Absorption spectroscopy and identification of single metal nanoparticles

Optical absorption spectroscopy of a single nanoparticle is performed using a spatial-modulation microscope combined with a white-light supercontinuum source. The absolute values of the extinction cross-section of isolated 16nm size gold nanoparticles are determined around their surface plasmon resonance. Measurements performed as a function of the linear light polarization permit to optically identify the properties of an individual particle: size, shape and orientation on the substrate. The statistics of this optically deduced properties are found in excellent agreement with those obtained with transmission electron microscopy.