COATED SEMICONDUCTOR NANOPARTICLES - THE CDS/PBS SYSTEMS PHOTOLUMINESCENCE PROPERTIES

The photoluminescence (PL) spectra from colloidal solution of coated semiconductor 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 CdS. The PL Of V(Cd-S) in CdS nanoparticles appears in about 1100 nm. The PL Of V(Cd-S) in CdS/PbS nanoparticles shifts to longer wavelengths as the quantity of PbS increases. The shift and intensity variation of the PL peak from V(Cd-S) in CdS/PbS can be explained by a quantum confinement model of coated nanoparticles; the excited energy gap (HOMO-LUMO) is not only dependent on the size of the particles but also strongly dependent on the core/shell ratio of the coated nanoparticles. The PL energy gap (LUMO-V(Cd-S)) is also strongly dependent on the core/shell ratio.