Green Synthesis of Gold Nanoparticles Obtained from Algae Sargassum cymosum : Optimization, Characterization and Stabili

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Green Synthesis of Gold Nanoparticles Obtained from Algae Sargassum cymosum: Optimization, Characterization and Stability L. H. Costa 1 & J.V. Hemmer 2 & E. H. Wanderlind 3 & O. M. S. Gerlach 2 & A. L. H. Santos 1 & M. S. Tamanaha 4 & A. Bella-Cruz 2 & R. Corrêa 2 & H. A. G. Bazani 5 & C. M. Radetski 6 & G. I. Almerindo 1,2

# Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Gold nanoparticles (Au-NPs) were synthesized by a green synthesis approach using the extract of the algae Sargassum 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. Keywords Green synthesis . Gold nanoparticles . Algae polysaccharides . Synthesis optimization . Sargassum . Sargassum cymosum . Colloidal stability

1 Introduction Materials at the nanometric scale present distinct properties than those displayed by the corresponding bulk materials, enabling new opportunities for their application in different fields of science, including chemical catalysis and

biomedicine [1–3]. However, top-down or bottom-up methods for the synthesis of metallic nanoparticles sometimes involve toxic compounds and onerous physical processes [4]. Concern about environmental impacts has become an important focus on all scientific research, and attempts have been made to improve synthetic routes for the production of

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12668-020-00776-4) contains supplementary material, which is available to authorized users. * C. M. Radetski [email protected]

3

Institute of Chemistry, University of Campinas (UNICAMP), Campinas, SP 13083-970, Brazil

* G. I. Almerindo [email protected]

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Oceanografia, Laboratório de Ficologia, Universidade do Vale do Itajaí (UNIVALI), Rua Uruguai, 458, Itajaí, SC 88302-901,