Search Results (231)

Owing to the high stability and low cost of nanozymes, they have been extensively investigated and reported. In this work, highly active CeO₂ nanoflowers were first prepared and then different metal elements were doped into the CeO₂ nanoflower matrix via a novel synthesis method to fabricate M-CeO₂ (M = Cu, Fe, Co, Mn, La) nanomaterials. Mn-CeO₂ with the highest peroxidase-like activity was selected via systematic screening, the as-prepared Mn-CeO₂ nanocomposites exhibited enhanced enzyme-like activity due to the strong metal-support interaction. This article explored the effects of doping ratio, pH, temperature, reaction time, and material concentration on its activity. A simple sensitive and selective colorimetric method was established and successfully used to detect hydrogen peroxide and ascorbic acid sensitively. When the hydrogen peroxide (H₂O₂) concentration is within the 2.0–120.0 μM range, the UV-visible absorbance at 652 nm was associated linearly with the H₂O₂ concentration, R² = 0.9959, LOD = 1.7 μM (S/N = 3). The absorbance of the reaction system showed a good linear relationship with the ascorbic acid (AA) concentration (1.0–40.0 μM, R² = 0.992), LOD = 0.98 μM (S/N = 3). This study provides an effective way to construct efficient nanozymes and their potential applications in sensing and detection. Full article

Both Co-free and lithium- and manganese-rich layered oxide Li(Li_0.2Mn_xNi_yFe_z)O₂ (MNF) cathodes have recently attracted attention in lithium-ion battery (LIB) research due to their high capacities of over 250 mAhg⁻¹, as well as being more eco-friendly and inexpensive than commercial NMC and LiCoO₂. However, they still suffer from lower experimental capacity as well as capacity decay, voltage fade, poor rate capability, and thermal instability. In this paper, fluorine (F)-doped Li_1.2(Mn_0.5Ni_0.2Fe_0.1)O_2(1−x)F_2x (MNF502010, x = 0, 0.025, 0.05, 0.075, 0.1) cathode materials have been synthesized in the nanoscale via sol–gel and subsequent solid-phase calcination to address some of these problems. The resulting 5% F-doped MNF502010 cathode demonstrates the advantage of fluorine doping, which makes a significant contribution to the formation of a well-ordered layer structure with a minimal LiM₂O₄ spinel phase as an impurity. This composition achieves an initial discharge capacity of 252 mAhg⁻¹ (1C = 250 mAhg⁻¹) and a 156 mAhg⁻¹ discharge capacity at 0.3 C on the 100th discharge, with an average voltage fade of 0.24 V. The optimization of fluorine composition results in an enhancement in the activation of the Li₂MnO₃-type monoclinic phase, as well as an increase in the electronic conductivity compared to the fluorine-free cathode. To understand the structural origin of this improved performance, X-ray absorption spectroscopy (XAS) measurements were carried out on pristine and cycled MNF electrodes. Full article

The high energy consumption of lead anodes in zinc production is caused by the slow oxygen evolution reaction (OER). We made a La-Mn co-doped β-PbO₂ anode using electrodeposition to solve this issue. The XRD and XPS results show that adding La shrinks the lattice and changes the electron structure. This helps Mn⁴⁺ change into active Mn³⁺ and creates more active oxygen on the surface, making the reaction easier. EIS tests show that the charge transfer resistance (R_ct) decreased by 4.2 times, decreasing from 147.6 Ω to 34.72 Ω at 1.0 V. The Bode phase peak also moved to a lower frequency (from 122 Hz to 0.215 Hz), proving that the electrochemically active surface area (ECSA) increased significantly. At the industrial current of 50 mA cm⁻², the anode shows a low overpotential of 840 mV and a Tafel slope of 265 mV dec⁻¹. This improved performance saves 187.10 kWh of energy per ton of zinc. Therefore, the LaMn-β-PbO₂ anode is a promising and energy-saving option for industrial zinc production. Full article

The development of efficient spinel oxide catalysts for low-temperature oxidation of volatile organic compounds (VOCs) remains an important research objective. In this work, Ru was doped into a CoMn₂O₄ spinel to enhance its catalytic activity toward toluene oxidation and the underlying promotion mechanism of Ru doping was systematically investigated. The resulting Ru-CoMn₂O₄ catalyst showed remarkable performance, with T₉₀ reaching approximately 224 °C at a WHSV of 60,000 cm³ g⁻¹ h⁻¹ and nearly 100% CO₂ selectivity above 200 °C. Mechanism studies revealed that the reaction followed both Mars–van Krevelen (MvK) and Eley–Rideal (E–R) pathways. The reaction rates were strongly influenced by the oxidizing capacity of the catalyst, the abundance of highly valent surface species (namely Co³⁺, Mn⁴⁺, and Ru⁴⁺), adsorbed toluene, lattice oxygen, gaseous toluene, and adsorbed oxygen. With Ru doping, new Ru–O–Mn and Ru–O–Co chains formed in the CoMn₂O₄ spinel structure, leading to a moderate enhancement in oxidizing ability and a moderate increase in the concentration of highly valent surface species, adsorbed toluene, and lattice oxygen. Although a slight reduction in adsorbed oxygen was observed, Ru doping significantly boosted the overall toluene oxidation activity of CoMn₂O₄. In summary, Ru-CoMn₂O₄ represented a promising catalyst for the efficient oxidation of VOCs. Full article

Transition metal (TM)-doped zinc oxide (ZnO) and zirconium dioxide (ZrO₂) nanocrystals exhibit complex correlations between crystal structure, defect chemistry, vibrational properties, and magnetic behavior that are strongly governed by synthesis route and dopant incorporation mechanisms. This review critically summarizes recent progress on Fe-, Mn-, and Co-doped ZnO and ZrO₂ nanocrystals synthesized by wet chemical, hydrothermal, and microwave-assisted hydrothermal methods, with emphasis on synthesis-driven phase evolution and apparent solubility limits. ZnO and ZrO₂ are treated as complementary host lattices: ZnO is a semiconducting, piezoelectric oxide with narrow solubility limits for most 3d dopants, while ZrO₂ is a dielectric, polymorphic oxide in which transition metal doping may stabilize tetragonal or cubic phases. Structural and microstructural studies using X-ray diffraction, electron microscopy, Raman spectroscopy, and Mössbauer spectroscopy demonstrate that at low dopant concentrations, TM ions may be partially incorporated into the host lattice, giving rise to diluted or defect-mediated magnetic behavior. When solubility limits are exceeded, nanoscopic secondary oxide phases emerge, leading to superparamagnetic, ferrimagnetic, or spin-glass-like responses. Magnetic measurements, including DC magnetization and AC susceptibility, reveal a continuous evolution from paramagnetism in lightly doped samples to dynamic magnetic states characteristic of nanoscale magnetic entities. Vibrational spectroscopy highlights phonon confinement, surface optical phonons, and disorder-activated modes that sensitively reflect nanocrystal size, lattice strain, and defect populations, and often correlate with magnetic dynamics. Rather than classifying these materials as diluted magnetic semiconductors, this review adopts a synthesis-driven and correlation-based framework that links dopant incorporation, local structural disorder, vibrational fingerprints, and magnetic response. By emphasizing multi-technique characterization strategies required to distinguish intrinsic from extrinsic magnetic contributions, this review provides practical guidelines for interpreting magnetism in TM-doped oxide nanocrystals and outlines implications for applications in photocatalysis, sensing, biomedicine, and electromagnetic interference (EMI) shielding. Full article

Layered transition-metal oxides are among the most promising sodium-ion battery cathodes owing to their high specific capacities and structurally tunable frameworks. However, the prototypical P2-Na_0.67Ni_0.33Mn_0.67O₂ (NM) undergoes an irreversible P2 → O2 phase transition at high voltages, accompanied by severe lattice strain and capacity fade, which hinders practical deployment. Here, we propose a cooperative regulation strategy that couples Zn/Al co-doping with Na enrichment, and successfully synthesize P2-Na_0.80Ni_0.14Zn_0.14Mn_0.58Al_0.14O₂ (NMZA-N14). The optimized NMZA-N14 delivers an initial discharge capacity of 125 mAh g⁻¹ at 0.1C and demonstrates exceptional cycling and rate performance, retaining 98.6% of its capacity after 100 cycles at 0.2C and 93.6% after 200 cycles at 1C. Kinetic analyses indicate a higher Na⁺ diffusion coefficient and a lower charge-transfer resistance in NMZA-N14, evidencing substantially accelerated ion transport. In situ X-ray diffraction further reveals a reversible P2 → OP4 phase transition in the high-voltage regime with a unit-cell volume change of only ~2.27%, thereby avoiding the irreversible structural degradation observed in NM. This synergistic modulation markedly enhances structural stability and electrochemical kinetics, providing a viable pathway for the rational design of high-performance sodium-ion battery cathodes. Full article

The development of highly active, thermally stable, and low-CO-selective catalysts is critical for practical methanol steam reforming (MSR) to produce high-purity hydrogen for fuel cell applications. In this work, a series of Mn–Cu/Al₂O_x catalysts with varying Mn/Cu/Al molar ratios were synthesized via co-precipitation and systematically investigated to establish the relationship between composition, structure, and catalytic performance. XRD analysis revealed the formation of spinel-type CuAl₂O₄ and MnAl₂O₄ phases, with Mn preferentially occupying octahedral B-sites to form MnAl₂O₄, thereby inducing lattice distortion and inhibiting grain growth. SEM and TEM–EDS mapping confirmed uniform elemental distribution and a porous nanoscale morphology, while H₂-TPR results suggested that increasing the Mn/Cu ratio strengthens Mn–Cu interactions, shifts Cu²⁺ reduction to higher temperatures, and enhances Cu dispersion (up to 26.11 m²/g). XPS analysis indicated that Mn doping enriches Mn³⁺ species and facilitates oxygen vacancy formation, which promotes water–gas shift (WGS) activity and suppresses CO formation. Catalytic testing (240–300 °C) showed that Mn₂Cu₂Al₄O_x achieved the highest methanol conversion while maintaining low CO selectivity; in contrast, reducing the Mn/Cu ratio increased CO selectivity, detrimental to hydrogen purification. Stability tests under continuous steam exposure for 24 h demonstrated minimal activity loss (~2%) and negligible increase in CO selectivity (<1%), confirming excellent hydrothermal stability. The results indicate that tailoring the Mn/Cu ratio optimizes the balance between redox properties and metallic Cu dispersion, offering a promising route to design low-CO, durable catalysts for on-site hydrogen generation via MSR. Full article

Copper (Cu) doping is recognized as an effective strategy to enhance the electrochemical properties of LiNi_1−x−yCo_xMn_yO₂ (NCM) cathode materials. However, the influence of Cu²⁺ doping on particle size and grain boundary fusion remains insufficiently explored. A simple microwave-assisted solution combustion synthesis method was used to introduce Cu²⁺ into LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523), aiming to regulate particle size and grain boundary fusion. The results demonstrate that increasing the Cu²⁺ doping content promotes particle growth, while an appropriate doping level reduces the degree of grain boundary fusion and cation mixing. Benefiting from these structural improvements, the optimized LiNi_0.5Co_0.2Mn_0.29Cu_0.01O₂ (Cu–1) cathode exhibits significantly enhanced electrochemical performance, delivering a discharge capacity of 128.6 mAh g⁻¹ after 100 cycles at 0.2 C, which is 32 mAh g⁻¹ higher than value of the undoped sample (96.6 mAh g⁻¹). These findings underscore that tailored Cu²⁺ doping can effectively optimize the microstructure of NCM523, leading to superior cycling stability, and provide new insights into the design of high-performance NCM cathodes. Full article

Element doping technology is widely recognized as an effective strategy for high-performance MnO₂-based cathode materials. While this approach improves the electronic and ionic conductivity of MnO₂, it is often accompanied by the introduction of oxygen vacancies. This synergistic effect poses challenges for precisely investigating the effect of doping elements on the d-electron configuration of the Mn site and establishing atomic-level structure-activity relationships for high-energy aqueous zinc-MnO₂ batteries. In this paper, the rational design of d-electron configurations in the Mn site has been achieved through simple Co doping in α-MnO₂ (CMO). Experimental results confirm that the introduction of Co can delocalize the d-electrons of the Mn site and increase the ratio of e_g (d_z² and d_x²_−y²) occupancy. Consequently, the charge transfer resistance, electrode polarization, and Zn²⁺ diffusion coefficient of the CMO-2 cathode have been greatly optimized. Thus, the as-prepared electrode delivers a high specific capacity of 287.4 mAh g⁻¹ at 1 A g⁻¹, with a capacity retention rate of 92.8% and a corresponding remaining capacity of 199.7 mAh g⁻¹ after 700 cycles. This study paves the road for the designation and construction of high-energy MnO₂ cathodes with optimized electronic structures for advanced aqueous zinc ion batteries. Full article

The photocatalytic degradation of Crystal Violet (CV) using ZnO-based nanomaterials presents a promising solution for addressing water pollution caused by synthetic dyes. This review highlights the exceptional efficiency of ZnO and its modified forms—such as doped, composite, and heterostructured variants—in degrading CV under both ultraviolet (UV) and solar irradiation. Key advancements include strategic bandgap engineering through doping (e.g., Cd, Mn, Co), innovative heterojunction designs (e.g., n-ZnO/p-Cu₂O, g-C₃N₄/ZnO), and composite formations with graphene oxide, which collectively enhance visible-light absorption and minimize charge recombination. The degradation mechanism, primarily driven by hydroxyl and superoxide radicals, leads to the complete mineralization of CV into non-toxic byproducts. Furthermore, this review emphasizes the emerging role of Artificial Neural Networks (ANNs) as superior tools for optimizing degradation parameters, demonstrating higher predictive accuracy and scalability compared to traditional methods like Response Surface Methodology (RSM). Potential operational challenges and future directions—including machine learning-driven optimization, real-effluent testing potential, and the development of solar-active catalysts—are further discussed. This work not only consolidates recent breakthroughs in ZnO-based photocatalysis but also provides a forward-looking perspective on sustainable wastewater treatment strategies. Full article

Confronted with increasing global food demands, diminishing arable land, and climate volatility, controlled-environment agriculture with advanced red and far-red LED lighting can enhance photosynthesis and optimize plant growth. This investigation reports the generation of a Mn⁴⁺/Nd³⁺ co-doped Y₂SiO₅ phosphor with a Nd³⁺ concentration ranging from 0.1 to 2.5 mol% via a solid-state synthesis method, aiming to enhance red and far-red emission for plant cultivation LEDs. For the Y₂SiO₅:Mn⁴⁺ (1 mol%), Nd³⁺ (2 mol%) phosphor, the phase integrity, nanostructured morphology, elemental mapping, and vibrational characteristics were examined using XRD, Rietveld analysis, FTIR, SEM, and EDX. Nd³⁺ ions act as near-infrared excitation mediators, ensuring efficient Nd³⁺ → Mn⁴⁺ energy transfer upon 808 nm excitation, and this leads to pronounced red photoluminescence from Mn⁴⁺ ions that covers the range of 640–710 nm, exhibiting strong emission peaks centered at 650nm, 663nm, and 685nm, coinciding with the absorption band of phytochromes and chlorophyll. The optimal emission intensity was accomplished for a Nd³⁺ doping concentration of 2 mol%, beyond which concentration quenching occurred. The material produced a strong, concentrated deep red emission with CIE coordinates near (0.73, 0.27) and a high color purity of 98.96%, making it well-suited for photosynthetic activation. A phosphor-integrated red pc-LED was fabricated, and Tulsi plants were grown under this LED during the winter in Meghalaya, a period critical for plant growth due to the low ambient light. Over a 30-day period, the plants exhibited enhanced height and leaf development, demonstrating the practical potential of Mn⁴⁺/Nd³⁺ co-doped Y₂SiO₅ for energy-efficient, wavelength-optimized horticultural lighting. Full article

Rechargeable aqueous Zn-MnO₂ batteries are positioned as a highly promising candidate for next-generation energy storage, owing to their compelling combination of economic viability, inherent safety, exceptional capacity (with a theoretical value of ≈308 mAh·g⁻¹), and eco-sustainability. However, this system still faces multiple critical challenges that hinder its practical application, primarily including the ambiguous energy storage reaction mechanism (e.g., unresolved debates on core issues such as ion transport pathways and phase transition kinetics), dendrite growth and side reactions (e.g., the hydrogen evolution reaction and corrosion reaction) on the metallic Zn anode, inadequate intrinsic electrical conductivity of MnO₂ cathodes (≈10⁻⁵ S·cm⁻¹), active material dissolution, and structural collapse. This review begins by systematically summarizing the prevailing theoretical models that describe the energy storage reactions in Zn-Mn batteries, categorizing them into the Zn²⁺ insertion/extraction model, the conversion reaction involving MnO_x dissolution–deposition, and the hybrid mechanism of H⁺/Zn²⁺ co-intercalation. Subsequently, we present a comprehensive discussion on Zn anode protection strategies, such as surface protective layer construction, 3D structure design, and electrolyte additive regulation. Furthermore, we focus on analyzing the performance optimization strategies for MnO₂ cathodes, covering key pathways including metal ion doping (e.g., introduction of heteroions such as Al³⁺ and Ni²⁺), defect engineering (oxygen vacancy/cation vacancy regulation), structural topology optimization (layered/tunnel-type structure design), and composite modification with high-conductivity substrates (e.g., carbon nanotubes and graphene). Therefore, this review aims to establish a theoretical foundation and offer practical guidance for advancing both fundamental research and practical engineering of Zn-manganese oxide secondary batteries. Full article

All-solid-state lithium batteries (ASSLBs) employing Li-rich layered oxide (LLO) cathodes are regarded as promising next-generation energy storage systems owing to their outstanding energy density and intrinsic safety. Polymer-in-salt solid electrolytes (PISSEs) offer advantages such as high room-temperature ionic conductivity, enhanced Li anode interfacial compatibility, and low processing costs; however, their practical deployment is hindered by poor oxidative stability especially under high-voltage conditions. In this study, we report the rational design of a bilayer electrolyte architecture featuring an in situ solidified LiClO₄-doped succinonitrile (LiClO₄–SN) plastic–crystal interlayer between a Li_1.2Mn_0.6Ni_0.2O₂ (LMNO) cathode and a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based PISSE. This PISSE/SN–LiClO₄ configuration exhibits a wide electrochemical stability window up to 4.7 V vs. Li⁺/Li and delivers a high ionic conductivity of 5.68 × 10⁻⁴ S cm⁻¹ at 25 °C. The solidified LiClO₄-SN layer serves as an effective physical barrier, shielding the PVDF-HFP matrix from direct interfacial contact with LMNO and thereby suppressing its oxidative decomposition at elevated potentials. As a result, the bilayer polymer-based cells with the LMNO cathode demonstrate an initial discharge capacity of ∼206 mAh g⁻¹ at 0.05 C and exhibit good cycling stability with 85.7% capacity retention after 100 cycles at 0.5 C under a high cut-off voltage of 4.6 V. This work not only provides a promising strategy to enhance the compatibility of PVDF-HFP-based electrolytes with high-voltage cathodes through the facile in situ solidification of plastic interlayers but also promotes the application of LMNO cathode material in high-energy ASSLBs. Full article

Prussian blue (PB) and its analogs (PBAs) are considered ideal cathode materials for sodium-ion batteries (SIBs) due to the following merits, including high redox potential, simple synthesis methods, and excellent structural stability. Herein, we synthesized a high-entropy PB cathode material, Na_1.20Mn_0.38Fe_0.15Ni_0.14Co_0.15Cu_0.16[Fe(CN)₆]_0.82□_0.18·0.38H₂O (HE-HCF), through a facile co-precipitation method. The five transition metals in HE-HCF have similar atomic sizes and electronegativity, collectively occupying the high-spin Fe-HS sites. The manganese-based system design reduces the preparation cost, and the high-entropy doping approach further decreases the content of crystalline water in the structure. Benefiting from the synergistic effects of the multiple component elements, HE-HCF demonstrates a capacity retention rate of 72.7% at 0.1 A g⁻¹. Moreover, it even maintains 85.3% of its initial capacity after 1000 cycles at 1 A g⁻¹. Electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) analyses further confirm that HE-HCF exhibits low charge transfer resistance and a small reaction activation energy. Full article

Spintronics, an interdisciplinary field merging magnetism and electronics, has attracted considerable interest due to its potential to transform data storage, logic devices, and emerging quantum technologies. Among the materials explored for spintronic applications, metal oxide nanostructures synthesized via sol–gel methods offer a unique combination of low-cost processing, structural tunability, and defect-mediated magnetic control. This comprehensive review presents a critical overview of recent advances in sol–gel-derived magnetic oxides, such as Co-doped ZnO, La_1−xSr_xMnO₃, Fe₃O₄, NiFe₂O₄, and transition-metal-doped TiO₂, with emphasis on synthesis strategies, the dopant distribution, and room-temperature ferromagnetic behavior. Key spintronic functionalities, including magnetoresistance, spin polarization, and magnetodielectric effects, are systematically examined. Importantly, this review differentiates itself from the prior literature by explicitly connecting sol–gel chemistry parameters to spin-dependent properties and by offering a comparative analysis of multiple oxide systems. Critical challenges such as phase purity, reproducibility, and defect control are also addressed. This paper concludes by outlining future research directions, including green synthesis, the integration with 2D materials, and machine-learning-assisted optimization. Overall, this work bridges sol–gel synthesis and spintronic material design, offering a roadmap for advancing next-generation oxide-based spintronic devices. Full article