Green synthesis of metal oxide nanoparticles, and their various applications

Enhancement of Rice Zinc Content Using Green Synthesized ZnO-NPs by Foliar and Nano-Priming Applications

Zinc oxide nanoparticles (ZnO-NPs) can enhance zinc bioavailability in plants, improving crop nutritional quality and addressing global zinc deficiency. This study aimed to investigate the effects of zinc oxide nanoparticles (ZnO-NPs), obtained by a green synthesis method, on the growth, yield parameters, and zinc content of rice plants. In the study, two different application strategies of ZnO-NPs on rice plants were evaluated, i.e., foliar spray and seed priming. To compare the effects of these application strategies, rice plants were treated with ZnO-NPs at two different concentrations, 25 mg/L and 50 mg/L. Effects of ZnO-NPs on plant growth (shoot and root length, fresh and dry mass), chlorophyll and carotenoid content, grain yield and zinc content were investigated. The results showed that both ZnO-NP application methods increased rice growth and yield, especially the combined method (seed priming + foliar spray) provided the highest efficiency. It was observed that seed zinc content was increased up to 10% by seed priming method and foliar spray application increased the zinc content up to 23% while the combination of seed priming and foliar spray increased zinc content up to 122%. In general, applications at 50 mg/L concentration increased more than 25 mg/L. These results indicate that ZnO-NPs can be an effective tool for zinc deficiency management in agricultural practices and can improve the yield and nutritional content of staple foods such as rice.

A paradigm of microbe-mediated green nano-semiconductors and nano-metals

Semiconducting and metallic nanomaterials are essential building blocks for developing modern-age technologies, and their demand is expanding exponentially with a growing population. However, their processing impacts the ecosystem and requires urgently sustainable solutions. This perspective underlines the emergence of microbe-mediated (bacteria, yeast, fungi, microalgae, viruses, cyanobacteria) green nanomaterials, including metal-based, carbon-based, organic and hybrid nanomaterials, with technical challenges of scalability, stability and cytotoxicity restricting their transition from lab-to-market. Besides, it discusses alternative solutions by integrating digital-age technologies like artificial intelligence to establish these green nano-semiconductors/metals for multidimensional applications and subsidizing the UN's sustainable development goals and one health management.

Assessment of the bioactivity of bioinspired magnesium oxide nanoparticles from the Azadirachta indica extract

Azadirachta indica (neem) extract was used to biologically synthesize magnesium oxide nanoparticles (MgO NPs). The synthesized NPs were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and UV-vis spectroscopy. Antioxidant, anticancer, antibacterial, antidiabetic, and anti-inflammatory activities were analyzed for the synthesized MgO NPs and neem extract. The obtained results confirmed the synthesis of spherical magnesium oxide nanoparticles with an average particle size of 23 nm using XRD. The samples exhibited good thermal stability and high stability in biological media. Compared to the neem extract and chemically synthesized magnesium oxide nanoparticles, the bioinspired magnesium oxide nanoparticles showed considerable free radical scavenging activity, with an IC50 value of 69.03 μg/mL. In addition, they reflected high selectivity to liver hepatic cancer cells with an IC50 value of 94.85 μg/mL without inducing any damage to human umbilical vein endothelial cells. The antibacterial activity of the bioinspired magnesium oxide nanoparticles demonstrated comparable effectiveness in treating both Gram-positive and Gram-negative bacterial strains. Furthermore, the produced bioinspired magnesium oxide nanoparticles showed a high percentage of inhibition for both α-amylase and α-glucosidase enzymes with an IC50 value of 61. 53 and 50.6 μg/mL, respectively. In addition, the bioinspired magnesium oxide nanoparticles also showed a higher denaturation inhibition percentage with an IC50 value of 6.66 μg/mL, indicating strong anti-inflammatory action. These enhanced abilities usher in a new bioinspired magnesium oxide nanoparticle bio-application era. Consequently, further in vivo studies are needed to assess the kinetic properties of these nanoparticles.

Green Synthesis of CuO Nanoparticles-Structural, Morphological, and Dielectric Characterization

This study investigates the structural, chemical, and morphological properties of CuO nanoparticles synthesized via a green synthesis route using Opuntia ficus-indica cladode extract, with a focus on the effects of stepwise versus direct calcination. Raman spectroscopy revealed the presence of CuO, Na2CO3, and Na2SO3, with the latter two being associated with elements inherited from the cactus extracts. XRD patterns confirmed the presence of crystalline CuO and Na2CO3 phases, with the low content of Na2SO3 inferred to be amorphous. Rietveld refinement estimated a CuO content of approximately 77% in the stepwise-calcined sample and 75% in the directly calcined sample, with lattice parameters closely aligning with reference values. SEM micrographs revealed a tendency for CuO nanoparticles to aggregate, likely due to high surface energy and interaction with the viscous plant extract used in the green synthesis. Crystallite size estimates, along with morphological observations, suggest that stepwise calcination enhances crystallinity and particle definition without altering the fundamental nanoparticle morphology. These findings highlight the influence of calcination method and natural extracts on the composition and morphology of green-synthesized CuO nanoparticles, offering insights into potential applications, namely in microelectronics, due to their promising dielectric properties.

From Nature to Technology: Exploring the Potential of Plant-Based Materials and Modified Plants in Biomimetics, Bionics, and Green Innovations

This review explores the extensive applications of plants in areas of biomimetics and bioinspiration, highlighting their role in developing sustainable solutions across various fields such as medicine, materials science, and environmental technology. Plants not only serve essential ecological functions but also provide a rich source of inspiration for innovations in green nanotechnology, biomedicine, and architecture. In the past decade, the focus has shifted towards utilizing plant-based and vegetal waste materials in creating eco-friendly and cost-effective materials with remarkable properties. These materials are employed in making advancements in drug delivery, environmental remediation, and the production of renewable energy. Specifically, the review discusses the use of (nano)bionic plants capable of detecting explosives and environmental contaminants, underscoring their potential in improving quality of life and even in lifesaving applications. The work also refers to the architectural inspirations drawn from the plant world to develop novel design concepts that are both functional and aesthetic. It elaborates on how engineered plants and vegetal waste have been transformed into value-added materials through innovative applications, especially highlighting their roles in wastewater treatment and as electronic components. Moreover, the integration of plants in the synthesis of biocompatible materials for medical applications such as tissue engineering scaffolds and artificial muscles demonstrates their versatility and capacity to replace more traditional synthetic materials, aligning with global sustainability goals. This paper provides a comprehensive overview of the current and potential uses of living plants in technological advancements, advocating for a deeper exploration of vegetal materials to address pressing environmental and technological challenges.

Hydrothermally synthesized biofunctional ceria nanoparticles using orange peel extract: optimization, characterization, and antibacterial and antioxidant properties

In this research, cerium oxide nanoparticles were synthesized using orange peel extract via a hydrothermal method. An equal ratio of orange peel extract to cerium nitrate salt led to the formation of cerium hydroxide carbonate, whereas a 1 : 10 ratio formed cerium oxide. The hydrothermal treatment was conducted for durations of 5 and 25 hours. Scanning electron microscopy (SEM) images revealed that the hydrothermal samples treated for 5 hours exhibited significant agglomeration in both extract to salt ratios after heat treatment. X-ray diffraction patterns confirmed that all samples were converted into cerium oxide after heating at 500 °C for 3 hours. Based on XRD and SEM results, three cerium oxide samples, including those synthesized through the 25 hours hydrothermal process with a 1 : 10 ratio and the 25 hours hydrothermal process with both ratios and subsequent heat treatment, were selected for further investigation. Fourier transform infrared (FT-IR) analysis revealed more adsorption of the functional groups of orange peel extract on the surface of the as-synthesized sample. Moreover, the heat-treated sample with a 1 : 10 ratio, initially cerium oxide, displayed a higher amount of surface functional groups than the one with a 1 : 1 ratio which was initially cerium hydroxide carbonate. The antibacterial activities of the samples were determined using the colony count method. Activities of all samples against Gram-negative bacteria are in the range of 91.5-93.2% with a negligible difference, whereas the as-synthesized sample exhibited a superior activity of 96.6 ± 1.8% against Gram-positive bacteria compared to the other two heat-treated samples. The 87.3% antioxidant activity of the as-synthesized sample significantly surpassed that of the other two samples, as evaluated by the DPPH radical scavenging method.