Green Synthesis of Gold Nanoparticles Obtained from AlgaeSargassum cymosum: Optimization, Characterization and Stability

摘要

Gold nanoparticles (Au-NPs) were synthesized by a green synthesis approach using the extract of the algaeSargassum cymosum. The synthesis was carried out with different extracts and tetrachloroauric acid concentrations, temperature, pH, and stirring rate. For all the experiments, the formation of gold nanoparticles was noticed by the color change of the reaction medium after few minutes and by UV-Vis spectrophotometry and dynamic light scattering (DLS) measurements, which confirmed the formation of Au-NPs with an average size mostly between 5 and 22 nm depending on the experimental conditions. The algae extract to metal precursor mass ratio, reaction temperature, as well as the pH have important influence in the yield and stability of the nanoparticles, while the stirring rates tested (300-1000 rpm) did not influence the results to a significant extent. Transmission electron microscopy (TEM) analyses of three samples showed the predominance of nanoparticles with spherical shape and average size between 7 and 20 nm. The storage effect upon the Au-NPs was evaluated by UV-Vis spectrophotometry for a selected number of samples and indicated adequate stability of the materials up to 4 weeks after the synthesis, with the formation of small aggregates. After a storage period of 9 months, it was verified by TEM that six samples remained stable, leveraging possible commercial applications for the Au-NPs produced.