Green Synthesis of Silver Nanoparticles from Natural Compounds: Glucose, Eugenol and Thymol

Abstract

Currently, renewable energy, clean technology, recycling and green synthesis are the main fields of researchers who are interested in saving our planet. The work is mainly aimed at the use of phytochemical compounds of high purity to prepare silver nanoparticles. These compounds work as a reducing agent of aqueous silver nitrate to define the most appropriate compounds which are in charge of this chemical reaction. The compounds (eugenol, D-glucose, coumarin, thymol, sucrose, scopolamine, L-asorbic, khelin, and citric acid) are separately added to 1m M AgNO3 at various pH. Only the first three compounds exhibited a significant color change to dark brown or gray as reduction indicators. UV-visible spectroscopy was utilized as a preliminary investigation of AgNP formation during the experiments. Morphology, elemental analysis and crystallinity were investigated with SEM, EDS, particle size analysis and XRD. The UV-visible spectra revealed a characteristic band at 400-450 nm. The spherical shape of the silver nanoparticles derived from all natural compounds was observed by scanning electron microscopy. The NPs synthesized in glucose solution had an average size that varied from 30 to 80 nm and contained a large portion of NP aggregates, those in eugenol solution had an average size of 150 nm, and those in thymol solution had an average size of 230 nm and contained a small portion of NP aggregates. A higher yield of NPs resulted in increased pH and concentration in a richer ion solution and more alkaline medium, respectively, due to the increased reducing power of the compound; however, this was not seen for the eugenol agent, which did not exhibit a significant effect of pH.