The effect of inserted gold nanosphere on the local field enhancement of gold nanoshell

Because of the hybridized coupling between the bonding shell plasmon and the inserted sphere plasmon, there are two major peaks in the local field enhancement spectra of gold–dielectric–gold multi-nanoshells. The inserted gold nanosphere takes great effect on the local electric field enhancement at different interfaces and locations of this multilayer core–shell nanostructure. In the case with small thickness of the outer gold shell, the interaction between the inner and outer surface of the gold shell is intense. Increasing radius of the inserted gold sphere always leads to the longer wavelength peak red shift and the shorter wavelength peak blue shift. However, the way the local field intensity changes as a function of inserted gold sphere size is different at different location. In the case with large thickness of the outer gold shell, the interaction between inserted gold sphere and inner surface of the gold shell takes major effect and greatly depends on the radius of the inserted gold sphere. Thus the effects of inserted gold sphere on the local field enhancement are different from the case with thin gold shell. Blend and split of local field enhancement peaks take place in this case when the size of inserted gold sphere is changed.