Transition Metal Chemistry最新文献

A green chemistry approach was employed to synthesize silver nanoparticles (Ag NPs) by Momordica dioica leaf extract as a dual-functioning bioreductant and stabilizing agent. To characterize Ag NPs, several techniques were employed, including UV–visible spectroscopy, scanning electron microscopy (FE-SEM), transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Ag NPs were successfully synthesized, corroborated by UV–visible spectroscopy, showing a distinctive surface plasmon resonance (SPR) absorption band centered at 425 nm, indicating nanoparticle formation. Subsequent characterization using FE-SEM and HR-TEM revealed that the Ag NPs possess a spherical morphology with an average size of 26 nm. The face-centered cubic (fcc) phase structure of silver was verified by the XRD analysis. FTIR and XPS analyses indicated the role of plant phytochemicals in the reduction and stabilization of Ag NPs. The synthesized Ag NPs exhibited good thermal stability as determined by TGA and DSC. The Ag NPs demonstrated notable antibacterial effects on Escherichia coli, Bacillus subtilis, and Staphylococcus aureus, with the greatest effectiveness seen against S. aureus. Furthermore, the Ag NPs showed dose-dependent antibiofilm activity against S. aureus, with a 75% reduction in biofilm formation at a concentration of 300 µg/mL. To evaluate the catalytic efficiency of the synthesized nanoparticles, the catalytic degradation of methylene blue, Congo red, and 4-nitrophenol was investigated. The current research focuses on creating a method for producing Ag NPs that is both environmentally friendly and cost-effective, utilizing the leaf extract of M. dioica. This eco-friendly synthesis method employs the plant extract as a natural reducing and stabilizing agent, thus avoiding the use of harmful chemicals typically involved in traditional synthesis techniques. The Ag NPs produced through this process are anticipated to be biocompatible and stable, making them ideal for use in biomedical and environmental contexts. The nanoparticles are assessed for their antibacterial, antibiofilm, and catalytic properties, with a particular focus on their potential for microbial control and the breakdown of environmental pollutants.

New mononuclear copper(II) complexes [Cu(L1)Cl₂] ([Cu]-1), [Cu(L2′))Cl₂] ([Cu]-2) and [Cu(L3)(NO₃)₂] ([Cu]-3) with imidazole-based ligands {4,4′-((2-phenyl)methylene)bis(2-ethyl-5-methyl-1H-imidazole)} (L1), {3-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)-4-chlorophenol} (L2) and {2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)phenol} (L3) are synthesized and fully characterized by a variety of techniques. Furthermore, the molecular structures of complexes [Cu]-1 and [Cu]-2 are established by single-crystal X-ray structure analysis. [Cu]-1 and [Cu]-2 show distorted tetrahedral geometry around central metal atom.

This study investigates the kinetics of molybdenum (Mo) extraction from spent catalysts using citric acid as a leaching agent, emphasizing its efficiency under varied process conditions. The influence of solid-to-liquid (S/L) ratio, pH, and temperature was systematically examined, revealing that the highest Mo recovery was achieved at an optimal S/L ratio of 4 g/100 mL, pH of 1.5, and temperature of 90 °C, with a maximum Mo recovery of 88.37%. Kinetic modeling using a modified shrinking core model (SCM) indicated a transition from a surface-controlled reaction to a diffusion-limited phase, with activation energies of 9.128 kJ/mol for the surface reaction and 44.4017 kJ/mol for diffusion through the ash layer. The findings underscore the viability of citric acid as an environmentally sustainable alternative to conventional inorganic acids, enhancing molybdenum recovery while minimizing hazardous waste. Further investigations into auxiliary reagents and advanced modeling techniques are recommended to optimize hydrometallurgical processing for spent catalyst recycling.

This study examines the electrochemical purification of indium from lead impurities using various organic complexing agents. Through the application of cyclic voltammetry (CV) and differential pulse voltammetry (DPV), the separation efficiency of citric (CA), oxalic (OA), and tartaric acids (TA) was evaluated. In general, all the agents assessed exhibited high separation coefficients, resulting in improved thermodynamic and kinetic parameters for indium deposition. The addition of complexing agents effectively inhibited lead recovery, thereby increasing the purity of indium in the cathodic deposits. ICP-MS analysis confirmed a substantial increase in indium purity, decreasing the Pb content in following CA < OA < TA (2.62 × 10^–5 > 2.54 × 10^–5 > 1.45 × 10^–5, respectively). These findings provide a foundation for optimizing electrolyte composition for the selective electrorefining of indium, presenting a scalable and environmentally sustainable alternative for the production of high-purity indium.

Water splitting is considered as the most effective green hydrogen production method in the near future. Among various catalysts, amorphous molybdenum sulfide (MoS_x) exhibits itself as an attractive Pt-free catalyst to promote the hydrogen evolution reaction (HER). In this research, we employed electrochemical quartz crystal microbalance (E-QCM) to track the mass fluctuation during HER operation. The mass loss of approximately 20% was recorded while holding the catalyst at -0.11 V vs RHE, indicating the material was activated prior to proton reduction. A drastic increase in HER catalytic performance with the 90 mV shifting of onset potential from −0.23 V vs RHE for pristine MoS_x to −0.145 V vs RHE for the activated material was recorded. The current density increases ca. 5 times from 5.02 to 25.02 mA/cm² at −0.3 V vs RHE (iR correction). The mechanism of catalyst activation was also proposed by the elimination of S atoms from the MoS_x polymeric structure generating H₂S and [Mo₃S₇] clusters that may serve as actual active sites for HER. The generated clusters then gradually dissolved in the solution causing catalyst degradation that diminished catalytic performance of MoS_x.

A Schiff base nickel(II) complex, bis{5-(Diethylamino)-2-[(methylimino)methyl]phenolato}-nickel(II), was synthesized using 4-(Diethylamino)salicylaldehyde, methylamine, and nickel chloride hexahydrate. Understanding the crystal structure and its characterization is essential for potential applications in catalysis, materials science, and coordination chemistry. The crystal was analyzed by single-crystal X-ray diffraction and was found to crystallize in a monoclinic crystal system with a P2₁/c space group. It was characterized using UV–vis, IR, ¹H and ¹³C NMR, mass spectrometry, and thermogravimetry (TG). The azomethine (–C=N) group was confirmed by a peak at 1591 cm⁻¹ from IR. The monomeric mass, m/z = 468 g mol⁻¹, was obtained from mass spectrometry. The complex was thermally stable up to 312 °C and melted between 215 and 219 °C. It produced a carbonaceous nickel(II) oxide (NiO/C) residue at 500 °C. The Hirshfeld surface study showed that the H…H interaction (66.68%) contributes the most to crystal packing, followed by C…H (21.7%), O…H (4.8%), and N…H (4.0%). The DFT study yielded a value of 3.79 eV for the HOMO–LUMO band gap (ΔE).

The remarkable cycle life substantial power storage capacity and rapid recharge capability of electrochemical capacitors, particularly supercapacitors, have garnered considerable attention from the scientific community. Recent findings have indicated that composite materials particularly those combining carbon with transition metal oxides are optimal for achieving significant performance in supercapacitors. The synthesis of high crystalline SrZrO₃/rGO has been successfully achieved using the hydrothermal method, and the resulting SrZrO₃/rGO electrode demonstrates a remarkable specific capacitance of 891 F/g at 1 A/g. The electrochemical impedance spectra were used to find the charge transfer resistance of the materials. The results suggest that SrZrO₃/rGO nanosheet could be effectively utilized for rapid charge and discharge processes in developed energy storage technologies.

Scientists and researchers are constantly striving to enhance the energy storage capacity, power density, and cycle life of supercapacitors. In this study, we comparatively analyse the electrochemical performance of molybdenum trioxide forming composites with graphite or tungsten trioxide or manganese dioxide for supercapacitor material application. The elementary behaviour is analysed using different characterization techniques like X-ray diffraction, FTIR, and SEM. The composites of MoO₃ with graphite and WO₃ demonstrate weaker performance while that with δ-MnO₂ shows excellent performance with a specific capacitance of 208 F/g at 10 mV/s. This enhancement is attributed to the synergistic effect between MoO₃ and δ-MnO2, stemming from the layered structure and faradaic redox activity of MnO2, which facilitates improved charge storage via pseudocapacitance. Moreover, δ-MnO₂ accounts for superior reversibility of the redox reactions compared to other samples, and the reduced Rct and ESR values suggest improved conductivity and lower internal resistance, which support fast electron and ion. The weaker performance of graphite and WO₃ is attributed to its irreversibility and the hindrance to the electrolytic ions. These findings underscore the potential of MoO₃/δ-MnO2 as a promising electrode material for advanced energy storage devices.

Reactions of ferrous or ferric sulphates with the chelating diamine ligands bpy (2,2'-bipyridine) and phen (1,10-phenanthroline) in methanol/water solution yielded two new complexes, a green Fe^III complex [Fe₂(bpy)₂(H₂O)₂O(SO₄)₂]·3H₂O 1 and dark red complex [Fe(phen)₃](SO₄)·8.4H₂O 2. Both complexes were characterized using chemical and spectroscopic methods (IR, UV–Vis). Single-crystal X-ray study showed that 1 exhibits molecular structure formed of dinuclear complex molecules comprising {Fe–O–Fe} structural unit with close distance between the deformed octahedrally coordinated Fe atoms (3.1857(8) Å) and the unit cell content is completed by water solvate molecules. The crystal structure of 2 is ionic and is formed of [Fe(phen)₃]²⁺ complex cation, sulphate anion and water solvate molecules. The temperature dependent magnetic study of dinuclear complex 1 revealed strong antiferromagnetic interaction between the two Fe^III atoms which both are in HS state at all temperatures. The theoretical calculations predict strong antiferromagnetic interaction in dimers, and the analysis of magnetic data yields J/k_B = −315.4 K. The thermal behaviour of both complexes 1 and 2 was studied in both oxidative (air) and inert (nitrogen) atmospheres. The thermal decomposition in all cases started with dehydration at 90 °C 1 and 80 °C 2; the dehydrations were followed by temperature dependent IR spectroscopy for complex 2. In both atmospheres, the solid residues consisted of nanosized oxides (α-Fe₂O₃), as corroborated by scanning electron microscopy, while energy-dispersive X-ray spectroscopy confirmed the homogeneity of the resulting oxides.

The present study effectively utilizes the Crassostrea angulata (oyster) marine waste shell to prepare biocompatible titanium (Ti) doped hydroxyapatite (Ti/HAp) through the most popular and widely researched precipitation technique. The prepared Ti/HAp sample was extensively characterized by FTIR, XRD, FE-SEM, EDX mapping, HR-TEM, together with SAED patterns. The extremely intense peak in XRD diffractograms and the absorption peaks in FTIR (groups such as PO₄³⁻, OH⁻, and CO₃²⁻) confirm the formation of crystalline hexagonal-shaped hydroxyapatite (35 nm) in the Ti/HAp matrix. The micrographs of FE-SEM and HR-TEM images at different magnifications portray the distinct rod-like structure of synthesized Ti/HAp. In addition to XRD results, the SAED pattern shows the crystalline nature of the synthesized Ti/HAp. The antibacterial properties and cell viability of the synthesized Ti/HAp composite were thoroughly investigated. The antibacterial activity of Ti/HAp was rigorously evaluated against two distinct bacterial strains: the gram-negative Escherichia coli and the gram-positive Staphylococcus saprophyticus. The cytocompatibility of Ti/HAp was thoroughly evaluated through an MTT assay, utilizing osteoblast cells, specifically the MG-63 cell line. The role of Ti in the antibacterial and cell viability activity of the product was assessed through suitable mechanisms. The cell viability decreases as Ti/HAp concentrations increase. It exhibits cell viability of 80% at the low concentration of 7.8 µg/mL. In both bacterial strains, Ti/HAp demonstrated good antibacterial activity at increasing doses. Consequently, the prepared Ti/HAp demonstrates excellent antibacterial activity and cell viability, making it suitable for various biomedical applications.