Surface-enhanced Raman scattering (SERS) for semiconductor microcrystallites observed in Ag-CdS hybrid particles

Nanostructural Ag-CdS hybrid particles are synthesized by a colloidal method. Physical development processes in a photographic technique have been modified to produce Ag-CdS nanostructural composite particles. Colloidal CdS particles with stabilizing surfactants are injected to a silver development solution. The core CdS particles initiate a nucleation of stable Ag small particles, and nanostructural composite aggregates of Ag-CdS particles precipitate in the solution. Surface plasmon absorption of Ag particles becomes broad, overlapping with a band edge absorption of CdS particles, indicating the coexistence of CdS and Ag particles in the solution, which was also confirmed by TEM photograph. A strong surface-enhanced Raman scattering (SERS) of CdS particles was observed in Ag-CdS colloidal nanocomposites, indicating novel optical response of CdS fine particles under a strong electric field from the surface plasma excitation of silver particles. Resonance effects in Ag-CdS hybrid aggregates where the band gap of CdS is almost equivalent to the excitation energy of the surface plasmon of Ag attract much interest in fundamental physics as well as device application points of view.