A method of synthesizing of gold-silver core-shell nanoparticles, from a colloidal aqueous solution of gold seeds with surfactant, the gold-silver core-shell nanoparticles being produced from anisotropic gold seeds, said method comprising adding to the colloidal aqueous solution a precursor of silver and a reducing agent, to produce the deposition of silver on the gold seeds in a step called principal, characterized in that the method has an incubation step of the colloidal aqueous solution containing the gold seeds with surfactant in the DMSO, prior to the principal step.