Coated semiconductor nanoparticles (CSN) CdS/PbS in 60-80-Å diameter were fabricated by Pb2+ ions displacing Cd in Cd-S bonds on the surface of CdS single semiconductor nanoparticles (SSN) in CdS colloidal solution, although PbS has a different cubic crystalline structure than that of CdS. We use PVP (poly(vinylpyrrolidone)) as a stabilizing agent to control the size of CdS, PbS SSN, and CdS/PbS CSN. We investigated CdS/PbS nanoparticles' optical absorption and found that the excitation energy from the 1s hole state to the 1s electron state becomes smaller as the fraction of PbS shell in CdS/PbS CSN increases. Thus, we synthesize coated nanoparticles with continuously tunable energy gap from PbS SSNs to CdS SSNs. The CdS-PbS solid solution phase diagram indicates CdS-PbS solid solution system cannot be formed at room temperature. The observed microstructure of CdS/PbS CSN by transmission electron microscopy and the electron diffraction pattern by CdS/PbS CSN provides evidence that the particles are coated.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry