Observation of plasmon line broadening in single gold nanorods

Attempts to realize the important potential of gold nanorods as extremely bright molecular markers have been limited by the broad spectroscopic linewidths usually observed. We identify the origin of this broadening as inhomogeneous broadening due to the extreme sensitivity of the surface plasmon resonance to the nanorod aspect ratio. Using confocal light scattering spectroscopic microscopy, we observed the narrow homogeneously broadened plasmon lines of single gold nanorods and obtained the first quantitative measurements of this homogeneous broadening. We show that homogeneous broadening can be predicted from first principals.