Optical and morphological properties of Au@Ag core-shell nanoparticles: Influence of different reducing agents

Colloidal suspensions of gold coated with silver core-shell nanoparticles in poly vinyl alcohol were prepared by the seed-mediated growth approach and a comparative study of optical and morphological properties was conducted. Two types of gold seeds were considered. For the first type, a strong reducing agent (NaBH₄) and for the second one, a weak reducing agent (Na₃C₆H₅O₇) were used. Four volumes of AgNO₃ solution were used to obtain silver coatings with different thicknesses. In each case, morphological and optical properties were investigated by transmission electron microscopy and ultraviolet-visible spectroscopy, respectively. Also, numerical calculations of optical absorption were performed with Matlab toolbox for the simulation of metallic nanoparticles, using a boundary element method approach. This study offers practical considerations useful as a route of synthesis at room temperature of this type of nanoparticles, in such a way that a good homogeneity and reproducibility can be achieved. Results here presented show practical details useful in the synthesis of this type of nanoparticles for applications such as catalysis.