Search Results (526)

This study reports on green-synthesized zinc oxide nanoparticles (ZnONPs), focusing on their physicochemical characterization, photocatalytic properties, and agricultural applications. Dynamic light scattering (DLS) analysis revealed a mean hydrodynamic diameter of 337.3 nm and a polydispersity index (PDI) of 0.400, indicating moderate polydispersity and nanoparticle aggregation, typical of biologically synthesized systems. High-resolution transmission electron microscopy (HR-TEM) showed predominantly spherical particles with an average diameter of ~28 nm, exhibiting slight agglomeration. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of zinc and oxygen, while X-ray diffraction (XRD) analysis identified a hexagonal wurtzite crystal structure with a dominant (002) plane and an average crystallite size of ~29 nm. Photoluminescence (PL) spectroscopy displayed a distinct near-band-edge emission at ~462 nm and a broad blue–green emission band (430–600 nm) with relatively low intensity. The ultraviolet–visible spectroscopy (UV–Vis) absorption spectrum of the synthesized ZnONPs exhibited a strong absorption peak at 372 nm, and the optical band gap was calculated as 2.67 eV using the Tauc method. Fourier-transform infrared spectroscopy (FTIR) analysis revealed both similarities and distinct differences to the pigeon extract, confirming the successful formation of nanoparticles. A prominent absorption band observed at 455 cm⁻¹ was assigned to Zn–O stretching vibrations. X-ray photoelectron spectroscopy (XPS) analysis showed that raw pigeon droppings contained no Zn signals, while their extract provided organic biomolecules for reduction and stabilization, and it confirmed Zn²⁺ species and Zn–O bonding in the synthesized ZnONPs. Photocatalytic degradation assays demonstrated the efficient removal of pollutants from sewage water, leading to significant reductions in total dissolved solids (TDS), chemical oxygen demand (COD), and total suspended solids (TSS). These results are consistent with reported values for ZnO-based photocatalytic systems, which achieve biochemical oxygen demand (BOD) levels below 2 mg/L and COD values around 11.8 mg/L. Subsequent reuse of treated water for irrigation yielded promising agronomic outcomes. Wheat and barley seeds exhibited 100% germination rates with ZnO NP-treated water, which were markedly higher than those obtained using chlorine-treated effluent (65–68%) and even the control (89–91%). After 21 days, root and shoot lengths under ZnO NP irrigation exceeded those of the control group by 30–50%, indicating enhanced seedling vigor. These findings demonstrate that biosynthesized ZnONPs represent a sustainable and multifunctional solution for wastewater remediation and agricultural enhancement, positioning them as a promising candidate for integration into green technologies that support sustainable urban development. Full article

This study presents a green, single-step method for synthesizing nanocomposites based on reduced graphene oxide (RGO) and gold nanoparticles (AuNPs), using sodium citrate as a mild reducing and stabilizing agent. AuNPs were generated from chloroauric acid (HAuCl₄) directly on the surface of graphene oxide (GO), which was simultaneously reduced to RGO. Structural characterization via Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Selected Area Electron Diffraction (SAED) confirms spherical AuNPs (10–60 nm) distributed on RGO sheets, with indications of nanoparticle aggregation. Dynamic Light Scattering (DLS) and zeta potential analysis support these findings, suggesting colloidal instability with higher RGO content. Biological evaluation demonstrates dose-dependent cytotoxicity in HaCaT keratinocytes, with IC₅₀ values (half maximal inhibitory concentration) decreasing as RGO content is increased. At moderate dilutions (1–25 µL/100 µL), the composites show acceptable cell viability (>70%). Antibacterial assays reveal strong synergistic effects against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, with sample RGO/Au 0.500/0.175 g/L showing complete E. coli inhibition at low Au content (0.175 g/L). The composite retained activity even in protein-rich media, suggesting potential for antimicrobial applications. These findings highlight the potential of RGO/AuNPs composites as multifunctional materials for biomedical uses, particularly in antimicrobial coatings and targeted therapeutic strategies. Full article

Foodborne illnesses remain a global challenge, requiring rapid and sensitive detection platforms. We developed a magnetosome-based electrochemical immunosensor for lipopolysaccharide (LPS) antigens from Escherichia coli and Salmonella typhimurium. Magnetosomes isolated from Magnetospirillum sp. RJS1 were characterized by HR-TEM and functionalized with antibodies (2 CFU mL⁻¹), with FTIR confirming successful conjugation. The antibody–magnetosome complexes were immobilized on a chitosan/glutaraldehyde-modified glassy carbon electrode. AFM revealed globular (200–700 nm) and island-like (1–3 µm) features after antigen binding. Electrochemical impedance spectroscopy showed stepwise increases in charge-transfer resistance upon electrode modification and antigen interaction. The sensor exhibited high sensitivity toward E. coli (3–7 CFU mL⁻¹) and Salmonella (3–8 CFU mL⁻¹), achieving an immune sensitivity of 36.24 Ω/CFU mL⁻¹ and a detection limit of 1 CFU mL⁻¹. These results demonstrate the potential of magnetosome-based immunosensors as portable, efficient platforms for the rapid detection of foodborne pathogens in real samples. Full article

Precision and real-time detection of hydrogen peroxide (H₂O₂) are essential in pharmaceutical, industrial, and defence sectors due to its strong oxidizing nature. In this study, silver (Ag)-doped CeO₂/Ag₂O-modified glassy carbon electrode (Ag-CeO₂/Ag₂O/GCE) has been developed as a non-enzymatic electrochemical sensor for the sensitive and selective detection of H₂O₂. The synthesized Ag-doped CeO₂/Ag₂O nanocomposite was characterized using various advanced techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). Their optical, magnetic, thermal, and chemical properties were further analyzed using UV–vis spectroscopy, electron paramagnetic resonance (EPR), thermogravimetric-differential thermal analysis (TG-DTA), and X-ray photoelectron spectroscopy (XPS). Electrochemical sensing performance was evaluated using cyclic voltammetry and amperometry. The Ag-CeO₂/Ag₂O/GCE exhibited superior electrocatalytic activity for H₂O₂, attributed to the increased number of active sites and enhanced electron transfer. The sensor displayed a high sensitivity of 2.728 µA cm⁻² µM⁻¹, significantly outperforming the undoped CeO₂/GCE (0.0404 µA cm⁻² µM⁻¹). The limit of detection (LOD) and limit of quantification (LOQ) were found to be 6.34 µM and 21.1 µM, respectively, within a broad linear detection range of 1 × 10⁻⁸ to 0.5 × 10⁻³ M. The sensor also demonstrated excellent selectivity with minimal interference from common analytes, along with outstanding storage stability, reproducibility, and repeatability. Owing to these attributes, the Ag-CeO₂/Ag₂O/GCE sensor proved effective for real sample analysis, showcasing its potential as a reliable, non-enzymatic platform for H₂O₂ detection. Full article

With the aim of reducing catalysts’ cost while maintaining high performance in water splitting, ZnO and RuO₂ were combined into composites with ZnO to RuO₂ mass ratios of 1:1, 2:1, and 10:1. The ZnO/RuO₂ composites were prepared by microwave processing of a suspension containing Zn(OH)₂ in situ precipitated onto RuO₂ powder, and subsequently thermally modified at 600 °C to promote heterojunction formation and alter the defect chemistry. Phase composition, crystal structure, morphology, and optical properties were analyzed in detail employing XRD, TEM/HRTEM, HAADF-STEM with EDS, PL and XPS spectroscopy. The photoelectrocatalytic (PEC) activity of the composites toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was evaluated by linear sweep voltammetry in alkaline electrolyte (0.1 M NaOH, pH 13), before and after one hour of electrochemical system illumination. The analysis focused on surface and bulk oxygen vacancies, which may have a crucial impact in PEC activity, by (1) promoting charge separation and increasing the number of active sites thus enhancing PEC activity, or (2) acting as electron–hole traps and recombination centers, reducing the lifetime of photo-induced charge carriers and thus deteriorating PEC activity. The presented results demonstrate that the combination of ZnO with RuO₂ in a specific mass ratio, along with controlled defect structure, offers a worthwhile route for developing bifunctional, noble-metal-reduced catalysts for green hydrogen and oxygen production. Full article

In this study, MnO₂-CNTs composite support was prepared by citric acid reduction method, and then, Pt nanoparticles were loaded on the surface by ethylene glycol reduction method to obtain a series of Pt/xMnO₂-CNTs catalysts. Structural characterization (TEM, XRD, HRTEM) showed that Pt nanoparticles were uniformly dispersed on the surface of the catalyst with an average particle size of 3.6 nm. Electrochemical tests show that when the content of MnO₂ is 20 wt.%, the Pt/_20wt.%MnO₂-CNTs catalyst has the best methanol oxidation performance, and its mass activity and long-term stability are 4.0 times and 5.41 times that of commercial Pt/C, respectively. The in situ FTIR results showed that MnO₂ promoted the dissociation of water through synergistic effect, generated abundant OH species, accelerated the oxidation of CO intermediates, and inhibited the poisoning of Pt sites. In this study, it is clear that the excellent performance of Pt/xMnO₂-CNTs is due to multiple synergistic effects. Modified carbon nanotubes facilitate proton conduction, Pt nanoparticles effectively activate methanol, and MnO₂ modulates reaction intermediates via its bifunctional mechanism. This comprehensive mechanism understanding provides a theoretical basis for the design of high-performance catalysts for direct methanol fuel cells. Full article

This study investigates the effect of tensile strain during high-temperature carbonization on the microstructural development and mechanical properties of polyacrylonitrile (PAN)-based carbon fibers. The wet-spun stabilized PAN precursor fibers were carbonized at 1400 °C under various tensile draw ratios (0%, 5%, 10%, and 15%), followed by stress-free graphitization at 2400 °C in an argon atmosphere for 1 h to isolate the effects of the carbonization-stage tension. Structural characterization using XRD, 2D-XRD, Raman spectroscopy, and HR-TEM revealed that moderate tensile strain (5–10%) promoted significant improvements in crystallinity, orientation, and graphene layer alignment. Notably, the fiber drawn at 10% performed the best, with a reduced interlayer spacing (d₀₀₂), increased lateral crystallite size (L_a), high orientation factor, and minimal turbostratic disorder. These structural developments translated into the best mechanical properties, including a tensile strength of ~2.44 GPa, a Young’s modulus of ~408.6 GPa, and the highest measured density (1.831 g/cm³). In contrast, excessive strain (15%) induced microstructural defects and reduced performance, underscoring the detrimental effects of overstretching. The findings highlight the critical role of draw control during carbonization in optimizing the structure–property relationships of carbon fibers, offering valuable insight for the design of high-performance fiber processing strategies. Full article

The development of electrocatalysts composed of earth-abundant elements is essential for advancing the commercial application of Proton Exchange Membrane Fuel Cells (PEMFC). Among these, single-atom electrocatalysts, such as Fe-N-C, show great promise for the oxygen reduction reaction (ORR). This study aims to improve the ORR activity and stability of Fe-N-C electrocatalysts by fine-tuning the straightforward 1,10-phenanthroline-iron complexation synthesis method. Key parameters, including iron-to-phenanthroline ratio, carbon powder surface area, and pyrolysis temperature were systematically varied to evaluate their influence on the resulting electrocatalysts. The findings of this study revealed that the electrocatalysts synthesized with 1,10-phenanthroline (Phen) and high-surface-area Black Pearls (BP) possessed much better ORR activity than electrocatalysts prepared by using Vulcan carbon (lower surface area). Interestingly, electrocatalysts prepared with BP, but with a non-bidentate nitrogen-containing ligand molecule, such as imidazole, showed a much poorer activity, as the resulting material predominantly consisted of inactive structures, such as encapsulated iron nanoparticles and iron oxide, as evidenced by HR-TEM, EXAFS, and XRD. Therefore, the results suggest that only the synergistic combination of the bidentate ligand phenanthroline (Phen) and the high-surface-area carbon support (BP) favored the formation of ORR-active Fe-N-C single-atom species upon pyrolysis. The study also unveiled a significant enhancement in electrocatalyst stability during accelerated durability tests (and air storage) as the pyrolysis temperature was increased from 700 to 1300 °C, albeit at the expense of ORR activity, likely resulting from the generation of iron particles. Pyrolysis at 1050 °C yielded the electrocatalyst with the most favorable balance of activity and stability in rotating disk measurements, while maintaining moderate durability under PEM fuel cell operation. The insights obtained in this study may guide the development of more active efficient and durable electrocatalysts, synthesized via a simple method using earth-abundant elements, for application in PEMFC cathodes. Full article

The structural features of Sb–doped (Ti,Zr)NiSn and (Ti,Zr,Hf)NiSn half-Heusler (HH) thermoelectrics have been identified down to the atomic scale using a combination of transmission electron microscopy (TEM) techniques. TEM sheds light on the morphology, phases present, size distributions and elemental variations between the two samples. Both materials consist of the HH phase, at both micro- and nanoscale levels, and comprise particles with two size ranges, 115 and 223 nm, on average, for large HH particles and 4–17 nm for nanoparticles for both materials. Hf incorporation in the HH lattice brought upon significant elemental fluctuations, manifested in chemical profiles and lattice parameter variations measured by post-experimental image analysis. The increased elemental variations induced by Hf substitution significantly contributed to the low thermal conductivity values and high power factor, leading to an enhanced figure of merit of 0.76 at 762 K for (Ti,Zr,Hf)NiSn, demonstrating the capability of TEM to confirm the structural features that are responsible for improved TE performance. Full article

Amino acids are not just monomers of proteins, but they can also carry biological functions. L-cysteine (Cys), L-proline (Pro), L-asparagine (Asn), and L-glutamic acid (Glu) were used to evaluate how different amino acid chemistries alter the morphology and size of the silver nanoparticles (AgNPs) synthesized in the presence of two carbohydrate ligands, which were lactose methoxyaniline (LMA) and galactose 5-aminosalicylic acid (G5AS). UV–vis, infrared (IR), High-Resolution Transmission Electron Microscopy (HR-TEM) and X-ray diffraction (XRD) characterizations revealed that the effect of amino acids on the characteristics of the AgNPs showed dependence on the carbohydrate ligand chemistry. In the case of LMA, AgNPs shifted from aggregates to anisotropic nanoparticles, larger aggregates, and a mixture of anisotropic and 1D nanoparticles in the presence of Cys, Glu, Asn and Pro amino acids, respectively. In contrast to this, the introduction of Cys and Asn caused the formation of cluster-like AgNPs and larger rounded nanoparticles, while G5AS-synthesized AgNPs were multigonal 0D particles. Moreover, Glu and Pro contributed the resistance of silver oxide formation on the particles. Antibacterial characterization showed that LMA_Glu_AgNPs were the most effective ones, while LMA_Cys_AgNPs and G5AS_Cys_AgNPs, which were the smallest AgNPs, did not show any significant antibacterial activity. Full article

We investigated the influence of gold deposition on the magnetic behavior, biocompatibility, and bioactivity of CoFe₂O₄ (MCF) nanomaterials (NMs) functionalized with sodium citrate (Cit) or glycine (Gly). The resulting multifunctional plasmonic nanostructured materials (MCF-Au-L, where L is Cit, Gly) exhibit superparamagnetic behavior with magnetic saturation of 59 emu/g, 55 emu/g, and 60 emu/g, and blocking temperatures of 259 K, 311 K, and 322 K for pristine MCF, MCF-Au-Gly, and MCF-Au-Cit, respectively. The MCF NMs exhibit a small uniform size (with a mean size of 7.1 nm) and an atomic ratio of Fe:Co (2:1). The gold nanoparticles (AuNPs) show high heterogeneity as determined by high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX). The UV-Vis spectroscopy of the composites reveals two localized surface plasmons (LSPs) at 530 nm and 705 nm, while Fourier Transformed-Infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirm the presence of Cit and Gly on their surface. Subsequent biocompatibility tests confirm that MCF-Au-L NMs do not exert hemolytic activity (hemolysis < 5%). In addition, the CCK-8 viability assay tests indicate the higher sensitivity of cancerous cells (A549) to the photoactivity of MCF-Au compared to healthy Detroit 548 (D548) cell lines. We use advanced microscopy techniques, namely atomic force, fluorescence, and holotomography microscopies (AFM, FM, and HTM, respectively) to provide further insights into the nature of the observed photoactivity of MCF-Au-L NMs. In addition, in situ radiation, using a modified HTM microscope with an IR laser accessory, demonstrates the photoactivity of the MCF-Au NMs and their suitability for destroying cancerous cells through photodynamic therapy. The combined imaging capabilities demonstrate clear morphological changes, NMs internalization, and oxidative damage. Our results confirm that the fabricated multifunctional NMs exhibit high stability in aqueous solution, chemical solidity, superparamagnetic behavior, and effective IR responses, making them promising precursors for hybrid cancer therapy. Full article

Objectives: In this research study, we introduce a novel approach to develop an innovative nanocarrier system comprising gold nanoparticles (GNPs) loaded with doxorubicin (D) in combination with natural molecules, such as trans-resveratrol (R), piperine (P), and icariin (Ic), against human cervical cancer. The final objective is to improve the anticancer efficacy of doxorubicin on HeLa and CaSki cell lines. Methods: Resveratrol was also used for the synthesis of GNP_R1 nanoparticles. Multi-functional GNPs loaded with D, R, P, and Ic (e.g., GNP_R1@D/R/P/Ic) were successfully prepared and fully characterized by SPR, TEM, HR-TEM, XRD, AFM, DLS, and zeta potential. They were investigated for in vitro stability in various biological media. The cytotoxicity activity was tested on HeLa and CaSki cell lines, using the MTT assay, for their applications as anticancer agents. Results: Our results demonstrate that the novel multi-functional GNPs (such as GNP_R1@D/R and GNP_R1@D/R/P/Ic) can effectively target the cervical cancer cells, improving the bioavailability of therapeutic agents and enhancing their cytotoxicity against cervical cancer cells. In vitro assessments demonstrated that the multi-functional GNPs exhibited improved stability and potential anticancer efficacy on human cervical cancer cells. Conclusions: The described strategy connects the benefits of biomolecules with functional nanoparticles toward the development of various GNP_R1@D/R/P/Ic nanocarriers for their applications as anticancer agents against human cervical cancer. This study provides compelling evidence that the innovative nanoparticles can enhance the therapeutic efficacy of doxorubicin against cervical cancer and offer a more advantageous alternative compared to doxorubicin monotherapy. Full article

GTD 111 has been employed in first-stage blades in different gas turbines. The study of microstructural evolution is essential for the lifetime assessment and development of turbine blades. The microstructural stability of a 130 MW gas turbine first-stage blade at 800 °C was studied. The microstructure’s evolution was analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic calculation. As thermal exposure time increases, the shape of γ′ precipitates changes from square to spherical. During thermal exposure, MC particles formed and coarsened along the grain boundaries, and primary MC carbide decomposed into the η phase and M₂₃C₆. The stability of MC carbide at the grain boundaries was lower than that within the grains. MC carbide precipitated at the grain boundaries tends to grow along the boundaries and eventually forms elongated carbide. High-resolution transmission electron microscopy (HRTEM) images indicate that the orientation of the γ′ precipitate changes during the coarsening process. The GTD 111 alloy can be deformed through dislocation shearing at 800 °C. The hardness value initially increases, then decreases with further exposure, which is related to the reduced precipitation strengthening by γ′ precipitates and the reduction in the hardness of the γ matrix. Full article

In the present study, we synthesized fluorocarbon-coated cobalt ferrite (CoFe₂O₄) magnetic nanoparticles using alkoxysilanes such as trimethoxy(3,3,3-trifluoropropyl)silane (TFPTMS), trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane (NFHTMS), and triethoxy(1H,1H,2H,2H-perfluorodecyl)silane (PFDTES). The synthesized nanoparticles were characterized by various techniques, including X-ray diffractometry (XRD), transmission electron microscopy (TEM/HRTEM/EDXS), Fourier transform infrared spectroscopy (FTIR), specific surface area measurements (BET), and magnetometry (VSM). To understand their surface characteristics, contact angle (CA) measurements were carried out, providing valuable insights into their hydrophobic properties. Among the samples of CoFe₂O₄ coated with fluoroalkoxysilanes, those with PFDTES surface coating had the highest water contact angle of 159.2°, indicating their superhydrophobic character. The potential of the prepared fluoroalkoxysilane-coated CoFe₂O₄ nanoparticles for the removal of waste low-SAPS synthetic engine oil from a model aqueous solution was evaluated based on three key parameters: adsorption efficiency (%), adsorption capacity (mg/g), and desorption efficiency (%). All synthesized CoFe₂O₄ samples coated with fluoroalkoxysilane showed high oil adsorption efficiency, ranging from 87% to 98%. The average oil adsorption capacity for the samples was as follows: F₃-SiO₂@CoFe₂O₄ (3.1 g of oil/g of adsorbent) > F₉-SiO₂@CoFe₂O₄ (2.7 g of oil/g of adsorbent) > F₁₇-SiO₂@CoFe₂O₄ (1.5 g of oil/g of adsorbent) as a result of increasing oleophobicity with increasing fluorocarbon chain length. The desorption results, which showed 77–97% oil recovery, highlighted the possibility of reusing the adsorbents in multiple adsorption/desorption cycles. Full article

Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these issues, a novel NiP@PNC/NF electrocatalyst was developed via a one-step thermal annealing process under nitrogen, integrating nickel phosphide (NiP) with phosphorus and nitrogen co-doped carbon nanotubes (PNCs) on a nickel foam (NF) substrate. This design enhances catalytic activity and charge transfer, achieving current densities of 50 mA cm⁻² at 1.34 V and 100 mA cm⁻² at 1.43 V versus the reversible hydrogen electrode (RHE). The electrode’s high electrochemical surface area (235 cm²) and double-layer capacitance (94.1 mF) reflect abundant active sites, far surpassing NiP/NF (48 cm², 15.8 mF) and PNC/NF (39.5 cm², 12.9 mF). It maintains exceptional stability, with only a 16.3% performance loss after 35 h, as confirmed by HR-TEM showing an intact nanostructure. Our single-step annealing technique provides simplicity, scalability, and efficient integration of NiP nanoparticles inside a PNC matrix on nickel foam. This method enables consistent distribution and robust substrate adhesion, which are difficult to attain with multi-step or more intricate techniques. Full article