Insight into the localized surface plasmon resonance property of core-satellite nanostructures: Theoretical prediction and experimental validation.

Regulation of the localized surface plasmon resonance (LSPR) of nanoparticles by changing the dielectric constant of the surrounding medium has been exploited in many practical applications. In this study, using Ag-nanodot-decorated SiO2 nanoparticles (Ag-decorated SiO2NPs) with different solvents, we investigated the potential of using such core-satellite nanostructures as a liquid sensor for the determination of melamine. The dielectric constant effect of the surrounding medium on the LSPR property was given particular attention. It was found that colloids with water as solvent display a LSPR shift of 14nm, and this value was 18nm for ethanol. For colloids with methanol and glycol as solvents, the peak shifts are negligible. Finite-difference time-domain (FDTD) simulations were used to assign the LSPR peaks of Ag-decorated SiO2NPs and to monitor the effect of the substrate and solvent on the LSPR properties. In the calculations, the wavelength positions of the LSPR peaks for Ag-decorated SiO2NPs in various solvents were successfully predicted in the order methanol<water<ethanol<glycol, as also verified by experiments. The separation distance of Ag nanodots and their relative positions on the SiO2 substrate with respect to the incident light were also found to be crucial to the characteristic LSPR peak positions. The LSPR peak undergoes a shift in the presence of different concentrations of melamine. We proposed a multi-mode absorption model to describe the effect of melamine absorption on the LSPR peak shifts of Ag-decorated SiO2NPs. Based on this model, we were able to quantitatively explain the LSPR peak shift of Ag-decorated SiO2NPs in the presence of various concentrations of melamine. Our work is expected to be valuable for theoretical guidance in design of new materials and devices based on LSPR effects.