Large-scale orientation dependent heating from a single irradiated gold nanorod.

We quantify the extreme heating associated with resonant irradiation of individual gold nanorods by using a novel assay based on partitioning of lipophilic dyes between membrane phases. The temperature increase is sensitively dependent on the angle between the laser polarization and the orientation of the nanorod. A dramatic and irreversible decrease in the heating of a nanorod occurs at high-illumination intensities; this effect is attributed to surface melting of the nanorod causing it to restructure into a more spherical shape and lose its extreme photothermal properties.