No abstract

A novel biogenic-deposition-precipitation (BDP) approach has been presented for the preparation of stable binary composites using fennel seed extract.

The significant antibacterial activity of silver nanoparticles draws the major attention toward the present nanobiotechnology. Also, the use of plant material for the synthesis of metal nanoparticles is considered as a green technology. In this context, a non-toxic, eco-friendly, and cost-effective method has been developed for the synthesis of silver nanoparticles using seed extract of mung beans (Vigna radiata). The synthesized nanoparticles have been characterized by UV-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). The UV-visible spectrum showed an absorption peak at around 440 nm. The different types of phytochemicals present in the seed extract synergistically reduce the Ag metal ions, as each phytochemical is unique in terms of its structure and antioxidant function. The colloidal silver nanoparticles were observed to be highly stable, even after 5 months. XRD analysis showed that the silver nanoparticles are crystalline in nature with face-centered cubic geometry and the TEM micrographs showed spherical particles with an average size of 18 nm. Further, the antibacterial activity of silver nanoparticles was evaluated by well-diffusion method and it was observed that the biogenic silver nanoparticles have an effective antibacterial activity against Escherichia coli and Staphylococcus aureus. The outcome of this study could be useful for nanotechnologybased biomedical applications.

A simple, ecofriendly, and biomimetic approach using cumin seeds extract (CSE) was developed for the formation of Au-ZnO Schottky contact without employing any chemical capping agents or stabilizers. The various unique phytoconstituents available in cumin seeds extract synergistically convert Au3+ ions into Au0 on the surface of ZnO, as each phytoconstituent is unique in context to its molecular structure and properties. The as-prepared biogenic Au-ZnO hybrid composites were examined using various spectroscopic and microscopic techniques. The TEM investigation and XRD patterns clearly depict the well dispersed AuNPs with the size range 10–15 nm and face centered cubic lattice on wurtzite ZnO nanostructures. The optical study of the nanocomposites showed two absorption bands: one intense band around 390 nm, which corresponds to ZnO, and a second broad band approximately around 540 nm, which corresponds to Au. The photocatalytic efficacy of Au-ZnO nanocatalysts was investigated by observing the mineralization of an aqueous solution of methylene blue (MB) dye under a 200 W tungsten filament lamp as visible light source. The apparent rate constants were also calculated for degradation processes, and it has been observed that 1 and 3 wt % Au-ZnO nanocomposites respectively have 2.27 and 3.2 times higher photoactivity, compared to pure ZnO. This enhanced photoactivity of biogenic Au-ZnO composite materials was resultant from formation of stable and effective Schottky contact between Au metal and ZnO surfaces.

A facile biomimetic approach for the synthesis of gold nanoparticles (AuNPs) using aqueous extract of fennel (Foeniculum vulgare) seeds have been reported in this article. The seeds of F. vulgare are rich in various plant secondary metabolites (phytochemicals) such as polyphenolic acids, flavonoids, and saponins. The phytochemicals of F. vulgare seeds play dual role of reducing and stabilizing agents. The formation of gold nanoparticles was evidenced from the appearance of intense purple color at room temperature with k max around 550 nm in the UV-Vis absorption spectra. The stable AuNPs were further characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) analysis. The synthesized nanoparticles were observed to be polydispersed, spherical and ranged from 10 to 30 nm with an average size of 20 ± 2 nm, as obtained from TEM images. The catalytic activity of gold nanoparticles was investigated by studying the reduction of anthropogenic dyes such as methylene blue (MB) and rhodamine B (Rh-B) with sodium borohydride. Results showed the possible applications of biogenic AuNPs in environment related problems.