Over the past few years semiconductor nanocrystals (NCs) have attracted an increasing amount of interest for two main reasons. First of all, the sizes of these objects lie between that of molecules and that of crystalline materials. Consequently fundamental studies are most useful for helping to understand the properties of the condensed material as a function of the dimensions of the objects. In particular, the lead chalcogenide NCs possess high dielectric constants and charge carriers with small e ective masses. All this leads to the formation of excitons with large e ective Bohr radii. For this reason, these are choice systems for studying the regime of strong quantum con nement. Secondly, the miniaturization of electronic components requires the use of semiconductor objects of increasingly smaller dimensions, with the lowest possible fabrications costs. The semiconductor nanocrystals with generally simple chemical syntheses respond to this challenge and a certain number of applications are based on their optical properties. In a rst part of this thesis, a description is made of the techniques used for the synthesis of PbSe NCs. With the use of diverse techniques for characterization (electron microscopies, X-ray di raction (XRD), electron di raction (SAED)), optimization of the synthesis method led to the yield of NCs of monodispersed sizes and perfect crystal structures. In the second part, Raman spectroscopic studies con rmed the structural quality of the NCs and also made it possible to study the e ects of con nement on the spectra of the longitudinal optic phonons. Finally, as the PbSe NCs deteriorate rapidly in air, core shell structures were prepared in order to engineer the band in the heterostructural NCs. By using synchrotron radiation and after developing techniques for the deposit of ultra thin core shell PbSe/CdSe NC lms, photoelectron spectroscopic studies were undertaken of the discontinuity of the valence band of these structures.
