Raman scattering and luminescence emission of the CdSe/ZnS quantum dots mediated by the surface plasmon

The luminescence emission spectra show that there is a weak blue-shift effect for the CdSe/ZnS quantum dots (QDs) on the surface of the Ag thin film in comparison with the QDs on the Si substrate. The blue shift effect may be due to the enhanced biexciton luminescence emission because of the plasmon coupling. The surface plasmon coupling effect on the Raman scattering depends the size of the QDs. A strong surface enhanced Raman scattering (SERS) effect is observed for the QDs on the Ag thin film with the emission wavelength of 601.4 and 659.9 nm when the QDs are excited by a laser with the wavelength of 488 nm. The SERS effect is not observed for the QDs with the emission wavelength of 538.2 nm, because the excitation wavelength 488 nm is not in the high absorption waveband for the QDs. For the CdSe/Zns QDs on the Ag thin film a strong LO mode of CdS at 302 cm^-1 is observed in addition to the LO mode of CdSe at 212 cm^-1, which confirms that there is a structure of CdS at the interface of CdSe and ZnS in the CdSe/ZnS QDs.