Synthesis and studies of spindle-shaped lead selenide nanocrystals

Spindle-shaped lead selenide (PbSe) nanocrystals were synthesized by solution processing synthetic method for the first time. The prepared PbSe nanocrystals were characterized by X-ray diffraction, transmission electron microscopy and near-infrared absorption spectroscopy. X-ray diffraction pattern shows that the synthesized PbSe nanocrystals have cubic rock salt structure. Spindle-shaped PbSe nanocrystals are formed by spontaneous alignment and fusion of small quasi-spherical PbSe nanoparticles, namely, oriented attachment. It is believed that the relative strength between steric hindrance force caused by capping molecules and orientation force caused by the dipole moment determined the growth process and final morphologies of nanocrystals. If the orientation force along some axes can overcome the steric hindrance force, the small PbSe nanocrystals with certain size distribution will self-assemble and evolve to spindle-shaped PbSe nanocrystals. If not, the small PbSe nanocrystals will grow individually to bigger quasi-spherical PbSe nanocrystals. Four discrete absorption peaks appear in the near-infrared absorption spectrum of synthesized PbSe nanocrystals due to the quantum confinement effects.