Different Plasmon Sensing Behavior of Silver and Gold Nanorods

Silver nanorods (AgNRs) of ∼20 nm diameter and different lengths, which were increased up to ∼100 nm by increasing the reduction time, were prepared by a seedless synthetic approach. A linear relationship between the AgNRs aspect ratios and the LSPR peak position was observed experimentally and confirmed theoretically. The Raman signal enhancement by silver nanorods is more efficient than by gold nanorods (AuNRs) because the plasmon field intensity of AgNRs is stronger than that of AuNRs, as shown by the discrete dipole approximation calculation. The Rayleigh scattering by AuNRs is stronger than that by the AgNRs. Therefore, AuNRs are recommended for optical plasmon imaging, while AgNRs are more efficient in plasmon sensing.