furthermore, adenine reduced creatinine clearance and increased the urinary albumin-to-creatinine ratio and urinary N-Acetyl-β-D-Glucosaminidase (NAG). Histopathologically, adenine caused renal tubular necrosis and fibrosis. Furthermore, adenine elevated the plasma concentration of interleukins (IL-1β and IL-6) and tumor necrosis factor-alpha (TNF-α). Adenine significantly increased renal malondialdehyde (MDA) and reduced glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (TAC). Treatment with riociguat attenuated adenine-induced hypertension, improved kidney function, and ameliorated histopathological changes. Riociguat also reduced kidney injury markers, inflammation, and renal oxidative stress. The renoprotective effect of riociguat is probably due to anti-inflammatory and antioxidant actions. This indicates that riociguat may have the potential to slow the progression of kidney damage in chronic kidney disease (CKD). Full article

Detecting urea is crucial for diagnosing related health conditions and ensuring timely medical intervention. The addition of machine learning (ML) technologies has completely changed the field of biochemical sensing, providing enhanced accuracy and reliability. In the present work, an ML-assisted screen-printed, flexible, electrochemical, non-enzymatic biosensor was proposed to quantify urea concentrations. For the detection of urea, the biosensor was modified with a multi-walled carbon nanotube-zinc oxide (MWCNT-ZnO) nanocomposite functionalized with copper oxide (CuO) micro-flowers (MFs). Further, the CuO-MFs were synthesized using a standard sol-gel approach, and the obtained particles were subjected to various characterization techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy. The sensor’s performance for urea detection was evaluated by assessing the dependence of peak currents on analyte concentration using cyclic voltammetry (CV) at different scan rates of 50, 75, and 100 mV/s. The designed non-enzymatic biosensor showed an acceptable linear range of operation of 0.5–8 mM, and the limit of detection (LoD) observed was 78.479 nM, which is well aligned with the urea concentration found in human blood and exhibits a good sensitivity of 117.98 mA mM⁻¹ cm⁻². Additionally, different regression-based ML models were applied to determine CV parameters to predict urea concentrations experimentally. ML significantly improves the accuracy and reliability of screen-printed biosensors, enabling accurate predictions of urea levels. Finally, the combination of ML and biosensor design emphasizes not only the high sensitivity and accuracy of the sensor but also its potential for complex non-enzymatic urea detection applications. Future advancements in accurate biochemical sensing technologies are made possible by this strong and dependable methodology. Full article

Cobalt-based catalysts are recognized as promising electrocatalysts for oxygen reduction reactions (ORRs) in fuel cells that operate within acidic electrolytes. A synthesis process involving a cobalt complex, nanocellulose, and dopamine, followed by pyrolysis at 500 °C under a nitrogen atmosphere, was used to create a cobalt and nitrogen-doped carbonaceous material. Additionally, urea was incorporated to enhance nitrogen doping in the carbonaceous material. The morphology and structure of the material were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), where SEM unveiled dispersed metal oxides within the carbonaceous framework. Energy Dispersive X-ray Spectroscopy (EDS) analysis showed an even distribution of elements across the cobalt-doped carbonaceous material. X-ray Photoelectron Spectroscopy (XPS) analysis further highlighted significant alterations in the elemental composition due to pyrolysis. The electrochemical behavior of the cobalt-doped carbonaceous material, with respect to the oxygen reduction reaction (ORR) in an acidic medium, was investigated via cyclic voltammetry (CV), revealing an ORR peak at 0.30 V against a reversible hydrogen reference electrode, accompanied by a notably high current density. The catalyst’s performance was evaluated across different pH levels and with various layers deposited, showing enhanced effectiveness in acidic conditions and a more pronounced reduction peak with uniformly applied electrode layers. Rotating disk electrode (RDE) studies corroborated the mechanism of a four-electron reduction of oxygen to water, emphasizing the catalyst’s efficiency. Full article

The presented paper characterized the molten salt-modified Ni electrode with excellent catalytic activity towards alkaline urea electrooxidation reaction. The electrodes were modified by electrodeposition of Al from molten salt electrolytes containing NaCl-KCl-AlF₃ at a temperature of 750 °C and applied potential of −1.9 V. The porous surface was obtained by anodic polarization with a potential of −0.4 V until the anodic current was equal to 0 mAcm⁻². The prepared deposits’ structure, surface morphology, and composition were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Anodic polarization was applied to assess the electrocatalytic activity and elucidate the urea electrooxidation mechanism in 1 M KOH + 0.33 M urea solution. The nanocrystalline structure, fine grain size, and microcracks on the surface of the studied electrodes contributed to their notably high electrochemically active surface area (ECSA). The cyclic voltammetry in the non-Faradaic regions of the samples shows that molten salt modification can increase the double layer capacitance of bare Ni plates by around ten times, from 0.29 mFcm⁻² to 2.16 mFcm⁻². Polarization of the electrodes in urea-containing KOH solution with potential of +1.52 V shows a significant difference in catalytic performance. For the bare nickel sample, the registered current density from the urea electrooxidation reaction was around +1 mAcm⁻², and for the molten salt-modified one, it was +38 mAcm⁻², which indicates the fact that the molten salt surface treatment can be a promising tool in tailoring the electrochemical properties of materials. Full article

Transition metals such as nickel and cobalt as an alternative to Pt and Pd can be used for oxygen evolution reactions (OERs) and hydrogen production reactions (HERs) in alkaline environments, facilitating green hydrogen production as a sustainable alternative to fossil fuels. In this study, an NiCo₂O₄ catalyst was produced by a sono-hydrothermal method using urea as a hydrolysis agent. The electrochemical performance of the catalyst-coated NiFelt electrode was evaluated at different KOH concentrations (0.25, 0.5, and 1 M) and four operating temperatures in the interval of 20–80 °C. The electrode characteristics were investigated via electrochemical spectroscopy (cyclic voltammetry, EIS, multistep chronopotentiometry, multistep chronoamperometry) using two different reference electrodes (Ag/AgCl and Hg/HgO), to obtain insight into the anodic and cathodic peaks. XRD, SEM, EDS, and TEM analyses confirmed the purity, structure, and nanoscale particle size (20–45 nm) of the NiCo₂O₄ catalyst. The electrode showed symmetric CV with Ag/AgCl, making this reference electrode more appropriate for capacitance measurements, while Hg/HgO proved advantageous for EIS in alkaline solutions due to reduced noise. The overpotential of the catalyst-coated NiFelt decreased by 108 mV at 10 mA/cm² compared to bare NiFelt, showing a good potential for its application in anion exchange membranes and alkaline electrolyzers at an industrial scale. Full article

Fever is one of the most common clinical conditions and is characterized by pyrogenic infection, malignancy, inflammation, and tissue damage, among others. Ellagic acid (EA) can inhibit the expression of related proteins on the pathway by blocking the nuclear factor kappa-B(NF-κB) signaling pathway, inhibit the levels of pro-inflammatory factors interleukin-1β(IL-1β), interleukin-6(IL-6), and tumor necrosis factor-α(TNF-α), increase the level of anti-inflammatory factor IL-10, and effectively alleviate inflammatory symptoms. In addition, EA can also reduce the levels of malondialdehyde(MDA) and nitric oxide(NO) in the body, increase the activities of superoxide dismutase (SOD), glutathione (GSH), and catalase(CAT), scavenge oxidative free radicals, inhibit lipid oxidation, and achieve antipyretic and anti-inflammatory effects. The purpose of this study was to establish the relationship between EA and various inflammatory markers, such as TNF-α, IL-6, IL-1β, prostaglandin E2(PGE₂), and cyclic adenosine monophosphate(cAMP), and clarify the mechanism of the cyclooxidase-2(COX-2)/NF-κB signaling pathway. Combined with the metabolomics analysis, our study revealed the effects of EA on multiple endogenous biomarkers, reflecting the characteristics of a multi-component, multi-target, and multi-pathway mechanism. Compared to lipopolysaccharide (LPS)- treated animals, subsequent administration of EA significantly lowered the LPS-induced rectal temperature increase (p < 0.05 or p < 0.01), significantly increased serum SOD and GSH levels (p < 0.05 or p < 0.01), and significantly decreased serum MDA, IL-1β, IL-6, and TNF-α levels (p < 0.05 or p < 0.01). In addition, compared to LPS-treated animals, subsequent administration of EA significantly decreased cerebrospinal fluid cAMP and PGE₂ levels (p < 0.05 or p < 0.01), significantly decreased cAMP, significantly increased 5-HT levels (p < 0.05 or p < 0.01), and significantly down-regulated p-NF-κB p65 and COX-2 protein levels in the hypothalamus. Subsequent gas chromatography mass spectrometry(GC-MS) metabolite analysis indicated that 12 differential metabolites were detected in serum isolated 4 h after LPS treatment, and 10 differential metabolites were detected in serum collected 7 h after LPS treatment. Next, Pearson correlation analysis was used to systematically characterize the relationship between the identified metabolites and TNF-α, IL-6, MDA, SOD, PGE₂, and cAMP. The levels of propionic acid, pyridine, and L-valine were up-regulated by EA, which inhibited the expression of MDA, IL-1β, and TNF-α and increased the activity of GSH. The levels of inositol, urea, and 2-monopalmitin were down-regulated by EA, which inhibited the expression of MDA, IL-1β, and TNF-α, increased the activity of SOD and GSH, reduced the inflammatory response, and alleviated the oxidative stress state. Combined with the results of the metabolic pathway analysis, we suggest that the pathways of the galactose metabolism, synthesis and degradation of ketone bodies, as well as ascorbic acid and aldehyde acid metabolism are closely related to the antipyretic and anti-inflammatory effects of EA. Our study established the relationship between EA and various inflammatory markers, such as TNF-α, IL-6, IL-1β, PGE₂, and cAMP, and clarified the mechanism of the COX-2/NF-κB signaling pathway. Combined with the metabolomics analysis, our study revealed the effects of EA on multiple endogenous biomarkers, reflecting the characteristics of a multi-component, multi-target, and multi-pathway mechanism. Full article

This study presents the successful synthesis of a cesium–nickel–vanadium fluoride (CsNiVF₆) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance in green hydrogen production through urea electrolysis in alkaline media. The physicochemical characterizations revealed that the CsNiVF₆ exhibits a pyrochlore-type structure consisting of a disordered cubic corner-shared (Ni, V)F₆ octahedra structure and nano-sheet morphology with a thickness ranging from 10 to 20 nm. Using the CsNiVF₆ catalyst, the electrochemical analysis, conducted through cyclic voltammetry, demonstrates a current mass activity of ~1500 mA mg⁻¹, recorded at 1.8 V vs. RHE, along with low-resistance (3.25 ohm) charge transfer and good long-term stability for 0.33 M urea oxidation in an alkaline solution. Moreover, the volumetric hydrogen production rate at the cathode (bare nickel foam) is increased from 12.25 to 39.15 µmol/min upon the addition of 0.33 M urea to a 1.0 KOH solution and at a bias potential of 2.0 V. The addition of urea to the electrolyte solution enhances hydrogen production at the cathode, especially at lower voltages, surpassing the volumes produced in pure 1.0 M KOH solution. This utilization of a CsNiVF₆ pyrochlore nano-sheet catalyst and renewable urea as a feedstock contributes to the development of a green and sustainable hydrogen economy. Overall, this research underscores the potential use of CsNiVF₆ as a cost-effective nickel-based pyrochlore electrocatalyst for advancing renewable and sustainable urea electrolysis processes toward green hydrogen production. Full article