Broadband light absorption by silver nanoparticle decorated silica nanospheres

Plasmon enhanced light harvesting using silver nanoparticle (Ag NPs) decorated SiO2 nanospheres (NSs) provides an effective key to tuning plasmonic properties. The SiO2 NS plays a vital role in controlling the separation distance between Ag NPs and the optical interactions. Closely packed Ag NPs localize the electric field in between the NPs and create a hot spot due to the high energy dissipation. In this work, a systematic study identified the critical role of the synthesis parameters such as SiO2 surface modification, and the synthesis route on the decoration of Ag NPs on SiO2 NSs. The radii of SiO2 NSs has been controlled in the range of 25 to 55 nm by using a mixture of methanol and ethanol. Depending on the synthesis route, the average radii of the decorated Ag NPs are 3 to 6 nm and the average number of Ag NPs per SiO2 NS is about 16 to 180. 3D-FDTD modeling is used to calculate the optical extinction properties of Ag NP decorated SiO2 NSs. It is demonstrated that the surface plasmon resonance (SPR) peak properties are dependent on the filling fraction, SiO2 core radius, and the synthesis route. Using Co2+ in the decoration of SiO2 NSs provided a ring like structure and showed superior plasmon characteristics such as broader spectral line width, and the red shift of the peak position. The tunability of plasmon resonance bands has been highlighted theoretically and experimentally and may have benefits in solar harvesting devices such as volumetric solar receiver, photocatalysis, surface enhanced Raman scattering.