Core-shell nanoparticles based on Ag-Au nanoshell core and mesoporous silica shell with a radial pore orientation have been synthesized using a sol-gel surfactant templating method. The Ag/Au ratio of the nanoshells were elaborated through a galvanic replacement method performed with hydroxide gold substituted precursor using HAuCl4 as native gold precursor and NaOH as modifier. The nanoshell synthesis was optimized to provide light absorption in the near infrared "biological window" region before silica coating.