Coinage metals nanoparticles have been widely used in last decade for enhancing the Raman signal of a variety of compounds. Several preparation methods have been proposed, including chemical reduction of gold or silver salts with sodium citrate, hydroxylamine or sodium borohydride, microwave-assisted reduction with glucose, Tollens mirror, electrodeposition, vacuum evaporation and pulsed-laser deposition.
In this work, gold and silver nanoparticles were prepared by chemical reduction with sodium citrate and hydroxilmanine, characterized by UV-Vis spectroscopy and High Resolution Transmission Electronic Microscopy and tested as SERS substrate. Carminic acid, cochineal, axiote, muitle and zacatlaxcalli SERS spectra were recorded at different pH. Natural dyes samples were prepared by extraction from its natural sources, following traditional recipes. Although differs for each dye, best results were achieved by performing SERS experiments at pH neutral to basic.