Nanomaterials and Nanotechnology

In this study, Arabic gum-capped ZnO NPs (ZnO NPs-Cap) were synthesized via a simple precipitation method, and a comparative study was performed with uncapped ZnO. The synthesized nanoparticles (NPs) were characterized using UV–visible (UV-vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDS) coupled with scanning electron microscopy (SEM). The absorption peak of ZnO NPs-Cap appeared at 366.5 nm, and the calculated band gap energy was 3.38 eV. Antibacterial activity was assessed against gram positive and negative foodborne pathogens. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of ZnO NPs and ZnO NPs-Cap against S. aureus, Bacillus cereus, E. coli and S. typhimurium bacterial strains revealed a clear superiority of ZnO NPs-Cap than uncoated ZnO. Time–kill assays performed at different concentrations and times has demonstrated a time-dependent reduction in bacterial viability for both formulations. The present study demonstrates that Arabic gum capping enhances the dispersion, stability, and antibacterial efficacy of ZnO NPs. The findings also provide useful insight into the biological activity and potential eco-toxicological implications of biopolymer-modified ZnO nanomaterials.

Lignin, a renewable aromatic polymer found in lignocellulosic biomass, has several potential uses due to its antioxidant, antibacterial, and UV-absorbing qualities. The aim of this work was to extract soda lignin for sunscreen, antioxidant, and antibacterial properties from Oxytenanthera abyssinic (Ethiopian lowland bamboo) stems using an alkaline treatment. A 1, 4-dioxane-based nanoprecipitation technique was then used to create lignin nanoparticles produced from O. abyssinica (OA-LNPs) via a self-assembly process. The extraction procedure was optimized with temperature (23–120°C), time (1–24 hours) and NaOH concentration (5–15%). 1, 4-Dioxane-based nanoprecipitation was used to synthesis OA-LNPs which were then examined using SEM, EDX UV-Vis, FTIR and ¹HNMR for morphology size zeta potential and chemical structure. Antioxidant activity using DPPH assays, sun protection factor (SPF) measurements in commercial lotions and antibacterial testing against Gram-positive (S. aureus and S. epidermidis) and Gram-negative (E. coli and K. pneumoniae) strains were among the functional evaluations. Up to 294 mg/g of soda lignin were produced by the extraction. OA-LNPs had a spherical shape size ranging from 65 to 135 nm (mean 115 nm) a zeta potential of -30. 1 mV and no sulfur was found. They also retained phenolic and aromatic functionalities. The antioxidant activity of OA-LNPs was 11. 47 µg/mL which was higher than that of soda lignin (131.1 µg/mL). Due to UV absorption by phenolic groups SPF evaluations showed improvements in commercial lotions up to 114.8±1.3 when OA-LNPs were added. Antibacterial testing showed moderate efficacy against the tested strains with inhibition zones ranging from 12.43± 0.90 to 28.8± 1.11 mm. With better bioavailability and multifunctionality than Soda lignin (SL) these results highlight the environmentally friendly valorization of lignin from underutilized biomass and position OA-LNPs as promising candidates for sustainable applications in food packaging cosmetics and biomedicine.

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Using zinc nitrate hexahydrate as the precursor and Rhus vulgaris fruit extract as a natural reducing and capping agent, this study describes the environmentally friendly synthesis of zinc oxide nanoparticles (RV-ZnONPs). The presence of bioactive substances like phenols, flavonoids, tannins, alkaloids, saponins, terpenoids, steroids and glycosides responsible for the reduction of Zn²⁺ ions nucleation and stabilization of ZnONPs. UV-Vis spectroscopy, X-ray diffraction (XRD), zeta potential analysis (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared (FT-IR) spectroscopy were used to characterize the biosynthesized RV-ZnONPs. A distinctive absorption peak with an estimated band gap energy of 3.20 eV was found by UV–Vis analysis at approximately 371 nm. While TEM images revealed primarily irregular nanoparticles with an average size of ∼23. 5 nm, XRD confirmed the formation of highly crystalline ZnONPs with a hexagonal wurtzite structure and an average crystallite size of ∼22.7 nm. Excellent colloidal stability was demonstrated by the high negative zeta potential value (−35.1 mV) and FT-IR analysis verified the role of functional groups derived from plants in capping and stabilizing nanoparticles. The photocatalytic, antioxidant, and antibacterial properties of RV-ZnONPs were also assessed. Under UV irradiation, the RV-ZnONPs demonstrated effective photocatalytic degradation with maximum degradation rate of 65.4%. The degradation efficiency rose with nanoparticle concentration and reaction time. Antioxidant activity assessed by the DPPH assay demonstrated concentration-dependent free-radical scavenging with RV-ZnONPs showing a significantly lower IC₅₀ value (74.46 µg/mL) compared to the extract from crude fruit. Furthermore RV-ZnONPs demonstrated significant antibacterial activity against Staphylococcus aureus and Escherichia coli which was ascribed to membrane disruption, reactive oxygen species generation, and Zn²⁺ ion release. This study highlights the promising potential of Rhus vulgaris fruit extract for environmental remediation antioxidant applications and antimicrobial treatments by demonstrating that it offers an efficient green pathway for the synthesis of stable and multifunctional ZnONPs.

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Titanium dioxide (TiO₂) exhibits dielectric properties that vary significantly with its physical morphology and thermal history. This work evaluates the dielectric responses of calcined nanopowder, electrospun nanofibers before and after heat treatment. Utilizing TEM, SEM, EDX, FTIR, and XRD allows for a detailed assessment of the morphological, and structure differences across the TiO₂ samples. The uncalcined nanofibers exhibit an amorphous structure with significant polyvinylpyrrolidone (PVP) content. Calcination transforms these amorphous precursors into crystalline fibers with a mixed anatase and rutile phase. Dielectric measurements carried out over a frequency range of 1 Hz to 1 MHz demonstrated that the calcined nanofibers feature a dielectric constant (ε′) that is both reduced and mostly stable across the measured frequency range. At higher frequencies, the dielectric constant was found to approach free-space permittivity, with the material additionally exhibiting low dielectric loss (ε″, tan δ), and reduced low AC conductivity (σ). The calcined TiO₂ nanopowders, and uncalcined fibers by contrast revealed higher ε′ values and more substantial losses. The calcined TiO₂ nanofibers thus exhibit superior insulating characteristics, demonstrating that nanostructuring combined with controlled thermal treatment can be effectively employed to alter dielectric performance. These findings carry meaningful implications for designing dielectric materials, particularly in enabling the optimization of low and stable dielectric permittivity alongside low-loss properties across a broad frequency range for electronic circuits applications.

The electronic and structural properties of silicene, multilayer silicene, and 2D silicon films, synthesised on Ag(111), Au(111) and on the α- and β-phase Si(111)√3 × √3R30°-Bi, have been reviewed according to the results of investigations made by low energy electron diffraction, Auger electron spectroscopy, grazing-incidence X-ray diffraction, low/high electron energy diffraction, reflection electron energy loss, scanning tunnelling microscopy as well as spectroscopy, and density functional theory calculations. The findings revealed the successful growth of silicene and multilayer silicene on Ag(111) single crystal, and on the α-phase Si(111)√3 × √3R30°-Bi, while, at variance, two-dimensional Si islands (2D Si) still showing the √3 × √3R30° reconstruction, parallel to that of bismuth, were obtained on the β-phase Si(111)√3 × √3R30°-Bi. Single layer of blue phosphorus synthesised on Au(111) single crystal and on Te/Au(111), were also reviewed, and compared to silicene deposited on Ag(111) single crystal, as well as to their first-principles density functional theory calculations to show their interesting structural properties.

Ultrafine nano-silica, with its smaller particle size compared to conventional nano-silica, is typically synthesized via gas-phase methods that require complex raw materials and processes. Here, we report optimized conditions for preparing ultrafine nano-silica via a precipitation reaction between fluosilicic acid waste and aluminum hydroxide. The optimal conditions determined were as follows: reverse feeding, surfactant addition at 3.0%, aluminum-to-silicon ratio of 2.00, reaction time of 30 min, reaction temperature of 90 °C, and stirring rate of 250 rpm. Under these conditions, ultrafine nano-silica with a uniform particle size of approximately 11 nm was successfully synthesized. Characterization of samples prepared by different feeding methods showed that the reverse feeding method yielded ultrafine nano-silica with superior performance indicators compared to the forward feeding method. Analysis of system changes during synthesis indicated that the feeding method influenced the acidic or alkaline environment of the substrate, affecting SiF₄ hydrolysis and the subsequent dehydration and condensation of Si-(OH)₄ monomers, leading to variations in silica particle agglomeration. Further, an analysis of the effects of alkyl chains in surfactants on the surfaces of silica particles, including -OH substitution or Si-O-Si bond cleavage, provided insights into the action mechanism of surface groups on ultrafine nano-silica particles.

Waterproof dam concrete’s permeability stability in goaf waterlogged environments critically impacts coal mine safety and groundwater sustainability. Underwater immersion, weak infiltration pathways are formed at the joint interfaces of the composite structure (concrete-concrete), potentially triggering water damage incidents. Optimization research on interface anti-seepage performance is urgently required. This study focuses on the composite structure of waterproof concrete dams, analyzing permeability modification by nano SiO₂/TiO₂/Al₂O₃ at varying percentages on bi-material specimens post-immersion. Gas permeability, Liquid-measured porosity test, Ultrasonic velocity, and SEM were performed to evaluate the permeability evolution and interface stability of nanomaterial-modified concrete after different days of water immersion. Results indicate that post 14-day immersion, the permeability of ordinary concrete monomer specimens (OC) and bi-material specimens (C-C) increased to 0.236×10^-5μm² and 0.760×10^-3μm², respectively, corresponding to degradation levels of 220.5% and 88.5%. Moreover, the permeability of C-C remained two orders of magnitude higher than that of OC, and their degradation followed a three-stage pattern: rapid amplification, moderate development, and gradual stabilization. Nanomaterial incorporation suppressed permeability deterioration, particularly the 0.5% TiO₂ group, showing optimal performance. Post-immersion, the 0.5%TiO₂ group showed 0.236×10^-3μm² permeability, representing a 69.0% improvement relative to the C-C. Other groups demonstrated modification effects of 55.9% for 0.5%Al₂O₃, 52.6% for 1.0%Al₂O₃, 42.1% for 1.0%TiO₂, and 24.4% for 0.5%SiO₂, while the addition of 1.0%SiO₂ exhibited no significant improvement. Liquid-measured and ultrasonic tests showed the 0.5% TiO₂ group had 16.4% lower porosity and 14.2% higher wave velocity post-immersion. SEM analysis demonstrated that nano-TiO₂ effectively suppressed the expansion of interface cracks, and image binarization processing revealed a 49.6% reduction in fracture surface porosity in the 0.5%TiO₂ group, resulting in a denser interface microstructure and enhanced permeability stability. This study establishes key technical foundations for optimizing composite structural materials for waterproof concrete dams, thereby enhancing permeability stability in underground storage facilities and related engineering structures.