COATED SEMICONDUCTOR NANOPARTICLES - THE CDS PBS SYSTEMS PHOTOLUMINESCENCE PROPERTIES/

The photoluminescence (PL) spectra from colloidal solution of coated s emiconductor CdS/PbS nanoparticles, which are synthesized by a cation- exchanging colloidal method, are measured at room temperature. The PL spectra from S vacancies (V(S)) and Cd-S composite vacancies (V(Cd-S)) in CdS and CdS/PbS nanoparticles have been investigated. The PL of V( S) can be quenched only by the Pb caption modified in the surface of C dS. The PL Of V(Cd-S) in CdS nanoparticles appears in about 1100 nm. T he PL Of V(Cd-S) in CdS/PbS nanoparticles shifts to longer wavelengths as the quantity of PbS increases. The shift and intensity variation o f the PL peak from V(Cd-S) in CdS/PbS can be explained by a quantum co nfinement model of coated nanoparticles; the excited energy gap (HOMO- LUMO) is not only dependent on the size of the particles but also stro ngly dependent on the core/shell ratio of the coated nanoparticles. Th e PL energy gap (LUMO-V(Cd-S)) is also strongly dependent on the core/ shell ratio.