"Síntese NINA: uma estratégia para produção de nanobastões de ouro em larga escala a partir do método mediado por semente assistido por íons prata"

Abstract

The importance of gold nanorods (Au-NBs) is due to their optical, catalytic, photothermal properties, and their varied applications, with emphasis on biomedical applications. In this way, the present work aims to obtain uniform Au-NBs, in sufficient quantity to advance in several stages of application research, which is still a current challenge. A strategy for large-scale production of Au-NBs was proposed from Nikoobakht and El Sayed's (2003) silver-assisted seed-mediated synthesis, as well as the characterization of the surface of Au-NBs, via photoelectron spectroscopy of X-rays, to contribute to the understanding of the role of chemical species on the surface of these nanomaterials. The large-scale synthesis, named NINA, was carried out in five steps. The Au-NBs obtained were characterized using the techniques of transmission electron microscopy (TEM), electron spectroscopy in the ultraviolet and visible region (UV-Vis), XPS. As main results, the production of gold nanorods in an amount 100 times greater than that obtained by the classical synthesis method of Nikoobakht and El Sayed (2003) stands out. Relative standard deviations (σ) from the maximum of the highest intensity plasmonic band were calculated for the replicates of the original synthesis (σ=19.5) and for fractions of the NINA synthesis (σ=9.4), and a comparison was made between these data. The values of σ indicated less dispersion for the NINA fractions than for the replicates of the original synthesis, from these and other data, it was possible to infer about the viability of the NINA synthesis. A projection was proposed for the production, via NINA synthesis, of at least 800 times more Au-NBs than the classical synthesis. From the XPS data, a better understanding was obtained about the chemical state of the substances present on the surface of Au-NBs, highlighting that among the substances, silver was found in two Ag(0) oxidation states (368.2 and 374.3 eV) and Ag(I) (367.4 and 373.4 eV), and these findings contribute to the understanding of the formation mechanism of Au-NBs.