Shape control of PbS nanocrystals using multiple surfactants.

A novel technique is presented for preparing PbS nanorods with all spatial dimensions comparable to the excitonic Bohr radius of PbS. The shape of the PbS nanocrystals is entirely controlled by using a combination of three different surfactants with different end functional groups. Oleylamine, oleic acid and trioctylphosphine are used to tune the shape of the PbS nanocrystals from cubic, stars, to rods and then to branched nanowires. The PbS nanorods have rock-salt structure with growth along the [220] direction.