Biosynthesizing of silver nanoparticles using microorganisms or various plant parts have proven more environmental friendly, cost-effective, energy saving and reproducible when compared to chemical and physical methods. This investigation demonstrated the plant-mediated synthesis of silver nanoparticles using the aqueous leaf extract of Thevetia peruviana. UV-Visible spectrophotometer was used to measure the surface plasmon resonance of the nanoparticles at 460 nm. Fourier Transform Infrared showed that the glycosidic -OH and carbonyl functional group present in extract were responsible for the reduction and stabilization of the silver nanoparticles. X ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and Selected Area Electron Diffraction analyses were used to confirm the nature, morphology and shape of the nanoparticles. The silver nanoparticles are spherical in shape with average size of 18.1 nm. The synthesized silver nanoparticles showed activity against fungal pathogens and bacteria. The zone of inhibition observed in the antimicrobial study ranged between 10 and 20 mm.

No abstract

No abstract

In this report, synthesis, growth and formation kinetics of silver nanoparticles mediated by various plant extracts in their biodiversity have been monitored using UV-Vis spectrophotometer by sampling at time intervals during bioreduction process. Plasmon band resonance of the silver nanoparticles was observed as the reaction progresses indicating nucleation and particle formation. There were cases of red shifting indicating particle size increase. In the bioreduction process, onset of nanoparticle nucleation and growth were observed within 2, 5, 10 or 30 min and eventual formation of spherical or quazi-spherical amidst twinned morphology as determined by transmission electron microscope (TEM). The nanosilver growth kinetics mechanism has been probed using a time-resolved UV-Vis in conjunction with TEM following existing Lifshitz-Slyozov-Wagner theory. For some biological extractmediated synthesis, a single-stage mechanism that is diffusion controlled following Ostwald ripening (OR) is proposed. Whereas, for other bioreduction process, a double stage involving (1) initial OR followed by (2) surface adsorption-oriented attachment is proposed for temporal evolution of the nanosilver in green environment.

This study emphasizes the production of eco-friendly silver nanoparticles from a medicinal plant extract of Morinda lucida (M. lucida) and investigated its antioxidant and antimicrobial activity. Phytochemical screening of M. lucida (ML) leave extract was carried out and observed to contain some fundamental phyto-reducing agents such as reducing sugar, proteins, and alkaloids. The green synthesized AgNPs (ML-AgNPs) were characterized by UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission emission microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Energy dispersive X-ray analysis (EDX). Thermo gravimetric analysis (TGA) was performed on the synthesized ML-capped AgNPs to determine the thermal stability and the formation of the green synthesized AgNPs. The formation of AgNPs was confirmed by the UV–vis absorption spectra, which showed an absorption band at 420 nm. The morphology of ML extract-mediated AgNPs was mostly spherical and rough-edged crystallite nanostructures, with an average particle size of 11 nm. The FTIR analyses revealed distinctive functional groups which were directly involved in the synthesis and stability of AgNPs. The crystallite size was 8.79 nm, with four intense peaks at 2 θ angles of 38°, 44°, 64°, and 77°. At an energy level of 3.4 keV, a significant signal was observed indicating the production of thermally stable and pure crystallite AgNPs. The antioxidant property of green synthesized ML-AgNPs was determined to be 40% higher than that of crude M. lucida leaf extract. The ability of green synthesized ML-AgNPs to scavenge free radicals also increased in the order of OH − < NO < H 2 O 2 . The ML-AgNPs have strong activities with a maximum against P. vulgaris and a minimum with E. faecalis.