CORRELATION BETWEEN STRUCTURAL AND OPTICAL-PROPERTIES OF PBS NANOCRYSTALS

PbS semiconductor nanocrystals have been synthesized in order to study the modifications of their optical properties in relation to their si ze. The synthesis has been carried out by using the techniques of coll oid chemistry. A fast evolution of the optical absorption spectrum has been noticed following synthesis. immediately after the synthesis rea ction, the samples exhibit a structured absorption spectrum with three well-defined excitonic peaks. Within a few minutes, the peaks progres sively disappear and a structureless spectrum occurs. A procedure of s tabilization of the colloids has been set up in order to allow the stu dy of the structural and optical properties at different stages of the ir evolution. Fiber-like nanocrystals (2.5 x 25 nm) and platelets have been found in the early stages of the synthesis and nearly cubic nano crystals (13 nm) are found in later stages of evolution.