Spectroscopic investigation of II-VI core-shell nanoparticles: CdSe/CdS

CdSe and CdSe/CdS core/shell nanoparticles were prepared by a one-pot synthesis process. The CdSe/CdS core/shell nanoparticles showed red-shift absorption and emission spectra compared to the CdSe core. An optimal reaction time for CdS to from oil the CdSe nanoparticles was evaluated and the highest photoluminescence yield of approximate to 20% was observed for the core/shell nanoparticles. Using nanosecond laser spectroscopy, the photoluminescence of CdSe nanoparticle was investigated and found to exhibit a monoexponential decay with a lifetime of 52.2 ns, while the photoluminescence of CdSe/CdS core/shell nanoparticles demonstrated biexponential decay characterized by a fast component around 25 ns and a slow component around 100 us. The Stokes shift, photoluminescence yield, and lifetimes were correlated and was attributed to the stress in the interface induced by the lattice mismatch of CdSe and CdS. The red-shift of the absorption and emission spectra of CdSe/CdS nanoparticles was discussed with the concepts of the quantum confinement and electronic confinement effects.