Surface-enhanced Raman scattering by CdS quantum dots

Surface enhanced Raman scattering is studied in nanostructures with CdS quantum dots formed by using the Langmuir-Blodgett technology. Features related to longitudinal optical phonons of quantum dots are observed in the Raman spectra of both free-standing CdS quantum dots and the dots embedded in an organic matrix. Strong enhancement of intensity (about factor of 700) of Raman scattering by free quantum dots is observed by deposition of silver clusters onto the nanostructure surfaces. The dependence of the Raman intensity on the excitation energy is resonant with a maximum at the energy corresponding to the maximal absorption of Ag clusters.