SiO2–Au core–shell petal-like structure with controlled bridge length

Metal nanoshell/dielectric core structures with complicated morphology, such as a nano-petal-like structure, were fabricated by controlling the sintering and etching of colloidal crystal structures. The two-step sintering (TSS) process successfully suppressed the movement of SiO2 particles on a quartz substrate during the thermal sintering. The diffusion of atoms on the particle surface was promoted by TSS method, as a result, the mass density at the bridge region was increased. As the subsequent HF etching treatment, the TSS structures showed different morphology from the etched general (one-step) sintered structures. The structural dependence of position and intensity of the plasmon resonance peak was observed. These optical phenomena were discussed from the viewpoint of domain size, particle shapes and nanogaps.