Search Results (2,241)

Metal oxide nanoparticles serve as crucial drivers in modern biomedical, catalytic, environmental, and energy technologies due to their high surface-to-volume ratios and quantum confinement properties. Traditional chemical and physical synthesis methods remain limited by significant energy footprints, high costs, and the use of hazardous reagents. To address these challenges, bioinspired (“green”) synthesis has emerged as a sustainable paradigm that employs biological systems as nature nanofactories. This critical review provides a provides a comprehensive and systematic analysis of the green synthesis of major metal oxide systems (ZnO, TiO₂, Fe₃O₄/Fe₂O₃, CuO, Co₃O₄, CeO_2, and MnO₂) using diverse biological templates, including plant extracts, bacteria, fungi, algae, and biopolymers. Moving beyond simple descriptive summaries, we critically evaluate the foundational electron-transfer and nucleation mechanism, systematically correlate processing parameters with physical outcomes, and offer a rigorous comparative analysis across different biological kingdoms. Finally, we directly address the underlying challenges facing the field: reproducibility bottlenecks, scalability limits, environmental safety variations, and regulatory hurdles necessary for industrial translation. Full article

Radiation therapy is widely used for cancer treatment. To improve therapeutic efficacy, traditional radiosensitizers are often used in combination. However, their toxic side effects necessitate urgent development of safer alternative biogenic radiosensitizers. Herein, a green approach was used to synthesise ZnO NPs, CuO NPs, and ZnO-CuO NCs using S. africana Luteus, and their ability to enhance the radiosensitizing effect of proton irradiation on Michigan Cancer Foundation-7 (MCF7) breast cancer cell line was evaluated. The biogenic nanoparticles are characterised in detail through several analytical techniques, including Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscopy (SEM). Interestingly, the NPs showed concentration-dependent effects on MCF7 viability, with CuO NPs exhibiting the strongest effect (IC₅₀ = 42.90 µg/mL), followed by ZnO-CuO NCs (71.12 µg/mL) and ZnO NPs (103.43 µg/mL). Proton irradiation produced a dose-dependent decrease in clonogenic survival of MCF7 cells, and ZnO-CuO NCs displayed the highest enhancement of proton-induced cell death, with a Dose Enhancement Factor (DEF) of 1.69, compared with CuO NPs (1.46) and ZnO NPs (1.09). Holotomographic microscopy (HTM) data further confirmed that ZnO-CuO NCs impaired cellular macromolecules more than the individual NPs. Findings from this study suggest that the biogenic NPs are promising radiosensitizers for cancer radiotherapy. Full article

CoCrFeNi-based high-entropy alloys (HEAs) have shown great potential for widespread applications in aerospace, chemical, and medical equipment fields due to their high strength, wear resistance, corrosion resistance, and thermal stability. In the present study, a series of Ni₂CoCrFeV_xCu_y alloys were designed to obtain a ductile FCC matrix suitable for ceramic-particle reinforcement. Subsequently, two representative reinforcement strategies, namely, in situ TiC formation and direct TiN nanoparticle addition, were employed to investigate their effects on the microstructure and mechanical properties of the alloy. The results showed that Ni₂CoCrFeV_0.5Cu_0.2 exhibited the best strength–ductility balance, with a tensile elongation of 51.8% among the designed alloys. Besides, the comprehensive performance of high-entropy alloys can be effectively enhanced by in situ generation of TiC and addition of TiN particles. The in situ synthesized TiC exhibited a finer and more uniform distribution than the directly added TiN particles, resulting in a more favorable strength–ductility balance under the present processing conditions. Full article

This study investigates the potential of xylan acetylated using imidazolium-based ionic liquids, particularly 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), as a functional matrix for ZnO and CuO nanoparticles (ZnO NPs and CuO NPs) in composite coatings for food packaging paper. A single coating layer (approximately 5 g/m²) was applied on both sides of the paper samples to improve barrier properties against water, oils, fats, and microbial contamination. The obtained results show that the combination of acetylated xylan with ZnO and CuO nanoparticles improved surface hydrophobicity, with contact angle values reaching 83° and 97°, respectively. The coatings exhibited antibacterial activity against Bacillus sp., as well as a reduction in fungal development of Penicillium spp., as evidenced by the observed inhibition of conidia sporulation. These findings indicate that ionic liquid-assisted acetylation of xylan using [Emim]Ac is an effective route for chemical modification of hemicelluloses. The developed xylan-based coatings demonstrate promising functional properties for potential application in sustainable food packaging materials, within the scope of the performed experiments. Full article

Copper cobalt sulfide (Cu-CoS₂) nanoparticles (NPs) were synthesized via the co-precipitation method in the present study. The synthesized nanoparticles were employed as photocatalysts for the degradation of two hazardous dyes, Eosin B (EB) and Rhodamine B (RB), under sunlight irradiation. The synthesized nanoparticles were characterized using Energy Dispersive X-ray spectroscopy, Scanning Electron Microscopy, UV-Visible spectroscopy, Fourier Transform Infrared spectroscopy, and X-ray Diffraction analysis. The calculated optical band gap of Cu-CoS₂ was 2.06 eV, while the point of zero charge (PZC) was determined to be 7. The XRD results confirmed the crystalline nature of the Cu-CoS₂ nanoparticles with an average crystallite size of 28.23 nm. The catalyst exhibited higher photocatalytic degradation efficiency for EB than for RB in single-dye solutions. In contrast, the presence of EB in the binary dye mixture did not significantly influence the degradation of RB. The effects of various operational parameters, including dye concentration, pH, temperature, and catalyst dosage, were systematically investigated. The photocatalytic degradation efficiency of both dyes decreased with increasing initial dye concentration. Optimum degradation conditions for both single and binary dye systems were obtained at dye concentrations of 40:20 μM, pH 5 for EB, pH 9 for RB, and a temperature of 50 °C. The maximum degradation efficiencies achieved in single-dye solutions were 97% for RB and 92% for EB, whereas degradation efficiencies of 98% for RB and 82% for EB were observed in binary dye systems. Furthermore, first-order and second-order kinetic models were applied to evaluate the photodegradation process, and the experimental data showed better agreement with the second-order kinetic model. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

The development of low-cost and highly sensitive electrochemical sensing platforms for pesticide monitoring has attracted significant attention in recent years. In this study, coke-derived carbon (CDC) was successfully synthesized from petroleum coke through high-temperature carbonization under a nitrogen atmosphere. Subsequently, a CDC@CuO-NP nanocomposite was fabricated by depositing copper oxide nanoparticles onto the CDC matrix. The morphology, structure, and elemental composition of the synthesized materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and elemental mapping analyses, confirming the successful formation of the composite and the uniform distribution of CuO nanostructures on the carbon surface. Electrochemical characterization demonstrated that the incorporation of CuO significantly enhanced the electrochemical performance of CDC by increasing the electroactive surface area and facilitating electron transfer. The CDC@CuO-NP-modified glassy carbon electrode was applied for the electrochemical detection of dichlorvos (DDVP) using electrochemical impedance spectroscopy (EIS). The sensor exhibited a concentration-dependent increase in charge-transfer resistance and showed a linear response in the concentration range of 247–3770 nM, with the regression equation y = 47.1458C + 111.8162 and a correlation coefficient of R² = 0.9832. The developed sensor achieved a low limit of detection (LOD) of 2.3 nM, demonstrating high sensitivity toward DDVP. These results indicate that the CDC@CuO-NP nanocomposite is a promising, low-cost, and efficient electrode material for the sensitive determination of organophosphorus pesticides and has considerable potential for environmental monitoring and food safety applications. Full article

The nucleation and growth mechanisms of copper electrodeposition from Cu(I)-containing-reline, a deep eutectic solvent, were investigated through a combination of electrochemical techniques and surface characterization. Cyclic voltammetry revealed the characteristic nucleation loop associated with an overpotential-driven electrocrystallization process, from which the equilibrium potential of the Cu(I)/Cu(0) redox couple was determined to be −0.35 V vs. a Ag quasi-reference electrode. Experimental potentiostatic current density transients were analyzed using nucleation models capable of accounting for both adsorption and three-dimensional (3D) diffusion-controlled growth, thereby allowing deconvolution of the individual contributions to the overall current response. The kinetic parameters, including the nucleation frequency and the number density of active sites, exhibited an exponential dependence on the applied overpotential, thus indicating enhanced nucleation kinetics at greater driving forces, while determining a Cu(I) diffusion coefficient of (3.39 + 0.09) × 10⁻⁷ cm² s⁻¹. Thermodynamic analysis showed that the Gibbs free energy of the formation of the critical nucleus decreases with increasing overpotential and follows the expected dependence on the inverse square of the overpotential, in agreement with classical nucleation theory. The estimated critical nucleus size was found to be smaller than one atom, suggesting that nucleation occurs at highly active surface sites. Furthermore, an exchange current density of (3 ± 1) μA cm⁻² was estimated for the Cu(I) electrochemical reduction. Scanning electron microscopy revealed a high density of copper nanoparticles (~20 nm) distributed across the electrode surface, along with larger aggregates (~100 nm) formed by coalescence and growth, consistent with a progressive nucleation mechanism. X-ray photoelectron spectroscopy confirmed that the deposits consist exclusively of metallic copper, with no evidence of oxidized species. These results demonstrate that copper electrodeposition in reline is governed by a complex interplay between the thermodynamic driving force, the interfacial kinetics, and mass transport, comprehensively providing fundamental insight into the electrocrystallization processes in deep eutectic solvents. Full article

This study experimentally investigates the mixed convection heat transfer performance of CuZnFe₂O₄–water-based magnetic nanofluids in a cylindrical minichannel under the influence of external magnetic fields. Nanofluids with three different volumetric concentrations (0.25%, 0.50%, and 0.75%) were synthesized and characterized in terms of thermophysical properties. The experiments were conducted within the Richardson number range of 0.1–10 to ensure mixed convection conditions, while magnetic field intensities of 220 G, 300 G, and 380 G were applied using custom-built electromagnets. Results show that suspending CuZnFe₂O₄ nanoparticles significantly enhances the heat transfer rate compared to pure water, mainly due to increased thermal conductivity and particle–fluid interactions. The application of a magnetic field further augments the Nusselt number by disturbing the thermal boundary layer and intensifying particle motion, leading to up to 64.4% improvement compared with pure water at similar Reynolds numbers. In addition, Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) were employed to determine the most influential parameters on heat transfer performance and to develop a predictive correlation for the Nusselt number as a function of Reynolds number, nanoparticle concentration, and magnetic field intensity. The findings highlight the combined effects of nanoparticle suspension and magnetic field application as a promising approach for enhancing heat transfer in low-flow mixed convection regimes, offering valuable insights for thermal management in miniaturized cooling systems. Full article

Monometallic nanoparticles tend to aggregate and exhibit limited catalytic performance, rendering them inadequate for high-efficiency electrocatalytic applications. In this study, a green and mild liquid-phase reduction method was employed, using sodium borohydride to simultaneously reduce graphene oxide (GO) and metal precursors. This approach enabled the uniform and highly dispersed loading of silver–copper bimetallic alloy nanoparticles (Ag_1−xCu_x NPs) onto the surface of reduced graphene oxide (RGO). By tuning the Ag/Cu molar ratio, the size, composition, and morphology of the nanoparticles were precisely controlled. Characterization by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed that GO was efficiently reduced to RGO, and the bimetallic nanoparticles were uniformly distributed on the RGO surface in an alloy state with small particle size and no obvious agglomeration. A strong interfacial interaction between the metal nanoparticles and the support was also observed. Electrochemical tests demonstrated that the composite exhibits excellent electrocatalytic activity toward the reduction of H₂O₂. Notably, the reduction peak current at the Ag_0.5Cu_0.5NPs/RGO modified electrode was 1.8 and 2.3 times higher than those at the monometallic Ag/RGO and Cu/RGO electrodes, respectively. These results provide a reliable theoretical basis and a viable research route for the controllable synthesis of low-cost, high-performance electrocatalytic nanocomposites and their application in electrochemical H₂O₂ sensing. Full article

Gadolinium is a rare-earth element that is promising for the field of biomedicine due to its unique properties that enhance image quality, giving it high potential in targeted cancer therapy, antimicrobial treatments, etc. The disadvantage of Gd-containing materials is their high toxicity. In this work, ensembles of Fe and Al₂O₃ nanoparticles were fabricated by the electric explosion of wire and Gd ribbons using rapid quenching techniques. Stable Fe, Fe/Gd and Fe/Gd/Al₂O₃ aqueous suspensions with a Z-potential of about −54 mV were fabricated by the ball-milling mechanosynthesis of Fe (100%), Fe and Gd (70 and 30 wt. % accordingly) and Fe, Al₂O_3, and Gd (69, 30 and 1 wt.% accordingly). Fillers from suspensions were used for the synthesis of epoxy composites mimicking natural tissue with embedded magnetic particles. The concentration range for synthesized epoxy composites (0, 5, 10, and 15 wt.% of the filler) corresponded to the biomedical range of interest. Thin-film magnetoimpedance (MI) elements were prepared by a sputtering technique: conventional [FeNi/Cu]₅/Cu/[Cu/FeNi]₅ (NP) element and [FeNi/Cu]₅/Cu/[Cu/P{FeNi]₅} element with patterned top multilayer (SqP). They showed a maximum MI ratio of about 160% for NP and about 60% for SqP. MI sensor response was affected by the presence of filled magnetic composites in the shape of cylinders (5 mm × 4 mm) situated at about 1 mm due to the stray fields in the filler. MI response showed a linear dependence on the filler concentration for each selected position. These results open the possibility to develop new iron- and gadolinium-containing materials for simultaneous magnetic imaging and detection by magnetic field sensors, extending the functional properties of Fe/Gd materials for biomedical devices and therapies. Full article

This study reports the plant-mediated synthesis of copper-oxide-decorated magnetic iron oxide composite (CuO@Fe₃O₄) nanoparticles using Dolomiaea costus extract and their application as nanocarriers for β-galactosidase immobilization. The fabricated nanocomposite exhibited favorable physicochemical properties, achieving an immobilization efficiency of 83%, with enhanced thermal and pH tolerance compared to the free enzyme. Kinetic analysis revealed a modest increase in Km and a 31% decrease in Vmax after immobilization, while maintaining 69% of the catalytic activity, confirming the system’s suitability for industrial lactose hydrolysis. Reusability and storage tests showed 79% retained activity after five cycles and 77% after 60 days at 4 °C. In milk hydrolysis, the immobilized enzyme achieved 77% conversion within 3 h, following pseudo-first-order kinetics. Biocompatibility was evaluated using HepG2 cells via the MTT assay. BDH, MDH, and ABC maintained high cell viability across the tested dilution range of 25–100% (v/v), indicating no detectable cytotoxic effect under the experimental conditions, whereas cisplatin showed marked cytotoxicity with an IC₅₀ of 14.98 µg/mL. These findings demonstrate that the green-synthesized CuO@Fe₃O₄ support provides a safe, reusable, and magnetically recoverable platform for β-galactosidase immobilization, offering a promising sustainable strategy for producing lactose-free dairy products. Full article

Hydrogen sulfide (H₂S) is a contaminant for water quality, which can affect the eyes, respiratory system, and central nervous system, and may also cause damage to multiple organs such as the heart. Therefore, rapid and sensitive detection of trace H₂S is of great importance. In this work, a novel gold nanoparticle/2D porphyrin metal–organic framework nanocomposite (Au NPs/2D Cu-TCPP MOF) was prepared, and a novel electrochemical sensing method was established for the rapid determination of H₂S by differential pulse voltammetry (DPV). In 0.1 M PBS (pH 7.0), the detection limit of H₂S is as low as 0.03 μM, the linear range is 0.1–10 μM, and the response time is about 7 s. In addition, this method exhibits good stability and reproducibility, which can be applied to the rapid detection of H₂S in mine water samples. This study provides a reference for the development of new detection methods for H₂S in various complex environments. Full article

To address the urgent demand for eco-friendly and low-cost catalysts to replace toxic heavy-metal additives in energetic materials, this work focuses on developing biomass-derived copper-doped porous carbon (CuPC) as a high-efficiency catalyst for the thermal decomposition and combustion of molecular perovskite energetic material (H₂dabco)NH₄(ClO₄)₃(DAP-4). Biomass carbonaceous material has garnered extensive attention in many fields, owing to the low cost, high utilization efficiency, and environment protection. Herein, the CuPC catalysts were rationally designed and fabricated via the high-temperature carbonization treatment of biomass carbonaceous material precursor. The catalytic effects of CuPC on the thermal decomposition and combustion characteristics of DAP-4 were systematically investigated. The results revealed that CuPC possessed inherent catalysis property on the decomposition and combustion reaction of DAP-4. Cu_xO_y nanoparticles were uniformly distributed on the surface of carbonized biomass substrates, endowing the catalysts with superior dispersibility. Thermal analysis results indicated that the addition of 5 wt% CuPC-3 reduced the thermal decomposition peak temperature from 378 °C of raw DAP-4 to 350 °C of DAP-4/CuPC-3. Moreover, the apparent activation energy of DAP-4 was notably decreased with the incorporation of CuPC catalysts. The combustion characterization results demonstrated that DAP-4 exhibited a more intense combustion process with the addition of CuPC, accompanied by elevated maximum combustion temperature and enhanced combustion heat. The catalytic mechanism of CuPC on the thermal decomposition and combustion of DAP-4 was further proposed. This work provides a targeted strategy for designing sustainable biomass-based catalysts to optimize the energy release performance of advanced molecular perovskite energetic materials. Full article

Rising triple-negative breast cancer (TNBC) cases and Candida infection risks during chemotherapy demand novel therapies, with metal-oxide nanocomposites emerging as a promising solution. In this study, we synthesized Ag-ZnO and Cu-ZnO nanocomposites as established quantitative links between their physicochemical properties, ion release behaviour, and biological activity, evaluating antifungal effects against Candida albicans (ATCC 90028) and Saccharomyces cerevisiae (ATCC 9763), and their anticancer potential against MDA-MB-231 cells (ATCC HTB-26). The results revealed Ag (~13–19 nm) and Cu (~4–8 nm) nanoparticles dispersed in a ZnO matrix, with XPS confirming mixed Ag⁰/Ag(I)/Ag(III) and Cu(I)/Cu(II) speciation. Ag-ZnO NC exhibited strong antifungal activity (MIC = 25 mg L⁻¹) against both fungi, while Cu-ZnO NC was only effective (MIC = 100 mg L⁻¹) against S. cerevisiae. Aqueous release of Ag⁺ was ~2.6-fold higher than Cu²⁺. Ag-ZnO NC induced marked ROS generation (~6-fold higher than S. cerevisiae) and dehydrogenase inhibition (6.6- and ~20-fold, respectively). ATR-FTIR linked species-specific susceptibility to cell-wall architecture. SEM confirmed membrane destabilization and perforation. In MDA-MB-231, necrotic fractions reached ~9% and >40% for Ag-ZnO and Cu-ZnO, respectively. Both metal oxide nanocomposites (MONCs) act through ion release, revealing a selectivity window, especially for Ag-ZnO. Further studies on non-cancerous cells, ion-release kinetics, uptake and in vivo validation are essential to establish a therapeutic index. Full article