The roles of green chemistry in nanotechnology and nanoscience fields are very significant in the synthesis of diverse nanomaterials. Herein, we report a green chemistry method for synthesized colloidal silver nanoparticles (Ag NPs) in polymeric media. The colloidal Ag NPs were synthesized in an aqueous solution using silver nitrate, polyethylene glycol (PEG), and β-d-glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag NPs were studied at different reaction times. The ultraviolet-visible spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM) and their size distributions. The Ag NPs were characterized by utilizing X-ray diffraction (XRD), zeta potential measurements and Fourier transform infrared (FT-IR). The use of green chemistry reagents, such as glucose, provides green and economic features to this work.

Since two decades ago, the concept of green chemistry has been spreading and researchers are developing greener and more sustainable methods for nanoparticles (NPs) production. The main goals are fabrication of NPs with cost-effective and straightforward methods while eliminating the use of hazardous chemicals, which are commonly used as reducing or capping agents. In this regard, many bio-sources such as fungi, yeasts, algae, bacteria, and plants have been exploited to fabricate NPs in different shape and size. In this review, authors have focused on the most recent studies for fabricating silver NPs using bio-sources with an emphasis on the role of medicinal plants. The possible applications of biosynthesized silver NPs as well as their antibacterial, cytotoxic, and antioxidant activities are also addressed and discussed. Finally, future aspects and current limitations for bio-synthesized AgNPs are mentioned.

In this study, we investigated the synthesis of silver nanoparticles using Peganum harmala water extract at ambient temperature. The Ag nanoparticles (AgNPs) were characterized by ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT–IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The average particle size of the silver nanoparticles was about 23 nm. Inhibitory activity of the synthesized AgNPs was tested against human pathogens like Escherichia coli and Staphylococcus aureus. The results indicated that the AgNPs showed moderate inhibitory actions, demonstrating its antibacterial value against pathogenic diseases. GRAPHICAL ABSTRACT

The aqueous extract of Tarragon, as a reducing agent, was used to synthesize silver–montmorillonite (MMT) nanocomposite (Ag–MMT-NPs) in the batch method. The leaf extract and metal solution concentrations were optimized to improve Ag–MMT-NPs synthesis in 48 h. For characterizing the nanocomposite, powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and UV–Vis spectroscopy were performed. The peak was observed at 437 nm on the UV–Vis spectrum, showing the surface plasmon resonance of Ag–MMT-NPs. Using XRD analysis, the crystalline nature and purity of Ag–MMT-NPs were confirmed. FTIR was used to evaluate specific functional groups, causing a reduction in silver nitrate during Ag–MMT-NPs formation. According to TEM, the average particle size was 25.12 nm in AgNPs. The nanocomposite showed antibacterial properties against Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus aureus).

The aqueous extract of Adiantum capillus-veneris L was used as a reducing agent in the batch method for the synthesis of silver nanoparticles (AgNPs). For improving AgNP synthesis, the concentrations of metal ions solution and leaf extract were optimized in 24 h. Using Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis spectroscopy, AgNPs were characterized. In the UV-Vis spectrum, the peak was observed at 453 nm, indicating the surface plasmon resonance (SPR) of AgNPs. The purity and crystalline nature of AgNPs were confirmed based on the XRD assessment. In addition, specific functional groups, which led to silver nitrate reduction in AgNP formation, were examined using FTIR. According to TEM, the average particle size was 18.4 nm in AgNPs. Antibacterial activity assays with Escherichia coli and Staphylococcus aureus demonstrated that AgNPs reduced bacterial growth and produced well-defined inhibition zones. GRAPHICAL ABSTRACT

In this project, facile, rapid biosynthesis and characterization of silver–montmorillonite (MMT) nanocomposite is carried out at ambient temperature. Silver nanoparticles (Ag-NPs) were prepared by water extract of the plant [Satureja hortensis (L)] as the reducing agent and MMT as interlamellar space for controlling the size of Ag-NPs. MMT was sonicated in the aqueous AgNO₃ solution and Ag⁺ ions were reduced to Ag° using water extract of Satureja hortensis (L). The nanocomposite was evaluated using ultraviolet–visible spectroscopy (UV–Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM study showed the formations of nanocomposite using water extract of Satureja hortensis L in the range of 4.88–26.70 nm and an average particles size of 15.79 nm. In addition, XRD studies indicated that the particles have a face centred cubic (FCC) structure. The nanocomposite showed antibacterial effects against bacteria.