Síntese verde de nanopartículas de prata com extrato aquoso de Calendula officinalis e diodos emissores de luz (LED)

Abstract

Green synthesis is a safe, environmentally friendly and sustainable alternative to produce less toxic metallic nanoparticles, more tolerable to the human body, presenting improved biological effects and minimal environmental impact. The use of plants for this purpose has been widely studied, however, there are few studies that attempt to use Light Emitting Diodes (LED) alone or associated with plants.Thus, the aim of this work was to synthesize and characterize silver nanoparticles (AgNPs) obtained by green routes, using aqueous extract of Calendula officinalis flowers with and without photoreduction by LED in different wavelength. It was determined yet, the ideal time to complete silver reduction, and morphological, surface and spectroscopic characterization was performed. The results indicated that the ideal conditions to complete reduction of ion Ag+ to Ag0 were: use of aqueous extract of Calendula oficinallis obtained by infusion of flowers, in proportion of 1/20 to AgNO3 solution, and 48 hours of reaction. It was showed that, the exposition of AgNO3 solution to LED alone, was not cappable to produce AgNPs. However, when associated to the extract of Calendula oficinallis the exposition to LED promoted photochemestry effect, that determined the shape of AgNPs. It was observed by SEM-FEG that AgNPs obteined by extrat of Calendula officinalis presented spherical shape, but AgNPs irradiated by green and blue LED showed It was observed by SEM-FEG that AgNPs obtained just by use of the extract of Calendula officinalis presented spherical shape, however, AgNPs that were irradiated by green and blue LED showed different geometries, as prismatic, cubic and cylindrical. Red LED didn’t promoted changes in the spherical shape os AgNPs. The presence of silver (Ag0 ) in the AgNPs was confirmed by EDS and presence of cristalinity peak at DRX, that was related to metallic silve. Chemical componds of Calendula officinalis on the AgNPs surface were identified by specific bands in the FT-IR and by improve of intensity of light scattering showed in Raman sapctroscopy. It was possible to conclude that aqueous extract of Calendula officinalis 5% flowers is an excelent alternative to green synthesis of AgNps and that LED exposition associated to extract of Calendula officinalis promoted photochemical effects, determining AgNPs shape.