Synthesis of Gold Nanospheres - Reduced By CdSe QDs: New SERS Substrates For Biomolecules Detection

Surface-Enhanced Raman Spectroscopy (SERS) is a potent spectroscopic technique for detecting very low concentrations of analytes. By using SERS, the intensity can be enhanced by a factor of 10⁶ to 10¹¹ or higher, under well controlled conditions. Gold Nanospheres (Au NPs) are commonly used as SERS active substrates. These NPs can be synthetized using sodium borohydride, sodium citrate and hydrolamine as reducing agents. By looking for new ways to synthetize, in this investigation a new synthesis for Au NPs was proposed using cadmium selenide as a reducing agent. A solution of 0.01M of hydrogen tetrachloroaurate (III) hydrate (HAuCl₄ 3H₂O) was reduced in 40mL of water using a very small amount of CdSe quantum dots (CdSe QDs) solution in a very short time. These NPs were characterized by UV-Visible Spectroscopy, X-Ray Difraction (XRD) and transmission electron microscopy (TEM). NPs showed a very sharp absorption peak at 535nm indicating well monodispersed NPs. These NPs were very sensitive detecting a small concentration of adenine as a test biomolecule in solution and solid deposited NPs. The most intense peak of adenine was observed at 738cm^-1 Raman shift due to ring breathing. These results demonstrated that the new synthesis can be used for biosensing applications using SERS.