Mid-Infrared Emitting Lead Selenide Nanocrystal Quantum Dots

Colloidal semiconductor particles constitute an important class of nanocrystal quantum dots (NQDs) that couple size-tunable optical properties with moleculelike chemical properties such as solubility, processability, and chemical reactivity. This chapter describes synthetic routes that are useful for obtaining large-size lead selenide quantum dots with demonstrated emission in the mid-IR. The key feature of the synthetic approach described in detail is the use of a two-step growth process. The first step involves nucleation and initial growth by rapid injection of lead and selenium precursors into a hot surfactant/solvent mixture. Additional particle growth to larger NQD sizes is accomplished in the second step that involves slow addition of precursors to the solution containing the "seed" particles. In this way, large-size lead selenide NQDs are obtained that possess optimized optical properties and minimal size dispersions.