Rational synthesis, self-assembly, and optical properties of PbS-Au heterogeneous nanostructures via preferential deposition.

High-quality, monodisperse PbS-Au(1), PbS-Au(4), and PbS-Au(n) nanostructures have been synthesized via a facile and convenient solution chemistry approach. HRTEM images of these nanostructures showed good selectivity of gold deposition on the semiconductor in several spatially correlated directions. The formation of these regular nanostructures can be explained by the difference in polarity of crystal facets that led to the selective growth of metal on the semiconductor surface. Owing to their narrow size distribution and intrinsic high-symmetry, the resulting PbS-Au(4) and PbS-Au(n) heterogeneous nanostructures could spontaneously self-assemble into ordered arrays with different symmetries. From the results of the pump-probe measurements, the presence of Au in PbS-Au(4) nanostructures has substantially altered the nonlinear optical response of PbS nanocrystals.