Charge-induced Rayleigh instabilities in small gold rods.

It is demonstrated that the addition of electrons to gold nanorods with aspect ratios ranging from 2 to 4 leads to an initial blue-shift in the absorption spectrum due to the increasing surface plasmon frequency of the electron gas. However, at longer times, there are changes in particle morphology induced by the surface charge. In the case of smaller injected electron densities, the surface plasmon band red-shifts as the end caps of the rods undergo increased faceting and develop {111} faces. In the case of higher electron densities, the rods undergo fragmentation into clouds of smaller spheres. These secondary processes and fragmentation are postulated to be a direct result of crossing the Rayleigh threshold.