Search Results (108)

Biomass-templated spinel ferrite/carbon nanocomposites are promising electrode materials; however, dense carbon shells formed during low-temperature carbonization can block electrolyte access to active sites and impair electrochemical performance. The role of this carbon-shell passivation in biomass-derived ferrite/carbon composites remains largely unexplored. Here, we identify this limitation in a stepwise-synthesized NiFe₂O₄/rGO@C composite (NFC-S, BET surface area = 5.23 m² g⁻¹, ΔEp = 113.3 mV) and resolve it through a rationally designed one-pot optimization strategy in which urea simultaneously serves as a pore-forming agent and nitrogen precursor. The optimized composite (N-NFC-O) achieves a BET surface area of 186.39 m² g⁻¹—a 35.6-fold enhancement—with 70.1% micropore contribution and 3.13 at.% in-situ nitrogen doping. Electrochemically, ΔEp narrows to 72.3 mV and enables efficient NO₂⁻ oxidation with a ~70 mV cathodic shift, whereas NFC-S shows negligible catalytic response under identical conditions. As a proof of concept, differential pulse voltammetry (DPV) yields a nitrite sensitivity of 9.17 µA cm⁻² mM⁻¹ and a detection limit of 92.5 µM. Overall, this work identifies carbon pore accessibility as a key structural descriptor governing electrocatalytic performance in biomass-derived ferrite/carbon composites and provides a general design strategy for developing high-performance biomass-derived carbon/oxide hybrid electrodes. Full article

Composite hydrogel based on acrylic acid and acrylamide, modified with metal ions (Ni²⁺, Al³⁺, Fe²⁺, Fe³⁺) with concentration 0.3 wt%, were synthesized in water or polyethylene glycol (with a molecular weight of 400 Da) at three monomer ratios (7/3, 1/1, 3/7). Dynamic mechanical analysis shows that the equilibrium modulus of elasticity ($G_e$) of unmodified hydrogels increases with acrylamide content due to higher crosslinking density ($n_e$) and smaller cell size. ${AlCl}_3$ or ${NiCl}_2$ strengthen the structure ($G_e$ increases +53.5% in a 1/1 ratio), while iron salts cause softening (decreases to 90% when using ${FeC}_2{O}_4$). Partial replacement of polyethylene glycol reduces the elasticity but when using ${AlCl}_3$ happens synergistic increase $n_e$ 1.9 times in the ratio 3/7. The self-healing efficiency reaches ~100% for ${FeCl}_3$ in PEG gel in a ratio of 1/1 and 72.1% for ${Fe\left({NH}_4\right)}_2{\left({SO}_4\right)}_2$ hydrogel in 3/7. The electrical conductivity of hydrogels increases in the range of ${Al}^{3+}>{Ni}^{2+}>{Fe}^{3+}$, while matrix based on polyethylene glycol reduces the conductivity by an order of magnitude. For ${Ni}^{2+}$-containing samples, pinched hysteresis loops are observed in both water and polyethylene glycol. In contrast, ${Al}^{3+}$ causes rapid passivation in the water matrix, while in the matrix based on polyethylene glycol, the current–voltage characteristics follow ohmic behavior. The results demonstrate the possibility of directional regulation of the mechanical, electrical, and self-healing efficiency of hydrogels by selecting the ratio of monomers, the nature of the ion modifier, and the type of solvent. Full article

This study investigated the impact of cobalt/nickel-silicate loadings on graphitic carbon nitride at 10% and 20% doses, designated (CoNiSi-10) and (CoNiSi-20), for the removal of ciprofloxacin (CPF), a hazardous, bioaccumulative antibiotic. The synthesized composites were characterized in detail using SEM, EDX, TEM, N₂ adsorption–desorption, XRD, and FTIR techniques. The CoNiSi-10 and CoNiSi-20 exhibited CPF q_t values of 64 and 107 mg g⁻¹, respectively, which were consistent with the surface area results. Adsorption kinetics indicated that CPF uptake on CoNiSi-10 and CoNiSi-20 fitted the Lagergren model, with the liquid-film and intraparticle-diffusion mechanisms co-governing CPF sorption. The isotherm investigations indicated CPF adsorption on CoNiSi-10 and CoNiSi-20 aligned with the Langmuir model, suggesting a homogeneous surface, while the Dubinin-Radushkevich results primarily indicated physisorption-based CPF removal. The thermodynamic analyses supported the physisorption outcome and indicated that CPF sorption onto CoNiSi-10 and CoNiSi-20 was endothermic. A five-cycle reusability test yielded average efficiencies of 94% and 96% for CoNiSi-10 and CoNiSi-20, respectively, and an after-sorption analysis indicated their stability and robustness. The ease of synthesis and excellent sorption performance may nominate CoNiSi-10 and CoNiSi-20 as promising adsorbents for treating pharmaceutically contaminated wastewater. Full article

This study was conducted to explore how varying the concentration of nano-La₂O₃ particles in the plating bath influences the morphology, constitution, and corrosion resistance of Ni-B composite coatings deposited on N80 carbon steel via electroless plating. The novelty of this work lies in the systematic investigation on the co-deposition behavior and grain refinement mechanism of nano-La₂O₃ in electroless Ni-B system, which has been rarely reported in previous studies. The microstructure and chemical composition of the coatings were characterized through a combination of SEM, EDS, XPS and XRD analyses. SEM confirmed that a dense Ni-B/La₂O₃ composite coating was formed, with a uniform thickness of approximately 10 μm, and the nano-La₂O₃ particles were evenly distributed. XPS analysis verified the presence of B, C, O, Ni and La, while XRD analysis revealed a refinement in crystalline size due to the addition of the nanoparticles. The corrosion resistance enhancement mechanism is attributed to the triple synergistic effect: nano-La₂O₃ pins grain boundaries and refines Ni-B grains to the minimum average size of 12.943 nm at the optimal concentration of 8 g·L⁻¹; the refined grain structure promotes the formation of a continuous and dense Ni(OH)₂ passive film; the uniformly dispersed nanoparticles act as physical barriers to block the penetration of corrosive media. Electrochemical measurements demonstrated that this coating exhibited outstanding anti-corrosion performance, as confirmed by a remarkably positive corrosion potential (E_corr = −0.37189 V) and a minimal corrosion current density (I_corr = 3.7524 μA/cm²). The results conclusively show that nano-La₂O₃ reinforcement effectively enhances the corrosion protection performance of electroless Ni-B alloy coatings. Full article

Nickel nanoparticles were synthesized via liquid-phase reduction of NiCl₂·6H₂O with N₂H₄·H₂O. The efficacy of different dispersing agents in preventing agglomeration was systematically compared, establishing a clear processing-dispersion correlation. Four different types of dispersants were selected to compare their effects on the microstructure and dispersibility of nano nickel powder. Among them, Ni nanoparticles prepared using sodium dodecyl sulfate (SDS) as dispersants exhibit superior microscopic morphology and dispersion. And then, the mass ratio between the precursor and dispersant was systematically optimized, resulting in spherical nickel nanoparticles with controllable particle size and favorable physical properties. When the mass ratio of SDS to Ni salt reached 150%, the prepared spherical Ni nanoparticles had the optimal dispersion and a minimum average particle size of 79 ± 12 nm. By estimating N_v, the concentration of nickel nanoparticles is about 2.15 × 10¹⁷ particles cm⁻³ at this ratio. After thermal treatment, the quality of the samples became stable beyond 415 °C with a maximum weight reduction of 6.75% at 150% SDS/Ni-salt ratio, and no residual surface sulfur was detected. The saturation magnetization of Ni nanopowders gently decreased with decreasing dispersant content from 35.3 emu·g⁻¹ to 31.6 emu·g⁻¹ at 300 K, while soft ferromagnetic behavior was maintained, which is more beneficial for the stability of multilayer ceramic capacitor performance. Full article

The influence of zirconia incorporation and template type on the physicochemical properties of NiMo/Al₂O₃-ZrO₂ catalysts was investigated for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the hydrogenation (HYD) of naphthalene (N). Catalysts were prepared by co-impregnation on supports synthesized via a sol-gel method using starch (A) and activated carbon (C) as structure-directing templates, followed by zirconium incorporation through a grafting procedure. The resulting materials were characterized by SEM–EDX, N₂ physisorption, H₂-TPR, XPS, HRTEM, and pyridine-FTIR. SEM-EDX confirmed homogeneous metal distributions and compositions close to nominal values (Mo = 20 wt%, Ni = 5 wt%, Zr = 11 wt%) with Ni/(Ni + Mo) = 0.30. N₂ adsorption–desorption isotherms correspond to type IV(a) with H3-H4 hysteresis loops, characteristic of mesoporous structures. After metal incorporation, surface areas decreased to 96 m² g⁻¹ for NiMo/Al₂O₃ and 81 m² g⁻¹ for Zr-modified catalysts, while the activated carbon-templated sample preserved a larger mesoporous volume (0.335 cm³ g⁻¹) and higher macroporosity (72%). H₂-TPR profiles indicated improved reducibility for Zr-containing catalysts. XPS revealed an increase of MoS₂ species from 45% in NiMo/Al₂O₃ to 75% in NiMo/Al₂O₃-ZrO₂(C), accompanied by a higher degree of sulfidation index (DSI) from 47.1% to 73.9%. HRTEM analysis of Zr-modified catalysts revealed longer MoS₂ slabs (11.8–12.1 nm) and higher edge-to-corner ratios (17–17.4) compared with NiMo/Al₂O₃ (6.2 nm; fe/fc = 8.2). Pyridine-FTIR showed a substantial increase in total acidity from 91 to 421 μmol g⁻¹ upon Zr addition. Catalytically, NiMo/Al₂O₃-ZrO₂(C) exhibited the highest HDS conversion (40%), reaction rate (10.5 × 10⁻⁹ mol s⁻¹ g⁻¹), and TOF (4.69 × 10⁻⁵ s⁻¹), whereas NiMo/Al₂O₃-ZrO₂(A) reached the highest naphthalene conversion (97.18%), with a reaction rate of 27.4 × 10⁻⁷ mol s⁻¹ g⁻¹ and TOF of 12.9 × 10⁻³ s⁻¹. These results demonstrate that Zr incorporation and the activated carbon template favored hydrodesulfurization, whereas the starch template promoted hydrogenation performance. Full article

The chlorophyll molecule is considered a low-cost material, easy to synthesize, and easily extracted from plant leaves. It exhibits high chemical stability, structural flexibility, and high absorbance ability at the visible range of electromagnetic radiation. In this work, the geometrical, electronic, and optical properties of pure, dissolved, and doped chlorophyll (C1) natural organic dye were computed by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The solvents considered include water (H₂O), acetone (C₂H₆O), dichloromethane (CH₂Cl₂), chloroform (CH₃Cl), and dimethyl-sulfoxide (DMSO) (C₂H₆OS). The solar photovoltaic parameters, such as light-harvesting efficiency (LHE), oscillation strength (f), free energy of electron injection (${\Delta \mathrm{G}}_{\mathrm{I}\mathrm{n}\mathrm{j}.}$) and regeneration (${\Delta \mathrm{G}}_{\mathrm{R}\mathrm{e}\mathrm{g}.}$), open-circuit voltaic (V_OC), and efficiency ($\eta$), were also investigated. The evaluated energy gap slightly shifted from 1.920 eV to 1.980 eV based on the solvent polarity, while the UV-Visible absorption spectrum red-shifted from 422.3 nm to 439.8 nm, improving the overall efficiency up to 21.5% in DMSO solvent. The (LHE) and (${\Delta \mathrm{G}}_{\mathrm{I}\mathrm{n}\mathrm{j}.}$) properties regarding Cl molecules improved up to 69.1% and −1.384 eV when dissolved in chloroform and DMSO solvents, respectively. Doping C1 molecule via metal transition atoms such as zinc (Zn), nickel (Ni) and copper (Cu) further modified the optical and photovoltaic performance. Doped C1 molecule via Cu atom shows the best photonic results, including the highest open-circuit voltage (V_oc) and conversion efficiency ($\mathrm{Ƞ}$), while the Ni-doped C1 dye displays the longest lifetime, 1.699 µs, and the highest electronic coupling constant, 1.975 eV; thus, it has the superior photovoltaic performance. These results demonstrate that both solvents and transition metal atom modification significantly improve C1 performance, making metal-doped C1 a promising low-cost and eco-friendly sensitizer for dye-sensitized solar cells (DSSCs). Full article

Trioctyl(alkyl)phosphonium chloride ionic liquids ([P_888n][Cl], n = 8, 14, and 16) were synthesized, characterized, and investigated for the extraction of Co, Ni, Mn, Mg, Zn, and Ca from chloride solutions. The three ionic liquids were very effective for the extraction of cobalt (over 95%) from solutions containing 1 g/L of Co(II) and 4 M HCl or NaCl. Equilibrium cobalt extraction was attained in less than 10 min at 25 °C using the most viscous ionic liquid [P₈₈₈₁₆][Cl]. Based on a speciation diagram for cobalt–chloride species and ultraviolet–visible spectrometric analysis of the phases, it was concluded that Co(II) extraction involved the extraction of the neutral species CoCl₂. Only at high chloride concentration, the anionic exchange mechanism involving $\mathrm{C}\mathrm{o}{\mathrm{C}\mathrm{l}}_4^{2-}$ was the most dominant. The stripping of the loaded ionic liquids can be carried out with water, and the stripped ionic liquids can be recycled up to five times maintaining their extraction effectiveness. In all of the conditions tested, the selectivity of [P_888n][Cl] ionic liquids for the extraction of cobalt over nickel was great, with a separation factor over 25,000 for 5M HCl solutions. Furthermore, very good selectivity for Co(II) over Mg(II) and Ca(II) extraction was also obtained. Conversely, Zn(II) can be selectively extracted over Co(II) and Mn(II) using only diluted [P₈₈₈₁₄][Cl]. Full article

Pyrolysis of plastic from waste electrical and electronic equipment (WEEE) is a promising method for producing value-added chemicals. However, flame retardants in WEEE can cause halogen contamination in pyrolysis oil, reducing its value. This work aims to develop an innovative catalytic hydrodehalogenation (CHD) protocol for the removal of chlorobenzene and bromobenzene. Iron sulphate heptahydrate (FeSO₄·7H₂O) and nickel ammonium sulphate hexahydrate ((NH₄)₂Ni(SO₄)₂·6H₂O) were used as catalysts, while sodium borohydride (NaBH₄) acted as a hydrogen donor for iron reduction. The novelty of the process lies in the generation of nano zero-valent iron (nZVI) that takes place within the CHD reactor (in situ) without the addition of strong acids. Various experimental set-ups were investigated to optimise the key process parameters (e.g., reagent concentrations). The optimal conditions—obtained in the autoclave at 30 °C with a 1:1 molar ratio of chlorobenzene to catalyst, omission of nickel salt, and 5 mmol of NaBH₄—resulted in a 75% reduction in chlorobenzene and complete removal of bromobenzene. The results confirm the effectiveness of the proposed protocol for the dehalogenation of chlorobenzene and bromobenzene, which can facilitate the valorization of pyrolysis oils derived from plastic waste, contributing to the closure of the WEEE cycle (the widest and fastest-growing source of global waste with significant environmental, social and economic impacts). Full article

Developing sustainable and molecularly selective adsorbents for heavy-metal removal remains a critical challenge in water purification. Herein, we report a green molecular-engineering approach for fabricating aza-crown ether functionalized sodium alginate aerogels (ACSA) capable of highly selective Cu²⁺ capture. The aerogels were synthesized via saccharide-ring oxidation, Cu²⁺-templated self-assembly, and reductive amination, enabling the covalent integration of aza-crown ether motifs within a hierarchically porous biopolymer matrix. Structural analyses (FTIR, ¹³C NMR, XPS, SEM, TGA) confirmed the in situ formation of macrocyclic N/O coordination sites. Owing to their interconnected porosity and chemically stable framework, ACSA exhibited rapid sorption kinetics following a pseudo-second-order model (R² = 0.999) and a Langmuir maximum adsorption capacity of 150.82 mg·g⁻¹. The material displayed remarkable Cu²⁺ selectivity over Zn²⁺, Cd²⁺, and Ni²⁺, arising from the precise alignment between Cu²⁺ ionic radius (0.73 Å) and crown-cavity dimensions, synergistic N/O chelation, and Jahn-Teller stabilization. Over four regeneration cycles, ACSA retained more than 80% of its original adsorption capacity, confirming excellent durability and reusability. This saccharide-ring modification strategy eliminates crown-ether leaching and weak anchoring, offering a scalable and environmentally benign route to bio-based adsorbents that combine molecular recognition with structural stability for efficient Cu²⁺ remediation and beyond. Full article

In this study, a ternary Ni/Mg/g-C₃N₄ composite was synthesized via a controlled precipitation–calcination route and evaluated for its visible-light-assisted degradation of methylene blue (MB). The structural, morphological, and optical characteristics of the composites were systematically investigated using XRD, FT-IR, FESEM, BET, and UV–Vis analyses. The results confirmed the successful construction of Ni/Mg/g-C₃N₄ heterojunctions with strong interfacial coupling and enhanced surface porosity. Among all samples, the Ni/Mg/CN20 composite exhibited the highest activity, achieving 66% MB degradation within 180 min under visible light. This superior performance was attributed to synergistic effects arising from efficient interfacial charge transfer, broadened light absorption, and abundant active sites. The composite also displayed excellent thermal stability. This work demonstrates that the rational control of g-C₃N₄ loading plays a decisive role in tuning the physicochemical and catalytic properties of Ni/Mg/g-C₃N₄ composites. The findings provide new insights into the design of cost-effective, thermally stable, and high-performance photocatalysts for visible-light-driven wastewater treatment. Full article

Coordination complexes play a crucial role in modern research. 4-benzopyranone-2-carboxylic acid is a fascinating class of molecules with numerous applications, including the synthesis of pharmaceuticals and valuable chiral compounds. Antibacterial and tuberculostatic medicines, HIV protease inhibitors, intermediates in organic synthesis, and organic catalysis are only a few of the biological applications of chiral complexes. In this study, the synthesis of four metal complexes, C₃₀H₂₈N₂NiO₁₂ [Ni(bzpyr)₂(py)₂(H₂O)₂] (I), C₃₀H₂₄CoN₂O₁₀ [Co(bzpyr)₂(py)₂(H₂O)₂] (II), C₂₀H₂₀O₁₃Zn [Zn(bzpyr)₂(H₂O)₃] (III), and C₃₀H₂₂CuN₂O₉ [Cu(bzpyr)₂(py)₂(H₂O)] (IV), is reported via direct reactions of 4-benzopyranone-2-carboxylic acid with metal salts and pyridine in anhydrous ethanol. Single-crystal X-ray diffraction analysis revealed that complexes I and II crystallize in the chiral space group P-1, whereas III and IV crystallize in the centrosymmetric space group P2₁/c. The structures of these complexes were further characterized by infrared spectroscopy, UV-Visible Diffuse Reflectance Spectroscopy, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, nuclear magnetic resonance, electron paramagnetic resonance spectroscopy and single-crystal X-ray diffraction. In addition, the cytotoxic activities of complexes I–IV were evaluated against the human tumor cell lines K562, A549, HepG2, MDA-MB-231, and SW480, and molecular docking studies were conducted on the four complexes. Full article

This investigation has yielded a remarkably efficient metallic catalyst. Copper (Cu), cobalt (Co), and nickel (Ni) nanoparticles were concurrently deposited onto micron-sized aluminum (µAl) through a displacement reaction, resulting in the formation of [nCu+nCo+nNi]/µAl composites. The interfacial layer of the nanocomposite facilitates the creation of efficient oxygen transport pathways, significantly augmenting thermal release. In the context of the ADN/AP oxidizer, the [nCu+nCo+nNi]/µAl configuration demonstrates a substantial synergistic catalytic effect, reducing its thermal decomposition temperature by an impressive 104.1 °C. Combustion experiments have corroborated that this composite markedly enhances flame intensity, combustion temperature, and the burning rate of the ADN/AP system. The underlying thermal-oxidative mechanism was elucidated through comprehensive thermal analysis of the composite both prior to and following a heat treatment at 1100 °C. Moreover, through an integration of thermal analysis and combustion experiments, the catalytic mechanism of [nCu+nCo+nNi]/µAl on the thermolysis of ADN/AP was elucidated, and a plausible reaction pathway under thermal stimulation was proposed (e.g., ${\mathrm{NH}}_4{\mathrm{ClO}}_4+{{\mathrm{NH}}_4\mathrm{N}({\mathrm{NO}}_2)}_2\stackrel{\mathrm{Cu},\mathrm{Co},\mathrm{Ni}}{\to }{\mathrm{N}}_2+{\mathrm{H}}_2\mathrm{O}+\mathrm{HCl}+{\mathrm{O}}_2+\left[\mathrm{O}\right]$). The developed nanocomposite significantly enhances the performance of oxidizers, presenting considerable potential for a wide array of applications in solid propellants. Full article

The structural, electronic, magnetic, and optical properties are explored in the G-type antiferromagnetic BiFeO₃ system by replacing the Fe cation with transition metals to form the BiFe_0.834X_0.166O₃ compound (where X = Mn, Co, or Ni) by using first-principles DFT+U and TDDFT calculations. All the optimized structures preserve the rhombohedral (R3c) space group, showing moderate changes in the FeO₆ octahedral distortions, lattice parameters, and Fe–O–Fe bond angles. Pristine G-type antiferromagnetic (AFM-G) BiFeO₃ is a typical semiconductor material with a calculated bandgap energy $E_g=1.99$ eV. However, the inclusion of Ni, Co, and Mn at the Fe site introduces additional 3d states near the Fermi level, causing metallic behavior in every case. The local density of states (LDOS), density of states (DOS), and total magnetization results show that the inclusion of Ni, Co, and Mn promotes a transition from antiferromagnetic (AFM) to ferrimagnetic behavior in the modified BiFe_0.834X_0.166O₃ compositions. On the other hand, in the visible spectral region, the time-dependent density functional theory (TDDFT) revealed that the pristine material has refractive index $n\left(\omega \right)$ values between 2.8 and 3.6, showing that the presence of Co and Ni enhances the extinction and absorption coefficients in both visible and ultraviolet regions, whereas the inclusion of Mn produces less significant effects. These results demonstrate that controlled substitution at the Fe site with transition metals simultaneously modifies the structural, electronic, magnetic, and optical properties of the BiFeO₃ system, offering promising potential for applications in electronic devices with multifunctional properties. Full article

Tool steels are critical for high-load applications, e.g., forging and metal-forming, where they face thermal cracking, fatigue, erosion, and wear. This study evaluates the impact of gas nitriding and S-phase PVD coatings on the mechanical and tribological properties of four tool steels: 40CrMnNiMo8-6-4, 60CrMoV18-5, X50CrMoV5-2, and X38CrMoV5-3. Samples were heat-treated (quenched and tempered at 600 °C), then gas-nitrided at 575 °C for 6 h with nitriding potentials (Kn) of 0.18, 0.79, or 2.18, or coated via reactive magnetron sputtering in Ar/N₂ or Ar/N₂/CH₄ atmospheres at 200 °C or 400 °C. Characterization involved XRD, LOM, FE-SEM, GDOES, Vickers hardness (HV0.1), and ball-on-disk wear testing with Al₂O₃_ counter-samples. Gas nitriding produced nitrogen diffusion layers (80–200 μm thick) and compound layers (ε-Fe_(2-3)N, γ’-Fe₄N) at higher Kn, increasing hardness by 80–100% (up to 1100 HV0.1 for steel X38CrMoV5-3). S-phase coatings (1.6–3.6 μm thick) formed expanded austenite with varying N content, achieving comparable hardness (up to 1100 HV0.1) in high-N₂ atmospheres, alongside substrate diffusion layers. Both types of treatment enhance load-bearing capacity, adhesion, and durability, offering superior wear resistance compared to conventional PVD coatings and addressing demands for extended tool life in industrial applications. Full article