Investigation on the Sensitivity and FOM of Ag Nanoparticles and Nanoarrays

The localized surface plasmon resonance (LSPR) spectroscopy of Ag nanoparticles (NPs) is sensitive to the changes of the surrounding medium, which enables the NPs to serve as plasmonic nanosensors. In this paper, the refractive index (RI) sensitivity and figure of merit (FOM) of individual NPs and nanoarrays are investigated by employing the finite difference time domain (FDTD) method. The influence of shape and size are analyzed for individual NPs, and the influence of particle spacing is analyzed for nanoarrays. It is found that the NP with shorter size in incident direction or longer size in polarization direction exhibits better sensing performance. And when the a_eff is between 20 and 60 nm, the larger NP exhibits higher sensitivity but lower FOM. The results of nanoarrays show that when particle spacing is large, the sensitivity of nanoarrays is large, and the sensitivity of nanoarrays decreases first and then increases as particle spacing decreases. In addition, the FOM of nanoarrays exhibits the similar trend.