Síntese verde, caracterização e atividade catalítica de nanopartículas de ouro produzidas por extrato de semente de Eugenia uniflora L.

Abstract

In line with the ecologically friendly search for better properties, performance, and obtainment of nanomaterials, this work demonstrates the use of the aqueous extract of Eugenia uniflora L. (brazilian cherry) seeds as a reducing agent in the green synthesis of gold nanoparticles (AuNPs) and their potential catalytic activity. This nanomaterial was produced using tetrachloroauric acid (HAuCl4) as a precursor in a single-step route. The characterization of the obtained AuNPs was performed by Ultraviolet-Visible spectroscopy (UV-Vis), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Also, catalytic effect applications of the produced AuNPs were tested to reduce the cationic dyes Methylene blue (MB) and Toluidine blue (TB), critically contaminating organic compounds. UV-Vis spectroscopy analysis showed a characteristic surface plasmon resonance (SPR) absorption peak with max centered at 537 nm, confirming the satisfactory formation of AuNPs. The produced AuNPs showed good stability, with no aggregation occurring for at least two months. The FTIR ATR analysis showed several absorption bands between 815 cm-1 and 3240 cm-1 , confirming the existence of biomolecules containing OH, NH, C=ONH2, COC, COOH, C=O, and C=CH2 groups in the content of the aqueous extract of Eugenia uniflora L. seeds, which are associated with the reduction of Au3+ ion as well as the capping and stabilization of the AuNPs. XRD measurements confirmed the crystallinity of the AuNPs, and the calculated average crystallite size was 11 nm. TEM analysis confirmed that the AuNPs exhibit varied geometric shapes, such as spherical and triangular, with an average particle diameter of 18 nm. Finally, an applied catalytic study demonstrated that AuNPs exhibit catalytic activity. The reduction of MB with AuNPs in the presence of NaBH4 at room temperature occurred in 14 min of reaction, with a percentage reduction of MB (0.05 M) of 99%, and, with the same technique, a reduction was observed catalytic reaction of 81,2% of the TB (0.05 M) in 7 min of reaction, confirming the catalytic potential for the synthesized AuNPs.