Desenvolvimento de um sistema contendo nanopartículas de ouro dispersas em material graxo e sua aplicação em espectroscopia raman intensificada por superfícies (SERS) para avaliação de moléculas orgânicas sulfuradas

Abstract

In this study, we used anisotropic gold nanoparticles (AuNPs) dispersed in castor oil and immobilized in hydrogenated castor oil, for the construction of a material to be used in Surface Enhanced Raman Spectroscopy (SERS-active substrate). The AuNPs synthesized were characterized by absorption spectroscopy in the Ultraviolet-visible region (UV-vis), where it was possible to observe a displacement of the absorption band after preparation of the substrate, from 650 to 690 nm, and by Transmission Electron Microscopy (TEM), which showed obtaining AuNPs with star shape and average size of 100 nm. To investigate the potential SERS applications, the obtained substrates were tested using the sulfur molecules of 4-aminothiophenol (4-ATP), benzothiophene (BTF), thiophene (TF), cysteamine and cysteine as probe molecules. The SERS spectra were obtained by analyzing the substrate after the immersion, for 24 h, in solutions with different concentrations of probe molecules. Using 4-ATP as a probe molecule it was possible to obtain SERS spectra with a concentration range of 2,88x10-2 to 1x10-10 mol L-1, with BTF and TF it was possible to increase its Raman bands from 1x10-1 to 1x10-6 mol L-1. Cysteamine and cysteine were also used as probe molecules, but with only one concentration, 1x10-1 and 5x10-2 mol L-1, respectively. The results showed that the developed material has interesting sites with SERS activity, allowing us to study its interaction with different probe molecules, so it can be applied to different areas, both in qualitative and quantitative analysis, even for molecules in solutions with very small concentrations. The obtained substrate presented EF of the order of 102 to 103.