Gold nanoshells (Au@SiO₂) and silica-covered gold nanoshells (SiO₂@Au@SiO₂) were fabricated by self-assembly and colloid reduction chem-istry. Hollow silica shells with movable silica spheres (H-SiO₂@M-SiO₂) were also prepared by the dissolution of gold shells within SiO₂@Au@SiO₂ particles. The results show that silica-covered gold nanoshells preserve the near-infrared absorbance of gold nanoshells. The plasmon resonance peaks of the resulting SiO₂@Au@SiO₂ could be controlled by changing the thickness of the outer silica shells. Furthermore, the gold shells within SiO₂@Au@SiO₂ particles could be removed by using aqua regia, and the related plasmon resonance peaks disappeared.

Key words: core-shell structure, gold nanoshell, silica-covered gold nanoshell, plasmon resonance, refractive index