Abstract
Metallic nanoparticles, due to their reduced size and high surface area, have unique properties that facilitate their application, with excellent results, in various scientific fields and allows an easy functionalization of their surface with a variety of ligands. Noble metallic nanoparticles play a special role in nanomedicine due to their proved antibacterial, antifungal and strong antioxidant activity. These metallic nanoparticles can be prepared using both conventional and unconventional routes and, in the last decades, the methods involving plants and their aqueous extracts are constantly and successfully replacing expensive and time - consuming conventional chemical methods. This paper describes the one - pot green synthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) from aqueous plant extracts and corresponding metallic salts under different time and temperature conditions. Both silver and gold nanoparticles are green synthesized from plants with important pharmacological benefits to human health: Hyssopus (Hyssopus officinalis), European goldenrod (Solidago virgaurea) and Knotgrass (Polygonum aviculare) and their synthesis is monitored by recording the UV - Vis spectra at specific time intervals: 0s, 5 min, 15 min, 30 min, 1 hour and 24 hours in order to evaluate their stability in time. FTIR spectra were used for the specific determination of functional groups and DLS was used to determine the nanometer scale of the particles. Also, antioxidant activity was evaluated using the DPPH method for both silver and gold nanoparticles and compared to that of the crude aqueous extracts.
Highlights
Nanotechnology is constantly and rapidly detaching as one of the most promising technologies that allows numerous applications in various areas of material science
Antioxidant activity for Hyssop (Hyssopus officinalis), European goldenrod (Solidago virgaurea) and Knotgrass (Polygonum aviculare) aqueous extract, AgNPs and AuNPs was evaluated using the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate stable free radical) method: a DPPH solution was prepared in ethanol and 0.5 mL aqueous plant extract was mixed with 1 mL 0.02 mg/mL DPPH solution
For all the green synthesized AgNPs, AA (%) has increased values that those of the corresponding aqueous extracts and a comparison between AgNPs and AuNPs highlights that the antioxidant activities for all the green synthesized AgNPs are higher compared to AuNPs (Table 6)
Summary
Nanotechnology is constantly and rapidly detaching as one of the most promising technologies that allows numerous applications in various areas of material science. In the last two decades, noble metallic nanoparticles, especially silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) have received worldwide attention due to their numerous applications in the biomedical and physiochemical fields [1]. Synthesizing AgNPs and AuNPs using microorganisms and especially different plants and plant parts (e.g.,: stem, bark, seeds, flowers, etc.) has been extensively studied and has, been recognized as an efficient alternative route that properly allows obtaining affordable and reproductible noble metallic nanoparticles [2]. Green synthesis of noble metallic nanoparticles, especially plant-mediated one, is a cheap, facile and environmentally friendly approach. Does it eliminate the use of hazardous chemicals and allows an active coating of biological moieties on the surface of the metallic nanoparticles [5]. A very important characteristic is that all the phytocompounds play a major part in the reduction and stabilization of the one-pot green synthesized noble metallic nanoparticles
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