Extracts from vitex, magnolia and camellia leaves as reagents for green synthesis of silver nanoparticles: the degree of precursor conversion into plasmonic particles and the particles dispersity
摘要
Silver nanoparticle (AgNPs) colloids were synthesized by one-pot method using the extracts from the leaves of Vitex agnus-castus, Magnolia kobus, and Camellia japonica as “green” reagents. The synthesis was performed at 25 and 70 °C for up to 7 days to find the conditions that ensure maximum transformation of silver precursor, AgNO3, into plasmonic AgNPs. The maximum yield of plasmonic AgNPs was found to be ~ 80%; this value seems to be considerably higher than those typically reported in the literature on green synthesis of AgNPs. In all cases, a minor fraction of silver precursor was found to be present in the colloids as Ag+ ions and/or very small particles or clusters that do not exhibit clear plasmonic properties. While the reduction of most of the silver precursor was almost completed within a few minutes, at 70 °C the significant increase in plasmon peak intensity occurred during about 5, 15, and 25 h for camellia, magnolia, and vitex extracts, respectively. The percentage and the sizes of resulting plasmonic AgNPs were found to be affected by both the synthesis conditions and the extracts composition. The main components of vitex and magnolia extracts, flavones / flavonols and hydroxycinnamic acids, appeared to be better stabilizing agents than catechins and hydroxybenzoic acids, which dominated in camellia extract.
Graphical Abstract