Search Results (92)

In this study, we couple precise interface engineering via alternating current electrophoretic deposition (AC–EPD) with performance-enhancing structural transformation via annealing, enabling the development of high-performance, stable, and tunable Mn-based cathodes for aqueous zinc-ion batteries (ZIBs). Using AC–EPD to fabricate Mn(BTC) (BTC = 1,3,5-benzenetricarboxylic acid) cathodes followed by thermal annealing to synthesize MOF-derived Mn₃O₄ offers a synergistic approach that addresses several key challenges in aqueous ZIB systems. The Mn₃O₄ cathode prepared via AC–EPD from Mn(BTC) exhibited a remarkable specific capacity of up to 430 mAh/g at a current density of 200 mA/g. Interestingly, the capacity continued to increase progressively with cycling, suggesting dynamic structural or interfacial changes that improved Zn²⁺ transport and utilization over time. Such capacity enhancement behavior during prolonged cycling at elevated rates has not been observed in previously reported Mn₃O₄-based ZIB systems. Kinetic analysis further revealed that the charge storage process is predominantly governed by diffusion-controlled mechanisms. This behavior can be attributed to the intrinsic characteristics of the Mn₃O₄ phase formed from the MOF precursor, where the bulk redox reactions involving Zn²⁺ insertion require ion migration into the electrode interior. Even though the electrode was processed as an ultrathin film with enhanced electrolyte contact, the charge storage remains limited by solid-state ion diffusion rather than fast surface-driven reactions, reinforcing the diffusion-dominant nature of the system. Full article

Coordination-driven Cu(I) complexes constitute an interesting class of materials with rich opto-electronic properties and diverse applications. Various homo- and heteroleptic Cu(I) complexes have been reported in the literature. In continuation with our quest for new materials, we report herein two novel coordination-driven self-assembled Cu(I) complexes: the homoleptic (1) and the heteroleptic (2) complexes based on the 6,6′-bis(phenylethynyl)-2,2′-bipyridine (L1) and 2,9-dimethyl-1,10-phenanthroline (dmph) ligands. L1 was prepared by a Pd(II)-catalyzed Sonogashira cross-coupling reaction between phenylactylene and 6,6′-dibromo-2,2′-bipyridine. Homo- and heteroleptic Cu(I) complexes were obtained by the self-assembly of L1 and dmph ligands. Complexes (1) and (2) were obtained in high yields, and are soluble in common organic solvents and stable at room temperature over a long period of time. The optical (absorption and emission) properties of both complexes were evaluated. The optical properties in solution are a function of the ligands and varied for the complexes. Complex (2) was also characterized by single-crystal X-ray diffraction and the intermolecular interaction was studied using Hirschfeld surface analysis. In the solid state, complex (2) exhibited four-coordinate distorted tetrahedral geometry around Cu(I). Density functional theory (B3LYP/6-311++G(d,p) was utilised to determine various molecular descriptors. Full article

Enzymatic modification of Kraft lignin under alkaline conditions was investigated using bilirubin oxidase (BOD) in borate buffer (pH 10). Control solubilization without enzyme addition revealed a notable increase in molar mass (up to 1.7-fold) and potential borate complexation with lignin hydroxyl groups, as evidenced by thermogravimetric and ¹¹B NMR analyses. BOD treatments induced substantial polymerization, with molar mass increases of up to 4-fold for insoluble fractions after 24 h, while soluble fractions exhibited progressive increases over 5 days. Quantitative ³¹P NMR showed reductions in aliphatic and phenolic hydroxyl groups by 20%, suggesting oxidative coupling reactions, particularly through 4-O-5′ and 5-5′ linkages. Solid-state ¹³C NMR confirmed structural changes associated with polymerization. Dynamic light scattering (DLS) indicated the presence of colloidal aggregates, potentially explaining challenges in HSQC NMR signal acquisition. These findings highlight the efficacy of bilirubin oxidase in catalyzing lignin polymerization and underscore the structural impact of borate–lignin interactions in alkaline media, paving the way for advanced lignin valorization strategies. Full article

Finding reliable, sustainable, and economical methods for addressing the relentless increase in plastic production and the corresponding rise in plastic waste within terrestrial and marine environments has garnered significant attention from environmental organizations and policymakers worldwide. This study presents a comprehensive analysis of the low-heating-rate thermal degradation of high-density polyethylene (HDPE) plastic in conjunction with date seed powder (DSP), utilizing thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA/FTIR), machine learning convolutional deep neural networks (CDNNs), multiple linear regression model (MLRM) and thermokinetics. The TGA/FTIR experimental measurements indicated a synergistic interaction between the selected materials, facilitated by the presence of hemicellulose and cellulose in the DSP biomass. In contrast, the presence of lignin was found to hinder degradation at elevated temperatures. The application of machine learning CDNNs facilitated the formulation and training of learning algorithms, resulting in an optimized architectural composition comprising three hidden neurons and employing 27,456 epochs. This modeling approach generated predicted responses that are closely aligned with experimental results ($R^2~0.939$) when comparing the responses from a formulated MLRM model ($R^2~0.818$). The CDNN models were utilized to estimate interpolated thermograms, representing the limits of experimental variability and conditions, thereby highlighting temperature as the most sensitive parameter governing the degradation process. The Borchardt and Daniels (BD) model-fitting and Kissinger–Akahira–Sunose (KAS) model-free kinetic methods were employed to estimate the kinetic and thermodynamic parameters of the degradation process. This yielded activation energy estimates ranging from 40.419 to 91.010 kJ·mol⁻¹ and from 96.316 to 226.286 kJ·mol⁻¹ for the selected kinetic models, respectively, while the D2 and D3 diffusion models were identified as the preferred solid-state reaction models for the process. It is anticipated that this study will aid plastic manufacturers, environmental organizations, and policymakers in identifying energy-reducing pathways for the end-of-life thermal degradation of plastics. Full article

A pyridine-fused triazapentalene shows weak fluorescence in solution and is readily accessible via nitrene-mediated cyclization. In this study, a modified Cadogan reaction was used to synthesize HetATAP 1. Palladium-catalyzed reactions have been used as post-functionalization methods. Interestingly, modified Suzuki cross-couplings with various boronic acids resulted in poor to moderate yields of HetATAPs 2–5 which were arylated at the azole moiety. Direct CH arylation of HetATAP 1 gave the products with the same regiochemistry in satisfactory yields. The structures of HetATAPs 2–5 were confirmed using NMR analysis. In addition, the photophysical properties of HetATAPs 1–5 were studied under various conditions. Particularly, the emission of HetATAPs 2–5 is enhanced in the solid and aggregate state. Full article

In this research, we employed a high-entropy approach in tungsten-bronze-structured ferroelectric ceramics, preparing Sr_0.4Ba_0.6(Zr_0.2Ti_0.2Sn_0.2Ta_0.2Nb_0.2)₂ (denoted as SBN40-H) ceramics through the traditional solid-state reaction technique. By utilizing the high-entropy approach, the resulting SBN40-H ceramics demonstrated extremely fine grains, averaging 0.58 μm in size. Furthermore, these ceramics possessed a high bandgap of 3.35 eV, which, when combined with the small grain size, contributed to a remarkable breakdown strength of 570.01 kV/cm. The dielectric characteristics demonstrated typical relaxation behavior and outstanding temperature stability, with a capacitance temperature coefficient (TCC) of less than 5% within the temperature range of 111–317 °C. Additionally, the SBN40-H ceramics exhibit slim P–E loops with negligible hysteresis, which is considered to be related to the existence of weakly coupled relaxors. This results in exceptional overall energy-storage properties in the SBN40-H ceramics, exhibiting a notable recoverable energy density (W_rec) of 2.68 J/cm³ and an efficiency (η) of 93.7% at 390 kV/cm, and finally achieving a remarkable temperature stability in terms of energy-storage performance with variations in W_rec and η being less than 3.5% and 4.4% from 25 to 150 °C. It is worth noting that the high-entropy approach is highly effective in reducing grain size, increasing the breakdown field strength and enhancing the dielectric temperature stability of tungsten-bronze-structured ferroelectric ceramics. Full article

Palladium (Pd) is a 4d transition metal with electronic configuration [Kr] 4d¹⁰ 5s⁰, and it is one of the most widely studied metals in the periodic table due to its versatile catalytic role in organic synthesis. The choice of ligands that can coordinate with Pd sites plays a crucial role in the progress of the reaction. Due to the coexistence of multiple oxidation states (Pd(0)/Pd(II)), the active Pd sites of the catalysts can participate in various stages of the coupling reaction. The Pd-catalyzed C-C coupling reactions proceed through four steps: (1) oxidative addition of the reactant to the catalytic site, (2) transmetallation, (3) rearrangements of ligand centers and (4) reductive elimination to the coupling products. For the heterogeneous Pd nanocatalysts, active Pd sites are often strongly bound (chelated) with the solid catalyst surfaces. In this review, we have highlighted the advancements made in the heterogeneous Pd nanocatalysts with an emphasis on the types of different classes of porous solids, which could ligate with the Pd centers via strong covalent bonds. The high specific surface areas and small Pd sites of these nanocatalysts provide a larger number of catalytic sites and thus facilitate the reaction. Mechanistic aspects of the C-C cross-coupling reactions are discussed in the context of the structure–reactivity relationship. Full article

We report herein that bis(tricyclic) aromatic enes (BAEs) consisting of 6-6-6-membered frameworks such as acridine, xanthene, thioxanthene, and thioxanthene-S,S-dioxide act as a new class of organic luminophores that exhibit blue-to-green fluorescence in the solid state and in polymer film with good to excellent quantum yields. The BAEs were prepared by the palladium-catalyzed double cross-coupling reaction of phenazastannines or 10,10-dimethyl-10H-phenothiastannin with 9-(dibromomethylene)xanthene, 9-(dibromomethylene)thioxanthene, or 9-(dibromomethylene)-9H-thioxanthene-10,10-dioxide. Microcrystals or powder samples of the BAEs exhibited brilliant fluorescence with good to high quantum yields (Φ = 0.45–0.88). Furthermore, more efficient emission of blue-to-green light (Φ = 0.59–0.91) was observed for the BAEs dispersed in the poly(methyl methacrylate) (PMMA) films. Density functional theory (DFT) calculations suggest that the photo-absorption of the (thio)xanthene moiety-containing BAEs proceeds via π–π* transitions, whereas the optical excitation of 10,10-dioxido-9H-thioxanthene moiety-containing BAEs involves an intramolecular charge transfer from the acridine/thioxanthene part to the electron-accepting 10,10-dioxido-9H-thioxanthene moiety. Full article

To maintain the carbon dioxide concentration below the no-return threshold for climate change, we must consider the reduction in anthropic emissions coupled to carbon capture methods applied in synergy. In our recent papers, we proposed a green and reliable method for carbon mineralization using ascorbic acid aqueous solution as the reducing agent for carbon (IV) to carbon (III), thus obtaining oxalic acid exploiting green reagents. Oxalic acid is made to mineralize as calcium (as the model cation) oxalate. Oxalates are solid-state reservoirs suitable for long-term carbon storage or carbon feedstock for manufacturing applications. The carbon mineralization reaction is a double-step process (carbon reduction and oxalate precipitation), and the carbon capture efficiency is invariably represented by a double-slope curve we formerly explained as a decrease in the reducing effectiveness of ascorbic acid during reaction. In the present paper, we demonstrated that the reaction proceeds via a “pure CO₂-capture” stage in which ascorbic acid oxidizes into dehydroascorbic acid and carbon (IV) reduces to carbon (III) and a “mixed” stage in which the redox reaction competes with the degradation of ascorbic acid in producing oxalic acid. Despite the irreversibility of the reduction reaction, that was demonstrated in abiotic conditions, the analysis of costs according to the market price of the reagents endorses the application of the method. Full article

New Nd³⁺-doped cadmium molybdato-tungstates with the chemical formula of Cd_1−3x▯_xNd_2x(MoO₄)_1−3x(WO₄)_3x (where x = 0.0283, 0.0455, 0.0839, 0.1430, 0.1875, 0.2000, 0.2500, and ▯ denotes a vacant site in the crystal lattice) were successfully synthesized by the high-temperature solid state reaction method, using CdMoO₄ and Nd₂(WO₄)₃ as the initial reactants. The structure and change in their lattice parameters as a function of Nd³⁺ ion concentration were investigated by the XRD (X-ray diffraction) method. The surface morphology and grain size of the doped materials were characterized by SEM (scanning electron microscopy). Their thermal properties and initial reactants were analyzed by DTA-TG (differential thermal analysis coupled with thermogravimetry) techniques. The optical properties of the Nd³⁺-doped cadmium molybdato-tungstates, such as optical band gap, were determined by UV–vis–NIR (ultraviolet–visible–near infrared) spectroscopy. The EPR (electron paramagnetic resonance) technique provided information on the type of magnetic interactions between Nd³⁺ ions. Full article

While hundreds of complexes of the general formula [Ni(η⁵-C₅H₅)(NHC)(X)] exist (NHC = a N-heterocyclic carbene, X = Cl, Br, I), none is yet known with X = F. We attempted to prepare such a species by reacting nickelocene with imidazolium fluorides. Three imidazolium fluorides (ImH)⁺ F⁻ [Im = (N,N′-bis-(R)-imidazolium: 1a, IMe, R = Me; 1b, IMes, R = 2,4,6-trimethylphenyl; 1c, IPr, R = 2,6-diisopropylphenyl)] were prepared and characterized by spectroscopic methods. In addition, the salts 1b [(IMesH)⁺ F⁻] and 1c [(IPrH)⁺ F⁻] were subjected single-crystal X-ray diffraction experiments. The reactions of these imidazolium fluorides with nickelocene did not lead to [Ni(η⁵-C₅H₅)(NHC)(F)] species. Instead, the reaction of 1a [(IMeH)⁺ F⁻] and 1b [(IMesH)⁺ F⁻] with nickelocene led to the salt 2 [Ni(η⁵-C₅H₅)(IMe)₂]⁺ F⁻ and to the square planar complex 3atrans-[NiF₂(IMes)₂] respectively. Both complexes were characterized spectroscopically and by single crystal X-ray diffraction. All four X-ray diffraction studies reveal hydrogen bonding and hydrogen interactions with the F atom or anion, and in some cases with solvent molecules of crystallization, and these phenomena are all discussed. Complex 2, in particular, exhibited a wide range of interesting H-bonded interactions in the solid state. Complexes 2 and 3a were tested as catalysts for Suzuki–Miyaura coupling but were not promising: complex 2 was inactive, and while 3a did indeed catalyze the reaction, it gave widely diverging results owing to its instability in solution. Full article

Pentafluorophenyl copper(I)–biarylsulfoxide complexes, existing as [Cu(C₆F₅)]₄L₂, both in solution and in the solid state, were prepared and thoroughly characterized. Subsequently, the photochemistry of the complexes was explored, showing inherent photoreactivity of the biarylsulfoxide moiety within the coordination sphere of the copper. Photoinduced cross-coupling reactions between the anthryl moiety of bis-anthracenylsulfoxide and pentafluorobenzene, and synthesis of Cu₂O (cuprite), were demonstrated. Full article

In the process of particle erosion and electrochemical corrosion interaction, the electrolyte flow state change, product film destruction, and matrix structure change caused by particle impact affect the electrochemical corrosion process. Such transient, complex physical and electrochemical changes are difficult to capture because of the short duration of action and the small collision area. The peak, step time, and recovery time in this transient step cycle can indirectly reflect the smoothness and reaction rate of the electrochemical reaction system, and thus characterize the resistance to scouring corrosion coupling damage of metals in liquid–solid two-phase flow. In this study, in order to obtain the electrochemical response at the moment of particle impact, electrochemical monitoring experiments using a specially designed miniature three-electrode system were used to test step-critical values, including step potential, current, and resistance, among others. Meanwhile, an electrochemical step model under particle impact considering boundary layer perturbation was developed. The experimental results reflect the effect law of particle impact velocity and particle size on the peak step and recovery period. Meanwhile, the effect of particle impingement on the electrochemical step of stainless steel in different electrolyte solutions was obtained by comparing the step curves in distilled water and Cl-containing water. The connection between the parameters in the electrochemical step model and in the particle impact, as well as the effect of the variation of these parameters on the surface repassivation process are discussed in this paper. By fitting and modeling the test curves, a new mathematical model of electrochemical step-decay under single-particle impact was obtained, which can be used to characterize the change pattern of electrochemical parameters on the metal surface before and after the impingement. Full article

High-performance photovoltaic devices require active photoanodes with superior optoelectric properties. In this study, we synthesized neodymium ruthenate, Nd₂Ru₂O₇ (NRO), and gadolinium ruthenate pyrochlore oxides, Gd₂Ru₂O₇ (GRO), via the solid-state reaction technique, showcasing their potential as promising candidates for photoanode absorbers to enhance the efficiency of dye-sensitized solar cells. A structural analysis revealed predominantly cubic symmetry phases for both materials within the Fd-3m space group, along with residual orthorhombic symmetry phases (Nd₃RuO₇ and Gd₃RuO₇, respectively) refined in the Pnma space group. Raman spectroscopy further confirmed these phases, identifying distinct active modes of vibration in the predominant pyrochlore oxides. Additionally, a scanning electron microscopy (SEM) analysis coupled with energy-dispersive X-ray spectroscopy (EDX) elucidated the morphology and chemical composition of the compounds. The average grain size was determined to be approximately 0.5 µm for GRO and 1 µm for NRO. Electrical characterization via I-V measurements revealed that these pyrochlore oxides exhibit n-type semiconductor behavior, with conductivity estimated at 1.5 (Ohm·cm)⁻¹ for GRO and 4.5 (Ohm·cm)⁻¹ for NRO. Collectively, these findings position these metallic oxides as promising absorber materials for solar panels. Full article

Two series of novel [1,2,4]triazolo[4,3-c]- and [1,2,4]triazolo[1,5-c]quinazoline fluorophores with 4′-amino[1,1′]-biphenyl residue at position 5 have been prepared via Pd-catalyzed cross-coupling Suzuki–Miyaura reactions. The treatment of 2-(4-bromophenyl)-4-hydrazinoquinazoline with orthoesters in solvent-free conditions or in absolute ethanol leads to the formation of [4,3-c]-annulated triazoloquinazolines, whereas [1,5-c] isomers are formed in acidic media as a result of Dimroth rearrangement. A 1D-NMR and 2D-NMR spectroscopy, as well as a single-crystal X-ray diffraction analysis, unambiguously confirmed the annelation type and determined the molecular structure of p-bromophenyl intermediates and target products. Photophysical properties of the target compounds were investigated in two solvents and in the solid state and compared with those of related 3-aryl-substituted [1,2,4]triazolo[4,3-c]quinazolines. The exclusion of the aryl fragment from the triazole ring has been revealed to improve fluorescence quantum yield in solution. Most of the synthesized structures show moderate to high quantum yields in solution. Additionally, the effect of solvent polarity on the absorption and emission spectra of fluorophores has been studied, and considerable fluorosolvatochromism has been stated. Moreover, electrochemical investigation and DFT calculations have been performed; their results are consistent with the experimental observation. Full article